international power steering series

®

Study Guide International ® Power Steering Series

TMT-050701

International® Power Steering Series

Study GuideTMT-050701

A NAV I STAR C O M PANY

©2007 International Truck and Engine Corporation4201 Winfield Road, Warrenville, IL 60555

All rights reserved.

No part of this publication may be duplicated or stored in an information retrieval system without the express written permission of

International Truck and Engine Corporation.

Introduction & Overview .................................................3

Program I: Pumps.............................................................9Overview ................................................................................................ 9Contaminated Fluid ............................................................................ 12Cavitation ............................................................................................. 14

Program II: Steering Gears ..........................................19Overview .............................................................................................. 19Sheppard Steering Gear .................................................................. 24TRW/Ross Advanced Steering Gears (TAS) .............................. 24Dual Steering Gears ..........................................................................25

Program III: Integrated Hydraulic Brake Booster ..........................................................33

Program IV: System Troubleshooting ........................43Diagnosing a Steering Complaint ..................................................45Power Steering Analysis ................................................................... 47

Program V: Common Service Procedures .................57Overview .............................................................................................. 57Lash Adjustment ................................................................................. 57Hard Steering ......................................................................................58Plungers/Poppet Valves ...................................................................59Steering Angle Alignment ................................................................60

Tandem Alignment ....................................................................60Toe-In Adjustment ....................................................................62Caster .........................................................................................62Camber .......................................................................................64

Table of Contents

2 International® Power Steering Series

Introduction �

Introduction & Overview

Welcome to the International® Power Steering training series. It is designed to provide all the technical knowledge and skill necessary to diagnose and repair the power steering system.

This series is divided into five programs. Programs I–III are designed to take you step by step through the operation of the pump, steering gear, and integrated hydraulic brake booster system. Program IV covers the techniques for troubleshooting these components. Program V concludes the Power Steering training series by providing some common service procedures.

Once you have successfully completed this DVD training series, you will have all the information you need to properly service International® power steering systems.

To receive credit for the completion of each program, you are required to take a post-test on ISIS®/Education/Service/Online Testing.

The two main parts of the power steering system are the pump and the gear. A hydraulic brake booster may also be installed in series with the system on a medium duty vehicle.

“The two main parts of the power steering system are the pump and the gear.”

“The two main parts of the power steering system are the pump and the gear.”


The key function of the system is to reduce steering effort through hydraulic power assist.

The basic theory of hydraulics is that liquids do not compress. If you apply force to a liquid in a closed system, the force is transmitted equally throughout the system.

In the case of a power steering system, the pump converts the rotational energy supplied by the engine into hydraulic energy for use by the steering gear. The gear is designed with hydraulic valves and passages that allow hydraulic pressure to assist in turning the wheels.

“The basic theory of hydraulics is that liquids do

not compress.”

“The basic theory of hydraulics is that liquids do

not compress.”

NOTES

Introduction 5

NOTES


®

Program I:Pumps


Program I: Pumps 9

Program I: Pumps

Overview

Although they’re manufactured by various suppliers, all International® power steering pumps are vane-type pumps, either belt or gear driven. The pumps on most current-production vehicles are gear-driven.

The main components of a pump are:

• The pump drive shaft

• Rotor

• Cam ring

• Vanes

• Valve spring and spool

• The pilot poppet

• And the pressure and delivery ports

The pump creates a partial vacuum at the inlet, which causes atmospheric pressure to force power steering fluid into the pump from the reservoir. The pump then pushes this fluid into the system to power the steering gear. The pressure and flow ratio of the pump depends on vehicle application.

Objectives

After completing this program, you will be able to:

• Identify power steering pump components.

• Describe the normal operation of power steering pumps.

• Identify the effects of contaminated or improper power steering fluid.

• Describe the effects of cavitation on power steering pump components.

Objectives


• Identify power steering pump components.

• Describe the normal operation of power steering pumps.

• Identify the effects of contaminated or improper power steering fluid.

• Describe the effects of cavitation on power steering pump components.


Let’s take a closer look at how it works. The pump’s rotor is driven within the cam ring by the drive shaft, which is connected to the engine. As the rotor turns, the vanes spin along the oval inner surface of the cam ring with a varying amount of offset from the rotor’s center. The spinning causes the chamber between the vanes to expand as the vanes pass the inlet section of the ring.

This creates a low-pressure condition, which forces hydraulic fluid into the chambers. This fluid is trapped between the vanes and carried past the large diameter of the ring.

As the fluid approaches the outlet section, the ring diameter decreases, forcing the fluid out into the system. Within the vane slots of the rotor, system pressure is routed to the backside of each vane. This action forces the vanes outward, keeping them sealed against the cam ring during normal pump operation.

The pump cam ring is shaped so that the two pumping chambers are formed exactly opposed to each other. Hydraulic forces cancel each other out and don’t impose side loading on the shaft.

“The pump cam ring is shaped

so that the two pumping chambers

are formed exactly opposed

to each other.”

“The pump cam ring is shaped

so that the two pumping chambers

are formed exactly opposed

to each other.”

Program I: Pumps 11

The pump has a pilot-operated, integral flow control and relief valve on the cover. An opening in the valve determines maximum pump delivery and system pressure. When the relief valve opens, the fluid is bypassed to the reservoir on a three-line pump design, or recirculated to the pump inlet on a two-line design. This limits the system to a prescribed maximum pressure.

During Low Speed, the total pump delivery can be passed through the opening. Pressure in this chamber equalizes pressure at the other end of the relief valve spool. The light spring holds the spool closed, and fluid from the pump is blocked from the tank port by the spool land.

When pump delivery is more than the opening allows, a pressure build-up forces the spool open against the light spring. Extra fluid is forced past the spool to the inlet port.

If pressure in the system builds up to the relief valve setting, the pilot poppet is forced off its seat.

Fluid in the large spring chamber flows through the spool and out to the tank. This causes a pressure differential on the spool, shifting it against the light spring. All the fluid can then flow to the tank.

As a failsafe, the relief valve setting is the same as the pump’s maximum system pressure. This design prevents excessive pressure to protect the power steering pump and related components.

NoteAs a failsafe, the relief valve setting is the same as the pump’s maximum system pressure. This design prevents excessive pressure to protect the power steering pump and related components.

Note


Contaminated Fluid

Vane pumps are built to close tolerances. Any contamination will cause damage that can lead to pump failure. For example, particles of dirt or sand in the fluid are abrasive and will score or wear the pump’s closely fitted parts.

Fluid contaminated with water or other liquids can rust the pump parts and housing. Rust will not only build up on the metal, but will also flake off into the fluid. All of these contaminants cause extra wear on parts, increasing the chances of internal leakage and reducing the pump’s efficiency.

Sludge is created when fluid reacts with excessive temperature changes or condensation.

It can build up on the internal parts and eventually plug the pump. The heat and friction could cause the pump parts to seize. Air, water, and heat can also create sludge through oxidation.

To ensure a contaminant-free environment, the fluid and filter should be changed according to the lubrication tables in the operator’s manual. Always use the recommended fluid for the vehicle you are working on.

There are NO serviceable parts within power steering pumps on International® vehicles.

NoteThere are NO serviceable parts within power steering pumps on International® vehicles.

Note

“Air, water, and heat can also create sludge

through oxidation.”

“Air, water, and heat can also create sludge

through oxidation.”

Program I: Pumps 1�

“Thin” or “worn out” fluid can be the result of extended drain intervals. Using the wrong type of fluid can cause many of the same conditions as “thin fluid,” including:

• Increased pump wear due to inadequate lubrication, leading to a loss of power assist,

• and reduced system pressure, also leading to a loss of power assist.

Improper maintenance techniques, such as failure to change the fluid and filter at the prescribed intervals, can cause the fluid to become too “thick,” potentially leading to:

• increased internal friction, which, in turn, will increase flow resistance through the system,

• increased temperature, which increases the chance of sludge build-up,

• and finally, more power will be required for operation.

The chemicals that make up some fluids can react unfavorably with the fibers or synthetic materials used in the pump packing and seals. This can lead to rapid deterioration, swelling, or shrinking of the seals and packings, resulting in both internal and external leakage.

The hydraulic brake system and Hydro-Max booster system are separate hydraulic systems. The hydraulic fluids used in each system are not compatible and cannot be mixed. Contamination of one fluid with the other will result in the deterioration of seals and hoses and lead to component damage.

CautioN!The hydraulic brake system and Hydro-Max booster system are separate hydraulic systems. The hydraulic fluids used in each system are not compatible and cannot be mixed. Contamination of one fluid with the other will result in the deterioration of seals and hoses and lead to component damage.

CautioN!


It is important that you refer to the operator’s manual or ISIS® for proper fluid type.

Cavitation

Poor maintenance and contaminated fluid can also lead to poor pump operation, resulting in pump cavitation. Cavitation occurs when the fluid does not entirely fill the pump as designed. The more common causes of cavitation are improper bleeding, air leakage on the suction side, or low fluid.

A pump that is allowed to continually cavitate will develop seriously worn parts, sluggish or erratic operation and loss of power steering assist. Eventually the pump parts may seize.

Another cause of cavitation is substituting a hose that is smaller in diameter than the original, which leads to excessive back pressure or pressure loss. This in turn allows air bubbles to form and create excessive heat, eventually causing the pump and seals to fail.

Using a hose made of material that doesn’t meet system standards could also cause problems. For example, an inadequate hose might burst or collapse, depending on whether it was installed on the pressure or suction

“Cavitation occurs when the fluid does

not entirely fill the pump as designed.”

“Cavitation occurs when the fluid does

not entirely fill the pump as designed.”

Program I: Pumps 15

side of the pump. Consequently, International® recommends the use of only OEM approved hoses and fittings.

Conclusion

This concludes Program I of the Power Steering training series. Completion of this educational process is a key component toward International® Technician Certification. You are now required to take a post-test via ISIS®/Education/Service/Online Testing.

NOTES


®

Program II:Steering Gears


Program II: Steering Gears 19

Program II: Steering Gears

Overview

International® uses both Sheppard and TRW/Ross Advanced Steering, or TAS, gears.

In this program, we’ll identify these brands and see how they work. We’ll also look at different system designs.

Unless a brand is specifically mentioned, the information presented here is an overview that applies to both brands of gears.

Integral power steering means that the gearbox contains a manual steering mechanism, a hydraulic control valve, and a hydraulic power cylinder, all in a single, compact package.

The gear provides full-time hydraulic steering. Only enough manual effort to overcome the torsion bar and to turn the rotary valve is required.

Integral steering gears are equipped with:

• A rotary control valve

• Rotating valve assembly

• Actuating, or input shaft

Objectives


• Identify and describe the operation of integral power steering TRW/Ross gears.

• Identify and describe the operation of integral power steering Sheppard gears.

• Identify and describe the operation of dual steering gears.

Objectives


• Identify and describe the operation of integral power steering TRW/Ross gears.

• Identify and describe the operation of integral power steering Sheppard gears.

• Identify and describe the operation of dual steering gears.


• Piston

• Sector shaft

• Bearing cap assembly

• Housing

• Slave gear on a dual steering system

• And a Steering column

Let’s look at what happens during a steering maneuver.

When a driver turns the wheel, he sends force from the steering wheel to the steering gear input shaft. The shaft is centered within the rotary valve by a torsion bar. The bar is pinned to the input shaft at one end and to the worm shaft at the other end. The bar turns with the input shaft, and also forces the worm shaft to rotate.

In response to this rotational force, the worm shaft, acting through the recirculating-ball mechanism, tries to move the rack piston axially through the gear-housing cylinder bore.

This movement is resisted by the rack piston’s engagement to the sector shaft, which is connected by a linkage to the road wheels.


Because of this resistance, the input shaft twists the torsion bar, thereby actuating the control valve. The control valve directs pressurized fluid to help move the rack piston axially through the cylinder bore. The rack piston then turns the sector shaft to steer the vehicle.

How fast the driver can turn the steering wheel using power assist depends on the pump flow directed to the cylinder. The pump flow is measured in gallons per minute, or gpm. The rotary control valve directs the flow of fluid through the steering gear.

The more pressure a steering gear can withstand, the more work it can perform. The maximum operating pressure for the TRW THP/PCF series is 2,688 psi at a maximum flow rate of 6 gpm while the Sheppard M-Series gear is 2,175 psi at 6 gpm.

Each vehicle manufacturer specifies the maximum operating pressure at which their various steering installations are to be operated. Refer to ISIS® for the correct pump relief settings for the truck you are working on.

If the truck is within its front-end weight rating, the steering gears can steer a vehicle through a turn at low vehicle and engine speed. As the driver turns the steering wheel faster

“The more pressure a steering gear can withstand, the more work it can perform.”

“The more pressure a steering gear can withstand, the more work it can perform.”


or slower, the gear will require more or less fluid. It is possible for the driver to turn the steering wheel too fast, causing more steering change than is desired, which is called an over steer condition. Refer to ISIS® for TAS series front-end weight ratings.

Let’s take a closer look at how oil flows through the gear.

When the steering wheel is turned, the actuating valve is opened in one direction. All the pressurized oil is applied to one end of the steering gear piston. This pressure build-up causes the piston to move.

When steering stops, the gear returns to the neutral, or non-steering, position. Whenever the engine is running there is constant low-pressure oil flow through the steering gear. The oil circulates at backpressure only and provides an instant response to steering wheel action, and also acts as a hydraulic cushion for the gear.

For example, if the wheels receive a shock load, the shock is transmitted through the sector shaft to the rack piston, and on to the worm shaft. The control valve sends high-pressure fluid to the correct cavity of the cylinder to absorb the road shock and help eliminate steering wheel kick.

“Whenever the engine is running there is constant low-pressure oil flow through the

steering gear.”

“Whenever the engine is running there is constant low-pressure oil flow through the

steering gear.”

Program II: Steering Gears 2�

Most gears are equipped with two unloading valves—also known as poppets or plungers. There is one at each end of the rack piston.

The valve in the direction of the turn will trip as the steered wheels come within 1/8–1/4 of an inch of the axle stops. These axle stops are factory set and should not require adjustment under normal circumstances.

The tripped valve reduces pressure in the gear and helps to reduce heat generated by the pump. At the same time, the valves also reduce back pressure forces on the steering linkage.

At the first full right and left turn of a newly installed steering gear, the poppet valves automatically set to the axle stops. Therefore no further adjustment of these valves should be necessary.

In addition to the poppet valves, steering gears are sometimes equipped with a relief valve which limits maximum supply pressure at the steering gear.

This optional part reduces system temperature by avoiding high-pressure bypass and recirculation flow within the pump. This is especially important when the pump is supplying pressurized fluid to an auxiliary component.

Care should be used when towing or moving a vehicle when the engine or hydraulic supply pump is not running.

CautioN!Care should be used when towing or moving a vehicle when the engine or hydraulic supply pump is not running.

CautioN!

If a sudden loss of pressure occurs during normal driving, the parts are designed to provide mechanical back-up steering so that the vehicle may be safely steered to the side of the road.

NoteIf a sudden loss of pressure occurs during normal driving, the parts are designed to provide mechanical back-up steering so that the vehicle may be safely steered to the side of the road.

Note

Automatic plungers are set at the factory and do not need to be re-set unless tire size is changed or wheel cut is extended.

NoteAutomatic plungers are set at the factory and do not need to be re-set unless tire size is changed or wheel cut is extended.

Note


It is worth noting that the relief valve does not reduce pressure as the wheels approach the axle stops since this function is carried out by the poppet valves.

Sheppard Steering Gear

Steering gears are identified by raised letters and numbers cast into the housing. In this case, the manufacturer is identified as “RH Sheppard”. The “Auto” designation indicates a gear housing spec designed for plungers that adjust automatically.

The serial number is stamped indicating the gear specifications and build date, each letter and number having a specific meaning. In this example, “P” means it’s a powered steering gear, “MX” is the “sequential model” designation, and the number � indicates a gear spec with auto plungers.

The numbers “06” mean the gear was manufactured in 2006, and the letter “I” indicates the month of September. “00944” is the sequential build number for this specific steering gear.

TRW/Ross Advanced Steering Gears (TAS)

Next is the TAS family of gears, manufactured by TRW.

If the customer’s complaint is reduced wheel cut, it may be necessary to check the axle stop settings using radius plates or turntables. For further assistance, call the International® Technical Service Help line at 1-800-336-4500.

NoteIf the customer’s complaint is reduced wheel cut, it may be necessary to check the axle stop settings using radius plates or turntables. For further assistance, call the International® Technical Service Help line at 1-800-336-4500.

Note

The following information identifies the family and specifications to which the steering gear belongs. It is important that the technician provide this information when completing the troubleshooting checklist and also when calling for technical assistance.

NoteThe following information identifies the family and specifications to which the steering gear belongs. It is important that the technician provide this information when completing the troubleshooting checklist and also when calling for technical assistance.

Note


Both the “date code” and “specification number” are stamped on the machined surface opposite the input shaft of this model 66 gear. The date code 26906 means the gear was built on the 269th day of 2006. Newer gears include a serial number after the date code.

An “A” at the end of the specification number, which is stamped above the date code, indicates a step bore housing.

For proper replacement parts, always reference the steering code found on the vehicle’s line setting ticket, or the International® part number stamped at the bottom of the machined surface.

When servicing other integral power steering gears, refer to ISIS® to correctly identify the date code and specification information for each gear type. Having the proper ID will also aid the technician when requesting support from the 1-800 Tech Line.

Dual Steering Gears

Two or more integral steering gears are sometimes used when there are high front axle loads. This is called a dual-steering system. It’s used to balance the steering gear output across two or more steering arms, and conserve under-hood space.

Bleeding of the dual steering system is critical whenever the oil has been changed, the system has been opened, or whenever a steering gear is replaced. Failure to bleed the steering system could result in an accident, injury or death. Refer to ISIS® for the proper bleeding procedures.

WarNiNg!Bleeding of the dual steering system is critical whenever the oil has been changed, the system has been opened, or whenever a steering gear is replaced. Failure to bleed the steering system could result in an accident, injury or death. Refer to ISIS® for the proper bleeding procedures.

WarNiNg!


In a dual steering gear system, both the master, or left, steering gear pitman arm and the slave, or right, steering gear pitman arm are mechanically linked to the front-end components by a drag link and steer arm at each knuckle. The slave gear assembly does not have an input shaft or an actuating valve.

Slave gears can become cold and sluggish in low ambient temperatures, leading to a possible complaint of noisy operation.

The noisy condition is non-damaging and normal on severe service or heavy duty vehicles that use 15W40 motor oil for power steering fluid. When the system is warmed up, the noise will dissipate.

Pressure to operate the slave gear is passed through ports in the cylinder head, sector shaft bore or bearing cap of the master gear. Fluid from the slave gear is returned to the master gear and back to the reservoir through pressure and return lines.

When the actuating shaft of the master gear moves, pressure builds on its piston. This same pressure is directed to the opposite end of the slave gear piston, causing the slave gear to operate in the opposite direction of

“Slave gears can become cold and sluggish

in low ambient temperatures.”

“Slave gears can become cold and sluggish

in low ambient temperatures.”


the master gear, assisting in the power steering operation of the system.

The slave gear does not have hydraulic relief plungers. When properly adjusted, master gear relief plungers will relieve hydraulic pressure for both gears.

When working on a Sheppard steering gear, it is important that the specified torque is applied to the retaining nut to force the pitman arm onto the sector shaft. This nut has the torque value stamped onto its face.

In addition, ensure the tabs are bent into their locked positions. If too much or too little torque has previously been used on the retaining nut, the pitman arm and sector shaft must be replaced.

On a TRW gear, a pinch bolt is used to secure the pitman arm to the sector shaft. Refer to ISIS® for the proper torque value.

There are three common dual system configurations with Sheppard M-Series steering gears:

• Cooling slave

• 92 Series (cooling) slave gears

• Standard slave

The Sheppard M-Series steering gear may also be used with an assist cylinder. Refer to ISIS® for operation, bleeding and repair procedures for hydraulic assist cylinders.

NoteThe Sheppard M-Series steering gear may also be used with an assist cylinder. Refer to ISIS® for operation, bleeding and repair procedures for hydraulic assist cylinders.

Note


The slaves operate the same way regardless of the configuration.

There are two ways to plumb a dual system, depending on the slave gear. Let’s look at some typical plumbing configurations.

With a typical dual M-Series steering gear layout, fluid simply circulates through the gear when there is no steering action. Fluid only goes to the slave gear when the steering wheel is turned.

Cooling Slave

Cooling slaves have a low pressure return port cast along the length of the slave gear housing. Return oil from the master gear is routed through this port and back to the reservoir. The additional line provides a cooling effect, as well as using the slave gear as a heat sink.

92 Series (Cooling) Slave

The 92 Series slave is plumbed the same way. Return oil is routed from the return side of the master gear through the sector shaft bore, then back to the reservoir. As with the cooling slave, the additional line provides a cooling effect and uses the slave gear as a heat sink.

“There are two ways to plumb a dual system, depending on

the slave gear.”

“There are two ways to plumb a dual system, depending on

the slave gear.”


Standard Slave

The M-Series standard slave gear requires only the crossover pressure lines between the master gear and the slave steering gear. An additional line is not required in the plumbing of the standard slave dual system.

Conclusion

This concludes Program II of the Power Steering training series. Completion of this educational process is a key component toward International® Technician Certification. You are now required to take a post-test via ISIS®/Education/Service/Online Testing.

NOTES

�0 International® Power Steering Series

®

Program III:Integrated Hydraulic

Brake Booster


Program III: Integrated Hydraulic Brake Booster ��

Program III: Integrated Hydraulic Brake Booster

The Hydro-Max booster assembly is composed of four basic parts:

• A hydraulically powered booster

• A reserve Electrical Hydraulic Pump, or EHP

• A hydraulic master cylinder

• And an integral flow switch

The Hydro-Max is a hydraulically powered brake booster that provides power assist for hydraulic brakes. A booster combined with a master cylinder forms the hydraulic brake actuation unit.

The Hydro-Max may be installed in series with the power steering gear. Due to their relative placement, the action of the brake booster influences the hydraulic pressure seen by the steering gear from the power steering pump.

In other words, the brake booster always receives the pressure and flow it needs. The steering gear uses the remaining pressure up to system relief pressure, which is the point where the pressure is high enough to trigger the relief valve.

Objectives


• Describe how the power steering system interacts with the hydraulic brake system.

• Describe the operation of the electric hydraulic pump (EHP).

Objectives


• Describe how the power steering system interacts with the hydraulic brake system.

• Describe the operation of the electric hydraulic pump (EHP).

Before working on the components that make up the Hydraulic Brake Booster and Power Steering System, refer to Technical Service Information, or TSI 04-04-01.

NoteBefore working on the components that make up the Hydraulic Brake Booster and Power Steering System, refer to Technical Service Information, or TSI 04-04-01.

Note

The hydraulic brake system and Hydro-Max booster system are separate hydraulic systems. The hydraulic fluids used in each system are not compatible and cannot be mixed. Contamination of one fluid with the other will result in the deterioration of seals and hoses and lead to reduced service.

CautioN!The hydraulic brake system and Hydro-Max booster system are separate hydraulic systems. The hydraulic fluids used in each system are not compatible and cannot be mixed. Contamination of one fluid with the other will result in the deterioration of seals and hoses and lead to reduced service.

CautioN!


Both the steering gear and booster are open center devices. Oil flows through the units continuously, varying only in the amount of pressure. Let’s take a closer look at how the brake booster operates.

Pressurized power steering fluid provides power assist to the brake master cylinder. During normal system operation, fluid flow from the power steering pump enters the inlet or pressure port of the Hydro-Max booster. It flows through the throttle valve and power piston, then through the flow switch and exits at the outlet, or return, port.

When the driver depresses the brake pedal, the pedal arm moves the pedal pushrod of the Hydro-Max unit. This movement closes the throttle valve, restricting flow. The flow restriction increases pressure on the booster piston, and sends a boosted force to the master cylinder primary piston.

An output pushrod transmits the force from the booster piston to the master cylinder primary piston. A reaction piston inside the booster-piston subassembly provides the driver with “pedal feel” when the brakes are applied.

“Pressurized power steering fluid

provides power assist to the brake

master cylinder.”

“Pressurized power steering fluid

provides power assist to the brake

master cylinder.”

Program III: Integrated Hydraulic Brake Booster �5

When the driver releases the brake pedal, the cut-in spring opens the throttle valve, relieving the pressure behind the booster piston. Return springs on both the booster piston and the master cylinder return these pistons to their released positions.

The electric hydraulic pump, or EHP, is mounted on the bottom of the booster assembly. If the normal flow from the power steering pump is interrupted—from engine-driven pump failure, engine failure or something else—the EHP provides the power for reserve stops.

The basic signal for operation of the EHP comes from the integral flow switch. When there is an interruption, the integral flow switch closes, energizing a power relay that provides electrical power to the EHP.

During this “back-up” operation, the EHP recirculates fluid within the booster assembly, building pressure on-demand through the throttle valve. The inlet port check valve keeps the fluid in the booster.

Since the fluid only circulates within the Hydro-Max booster unit, the EHP cannot provide any assist for the power steering system.

The boost pressure provided by the EHP is less than half of the primary system boost. Drive the vehicle cautiously to the nearest service facility for repairs if the brake system is in a failed condition, or the brake indicator light is on. Refer to TSI 04-04-01 regarding the status of the warning light.

NoteThe boost pressure provided by the EHP is less than half of the primary system boost. Drive the vehicle cautiously to the nearest service facility for repairs if the brake system is in a failed condition, or the brake indicator light is on. Refer to TSI 04-04-01 regarding the status of the warning light.

Note


The EHP also operates when the engine is stopped and the driver is applying the brakes, providing limited brake power assist when the truck is not running.

The master cylinder is a split system type with separate fluid chambers, pistons and outlet ports for the front and rear brake circuits. A differential pressure switch, fluid level indicator switch, and remote reservoir are also available.

The power steering gear must be balanced so that it can handle the pressures generated in the steering gear return line. Its internal relief valve setting needs to be lower than the pump’s relief valve setting. The fluid flow path is required to minimize the interaction between the power steering gear and the hydraulic booster.

Now, we’ll look at fluid pressure through the system during:

• standard steering,

• brake application,

• severe steering and simultaneous braking,

• and during maximum wheel steering or full lock.

“The power steering gear must

be balanced so that it can handle

the pressures generated in the

steering gear return line.”

“The power steering gear must

be balanced so that it can handle

the pressures generated in the

steering gear return line.”


When the driver steers the truck, the steering gear control valve shifts. This causes pressure to rise in the pump, steering gear supply line and gear upper cylinder cavity.

This pressure differential across the steering gear piston causes it to move toward low pressure, displacing the lower end oil to the return port. This oil is under low pressure—its flow back to the reservoir is only impeded by the slight restrictions in the plumbing and neutral position of the brake booster.

At this point, pressure in the steering gear builds to 1,500 psi. But because the steering gear uses 50 psi itself, there is a loss of 50 psi between the inlet and outlet, meaning that there is 1,450 psi remaining to perform work.

The brake booster is performing no work, meaning there is no change in pressure from the inlet to the outlet. Therefore, the power steering pump is subjected to the highest pressure in the hydraulic circuit.

Now let’s look at system flow during brake application, without any steering. When the driver applies the brakes, the control valve in the brake booster shifts. In this case, pressure rises in the booster, steering gear and power steering pump. The pressure differential


across the booster piston moves the piston toward low pressure, actuating the brake master cylinder pushrod. Fluid flows from the booster back to the reservoir under little pressure.

At this point, the steering gear is performing no work, meaning there is no pressure difference between the inlet and outlet. The brake booster uses 900 psi. The booster ports use 50 psi, so the total work performed is 850 psi.

If a driver makes a severe steering maneuver while braking, pressure in the steering gear supply line will rise to a maximum of 1,850 psi before the steering gear relief valve actuates, limiting the pressure.

At this point the steering gear is capable of work equivalent to 1,850 psi. The booster takes on 900 psi and the booster ports use up 50 psi, so the actual work performed by the brake booster is 850 psi. This leaves 950 psi of work for the steering gear.

Power steering capability is reduced in this mode compared with the steering-only mode—here’s why:

Oil keeps moving through the circuit since the system relief valve in the steering gear directs fluid to the return


port and downstream to the brake booster.

If the power steering pump relief valve is actuated during this mode, the oil flow would stop in the steering gear and brake booster circuits. This would result in starting up the EHP in the brake booster, leaving the driver with essentially manual steering capability.

During a steering maneuver near full steering lock, the poppet unloading valves actuate, relieving pressure across the steering gear piston. Fluid keeps flowing into the steering gear and out the return line to the brake booster. When the brake booster is fully actuated, pressure in the line between the steering gear and brake booster will rise to 900 psi.

Conclusion

This concludes Program III of the Power Steering training series. Completion of this educational process is a key component toward International® Technician Certification. You are now required to take a post-test via ISIS®/Education/Service/Online Testing.

NOTES


®

Program IV:System Troubleshooting


Program IV: System Troubleshooting 4�

Program IV: System Troubleshooting

As we begin power steering system inspection, diagnostics, and repair, keep in mind that proper service techniques, environmental concerns and safety are the most important parts of this process

When performing service work of any kind, always protect the interior of the vehicle by using a paper floor mat, a steering wheel cover, and a seat cover.

When working on the power steering system, keep the work area and tools as clean as possible. Also, clean all connections before disconnecting or removing components.

Use a suitable pan to catch any fluid when disconnecting components.

All power steering component and line openings should be immediately plugged during removal and remain so until reinstallation to prevent contamination by dirt, moisture or other foreign material. Even the slightest particle can cause unexpected problems within the power steering system.

Objectives


• Describe the troubleshooting procedure for International® power steering systems.

• Identify and use a Power Steering Checklist.

Objectives


• Describe the troubleshooting procedure for International® power steering systems.

• Identify and use a Power Steering Checklist.

Before beginning diagnostic or service procedures, always shift the transmission to park or neutral, set the parking brake and block the wheels.

WarNiNg!Before beginning diagnostic or service procedures, always shift the transmission to park or neutral, set the parking brake and block the wheels.

WarNiNg!

Always provide proper ventilation when operating an engine in an enclosed area. Inhalation of exhaust gases can be fatal.

WarNiNg!Always provide proper ventilation when operating an engine in an enclosed area. Inhalation of exhaust gases can be fatal.

WarNiNg!


Be sure that you know the location of properly rated and charged fire extinguishers.

Be sure you know the location of an emergency eyewash station.

Be sure to follow each warning, caution, and note as they are presented throughout this training program.

Warnings indicate procedures and safety measures that must be followed precisely to avoid the risk of death or personal injury to yourself or other shop personnel, and to avoid damage to the vehicle, equipment or components.

Cautions indicate a procedure that you must follow exactly to avoid equipment or component damage.

Notes indicate operations, procedures or instructions that are important for proper service.

The following tools will be helpful to properly troubleshoot steering complaints:

• A torque wrench,

• A thermometer,

• A ZTSE2780 Power Steering Analyzer,

When working on the power steering system, always wear safety glasses with side shields and chemical-blocking nitrile gloves.

WarNiNg!When working on the power steering system, always wear safety glasses with side shields and chemical-blocking nitrile gloves.

WarNiNg!

Program IV: System Troubleshooting 45

• And a ZTSE4402 Plug for the TRW Steering Gear.

The ZTSE tools are available from Kent-Moore.

You’ll also need the ��1812K Plug for the Sheppard steering gear. This is available from the International® PDC.

Diagnosing a Steering Complaint

This program is designed to help you troubleshoot steering complaints so the proper service procedures can be performed where necessary.

To properly diagnose a steering complaint, it is important to understand the complaint.

Talk to the driver and get specific details:

• When does the problem happen?

• When was it first noticed?

• Does the problem happen when the truck is loaded or empty?

Also, be aware that overloaded front axles and tires may cause intermittent hard steering feel. The better you understand the circumstances, the better your ability to solve the problem.


After meeting with the driver to verify the complaint as written by the service advisor, conduct a general walk around visual inspection.

First inspect the fifth wheel to ensure that it is adequately lubricated. Check for correct tire pressures and unusual tire wear on all axles. Inspect the tie rod for damage and worn ends. Check the mounting of the steering gear for looseness.

Next, inspect the U-joints and slip joint of the I-shaft for any looseness and lubricate if necessary. Also inspect the drag link for any looseness. Before inspecting the king pins for wear and binding, disconnect the drag link from the pitman arm.

Next, inspect the hydraulic system for the correct fluid level, condition, and any leakage. Discolored or burnt-smelling fluid may indicate neglected maintenance, or operating temperature that is too high. Under these circumstances, it is recommended that the fluid be changed in conjunction with a new filter.

Carefully inspect the power steering hoses for proper routing and condition. Pay close attention to the supply hose from the reservoir to the pump. This hose is critical and is sometimes

While the drag link is disconnected, do not turn the steering wheel more than one and a half turns as this will require resetting of the poppets.

NoteWhile the drag link is disconnected, do not turn the steering wheel more than one and a half turns as this will require resetting of the poppets.

Note


overlooked in steering diagnosis. The hose should be free of sharp bends and pliable without being spongy.

If the complaint is thought to be a component issue, a supply hose that doesn’t provide fluid to the pump during all operating conditions could be the cause.

For example, high back pressure can result when a supply hose is restricted, kinked or closed off during high pump rpm. This will prevent adequate fluid supply to the pump during the power steering flow test, which could cause periodic loss of power steering assist or hard steering.

You must perform all tests in the steering troubleshooting checklist for proper diagnosis. Record the data on the checklist and compare the test results with the customer’s complaint. Refer to TSI 02-05-01 found on ISIS® to print a copy of this checklist.

Power Steering Analysis

Before beginning the analysis, it is important to connect and prep the power steering analyzer as follows:

• First, with the engine off and the vehicle level and resting normally on all four tires, install the analyzer in

Watch the power steering analyzer pressure gauge closely when closing the shutoff valve. A bad relief valve may not relieve the pump pressure and can cause pump damage or a high-pressure hose to rupture. If pressure rises rapidly or goes above 2,500 psi, STOP.

WarNiNg!Watch the power steering analyzer pressure gauge closely when closing the shutoff valve. A bad relief valve may not relieve the pump pressure and can cause pump damage or a high-pressure hose to rupture. If pressure rises rapidly or goes above 2,500 psi, STOP.

WarNiNg!


series between the pressure side of the power steering pump and the pressure side of the steering gear. When properly connected, the flow meter arrow will point toward the steering gear. Fill the power steering reservoir to the proper level.

• Next, start the engine. Verify that both the pressure gauge needle and flow meter move in the direction of oil flow. If they don’t, the power steering analyzer has been installed backwards.

• Finally, bleed the system of any air and ensure that the reservoir is still filled to the proper level.

Since oil temperature affects the performance of hydraulic components, it is important that a suitable thermometer be installed in the power steering reservoir when conducting this test.

Begin the test by first measuring and recording the temperature. Tests should be performed at system operating temperatures of 180°F (82°C).

However, if the driver complains of an intermittent problem, it may be necessary to raise the oil temperature to 220°F (104°C) for testing. To achieve this temperature, partially close off the valve on the power steering analyzer


to 1,500 psi long enough to raise the temperature, then fully open the valve.

Next, measure and record system backpressure. Do this by reading the pressure on the gauge with the wheels straight, and no steering wheel input. Test the maximum system pressure by closing and opening the power steering analyzer valve quickly three times. Then record the maximum—or pump relief—pressure on the Troubleshooting Checklist.

Do not leave the valve closed for more than a few seconds. This will cause internal damage to the pump.

Now measure and record the flow at idle, backpressure only. This is read in gallons per minute with the valve all the way open. Then measure and record the flow at idle with 1,500 psi load applied by closing the valve to read 1,500 psi on the gauge.

Open the valve and with the assistance of a second technician to work the engine throttle, measure and record maximum engine rpm. Then measure and record the flow at idle with 1,500 psi load applied by closing the valve to read 1,500 psi on the gauge. Open the valve and bring engine rpm back to an idle when the tests are completed.

“Test the maximum system pressure by closing and opening the power steering analyzer valve quickly three times.”

“Test the maximum system pressure by closing and opening the power steering analyzer valve quickly three times.”


With the assistance of a second technician using a normal “hand over hand” technique, have him turn the steering wheel at idle while you watch the gauge needle carefully. Record the peak static steering pressure values on left and right turns, just before the pressure drops off.

Next, with the engine at idle, use an in.-lb. torque wrench to measure and record the static steering input effort to turn the steering wheel on left and right turns. Refer to ISIS® for the horn cover removal procedures specific to the vehicle you are working on. On a Sheppard M series steering gear, the input effort can be as high as 80–100 in.-lbs. of torque. Refer to TSI 92-05-0�, found on ISIS®.

After you complete the tests, you need to evaluate the results. To do this, it is important to understand pump specifications.

Each pump is designed for specific applications and performance. Changing pumps to a different specification is not recommended without International® engineering approval.

In addition, each model of steering gear has flow and pressure recommendations. Refer to ISIS® for

“Each model of steering gear has flow and pressure

recommendations.”

“Each model of steering gear has flow and pressure

recommendations.”


the specifications of the steering gear being serviced.

If pump flow is lower than the minimum for the specific gear, you could experience a hard steer condition or intermittent loss of power assist.

If the test results are within specifications and the cause of the steering complaint is not discovered, you may have to perform a steering gear internal leakage test.

First, check to see if the steering gear is fitted with a pressure relief valve. These will typically be found on 1000, 2000, �000, 4000 and 8000 series vehicles.

A 11/4 inch nut on the input end cap identifies the pressure-relief valve. To properly test this type of gear, remove the relief valve and install a special plug.

The plug part number for a Sheppard gear is ��1812K. The plug for a TRW gear is part number ZTSE4402.

Next, install a 4 x 4 wooden block long enough to fit between the tire and wheel and the chassis frame rail. This is to test the steering gear leakage at maximum pump delivery.

Place the block of wood in contact with the tire and wheel evenly. Place the

“This test will bring the system to maximum pump pressure.”

“This test will bring the system to maximum pump pressure.”


other end against the frame rail. Instruct a second technician to turn the steering wheel in the direction of the block. This test will bring the system to maximum pump pressure.

Read the flow meter. If the flow is more than 1 gpm, the gear has excessive internal leakage.

To view the troubleshooting charts refer to the appropriate service manual sections found on ISIS®.

For technical assistance in steering performance diagnostics, refer to ISIS® for the TSI and Warranty Policy letters.

Conclusion

This concludes Program IV of the Power Steering training series. Completion of this educational process is a key component toward International® Technician Certification. You are now required to take a post-test via ISIS®/Education/Service/Online Testing.

NOTES

Program IV: System Troubleshooting 5�

NOTES


®

Program V:Common Service Procedures


Program V: Common Service Procedures 57

Program V: Common Service Procedures

Overview

The following tools may be needed to complete these common repair procedures. For a general steering gear you will need:

• A magnetic base from a dial indicator,

• A tandem alignment caliper,

• A toe-in gauge,

• And a torque wrench.

Lash Adjustment

The first procedure involves checking the sector shaft for proper adjustment and then performing a lash adjustment.

First, set the sector shaft on the center of travel or high point.

Then remove the drag link.

Next, check for sector shaft lash, or endplay, by grasping the pitman arm and gently trying to rotate it. Looseness at this point indicates a sector shaft that is out of adjustment. To achieve proper adjustment, first loosen the jamb nut

Objectives


• Identify and perform common repair procedures related to power steering systems on International® trucks.

Objectives


• Identify and perform common repair procedures related to power steering systems on International® trucks.

Always use a new pinch bolt and nut whenever reinstalling the steering column to the steering gear.

CautioN!Always use a new pinch bolt and nut whenever reinstalling the steering column to the steering gear.

CautioN!

While the drag link is disconnected, do not turn the steering wheel more than one and a half turns as this will require resetting of the poppets.

NoteWhile the drag link is disconnected, do not turn the steering wheel more than one and a half turns as this will require resetting of the poppets.

Note


and then slowly turn the shaft adjusting screw clockwise until you feel no play at the sector shaft.

Next, continue turning the screw clockwise an additional 1/8–�/16 turn. While holding the adjusting screw in place, tighten the jam nut to the specifications found on ISIS®.

Finally, check for play by turning the steering wheel left to right, 1/4 turn off-center. You shouldn’t feel any endplay.

For more information, go to “Power Steering Gear: TRW/Ross TAS, 40, 55, 65 and 85” on ISIS®.

Hard Steering

If the driver complains that the truck is hard to steer in both directions, your task is to determine the fault and repair it. Refer to the “Power Steering Diagnostics” information as shown previously in this series or on ISIS®, TSI 02-05-01.

Some possible causes for a hard steering complaint are:

• a faulty supply pump,

• improper axle and front end alignment,

• high operating temperature,

This adjustment can only be completed on the vehicle if the adjusting screw and its jamb nut are accessible. This screw and nut are located on the side cover of the gear.

NoteThis adjustment can only be completed on the vehicle if the adjusting screw and its jamb nut are accessible. This screw and nut are located on the side cover of the gear.

Note


• foreign matter clogging piston relief,

• low oil level,

• air in the system,

• a front end load that is too heavy,

• or bent or damaged tie rods or king pins.

Plungers/Poppet Valves

Plungers or poppet valves need to be adjusted if:

• larger tires have been placed on the truck,

• there is reduced vehicle wheel cut, also known as turning angle,

• originally a pitman arm was mistimed and then the condition was corrected,

• the steering gear is being installed on a different truck,

• the steering axle stop bolts have been bent or broken,

• or the steering axle U-bolts have been bent or broken.

Refer to ISIS® regarding vehicle poppet readjustment for RH Sheppard and TAS power steering gears.


Steering Angle Alignment

Now we’ll discuss steering angle alignment and how it affects steering and vehicle handling.

Tandem Alignment

First, let’s define tandem alignment.

If the front axle has heavy tire wear on the outside of one tire and the inside tread of the other, inspect the tandem rear axle suspension alignment.

Tandem alignment can affect steering if the tandems are not parallel to the front axle. The truck may pull one direction or the other, depending which direction it’s misaligned.

The approved method of tandem alignment is through the use of a laser-type alignment device. But the following method will give you a ballpark reading that will help diagnose a steering complaint.

Begin by driving the vehicle forward, then backward a few feet. Do this at least twice. Use light brake pressure if necessary. Next, roll forward slowly about 20 inches. Don’t use the brakes to stop, because they may grab, jar the suspension, and prevent good measurements.

Always use safety stands with hydraulic jacks or hoists. Do not rely on jacks or hoists alone to carry the load; they can fail.

WarNiNg!Always use safety stands with hydraulic jacks or hoists. Do not rely on jacks or hoists alone to carry the load; they can fail.

WarNiNg!

In the absence of a laser alignment system, the use of a string for tandem and front axle alignment provides a straight line reference for accurate measurement.

NoteIn the absence of a laser alignment system, the use of a string for tandem and front axle alignment provides a straight line reference for accurate measurement.

Note


Place a pair of jack stands about 6 feet in front of the truck, in line with the steer wheels. Tie a string to the jack stand on the right side so that it’s on the outside centerline of the wheel on the same side.

Next, run the string back and between the tandems, up to the front and attach it to the other jack stand.

Move the driver’s side stand in until the string just touches the outside centerline of the wheel on this side.

Attach a magnetic base from a dial indicator to the center of the drive axle flange of the front tandem on the driver’s side.

Measure and record the distance between the center of the front axle hub and the center of the front tandem on the driver’s side. Perform the same measurement on the passenger side and record the reading.

If the two measurements are within 1/8–1/4 inch, the tandem is aligned with the front axle.

Use a tandem alignment caliper to check rear tandem alignment to the front tandem by measuring from center to center of the rear tandems. Do this on both sides of the vehicle


and compare the measurements. The tandem axles are in alignment if the measurements are within 1/8 inch.

For more details about rear axle alignment, refer to TSI 9�-14-01 on ISIS®.

Toe-In Adjustment

The toe-in adjustment is the most important alignment factor to check when attempting to extend tire wear. Toe-in is the amount—in fractions of an inch—that the front wheels are closer together at the front than at the back as viewed from the top of the truck.

When the vehicle is driven, the forces acting on the front wheels tend to make the wheels toe-out. To overcome this condition, the wheels are given a certain amount of toe-in.

Incorrect toe-in will result in rapid tire wear. Excessive toe-in will produce a scuffing or a leather-edge at the outside edge of both tire treads.

For more information about toe-in setting, refer to TSI 04-02-01 on ISIS®.

Caster

Caster is the amount, in degrees, the top of the kingpin leans toward the front

“Incorrect toe-in will result in

rapid tire wear.”

“Incorrect toe-in will result in

rapid tire wear.”

Program V: Common Service Procedures 6�

or rear of the truck, as viewed from the side of the truck. The angle can range from positive to negative.

Positive caster is the tilting of the top of the kingpin toward the rear of the truck. Negative, or reverse, caster is the tilting of the top of the kingpin toward the front of the truck.

Positive caster imparts a trailing action to the front wheels, while negative caster causes a leading action. The correct amount of caster helps to keep the front wheels in the straight-ahead position.

Positive caster acts as a lever, assisting the driver to return the front wheels to the straight-ahead center position. However, the truck will pull to the side with overly negative caster.

Caster specifications are based on vehicle design load with no payload, which usually results in a level frame.

Possible causes of incorrect caster are sagging springs, a bent or twisted axle, or unequally tightened spring U-bolts.

Caster on the passenger side must have a higher degree angle than the driver’s side, but the difference should not be more than one degree. This accommodates the crown of the road.

If the frame is not level when alignment checks are made, this must be considered in determining whether the caster setting is correct. The use of a bubble protractor is recommended to complete this task.

NoteIf the frame is not level when alignment checks are made, this must be considered in determining whether the caster setting is correct. The use of a bubble protractor is recommended to complete this task.

Note


In most cases, if caster varies more than the specified one degree between the left and right sides, it’s caused by a twisted axle.

If caster must be corrected, tapered shims can be used as needed between the springs and axle. Spring U-bolts should be tightened evenly and to the specified torque after the addition or removal of shims.

To increase caster, insert the wedge so the thick end faces the rear of the truck. To decrease caster, place the wedge so that the thick end is toward the front of the truck.

If an excessively thick wedge is required for a truck that has high mileage, check the contour of the springs and replace the springs if necessary. Refer to ISIS® for further details on how to measure and adjust for an incorrect caster setting.

For more details about caster, refer to TSI 04-02-01 on ISIS®.

Camber

Camber is the amount, in degrees, that the wheel tilts away from vertical at the top, as viewed from the front of the truck. It is determined by the kingpin angle built into the axle.

“If caster must be corrected,

tapered shims can be used.”

“If caster must be corrected,

tapered shims can be used.”


Because the camber angle is set at the manufacturing plant, it is not recommended that the front axle be bent to change the camber angle. Positive camber is an outward tilt of the tires, while negative, or reverse, camber is an inward tilt.

An incorrect camber angle causes the side of the tread to wear. If camber angle is found to be wrong, it is an indication of a bent or improperly installed axle. Unequal camber in the front wheels may cause the truck to pull to the side that has the most positive camber.

To ensure that the front axle is properly installed, it is important to note that the name tag or the word “front” must go to the front of the truck. Mark the axle if necessary for reassembly.

For more details about camber, refer to TSI 04-02-01 on ISIS®.

Conclusion

This concludes Program V of the Power Steering training series. Completion of this educational process is a key component toward International® Technician Certification. You are now required to take a post-test via ISIS®/Education/Service/Online Testing.

“An incorrect camber angle causes the side of the tread to wear.”

“An incorrect camber angle causes the side of the tread to wear.”

NOTES


international power steering series

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