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CHAPTER 9

Lubrication System Operation

and Diagnosis

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Automotive Engine Performance, 3/e

By James D. Halderman

Copyright 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 All rights reserved. 2

After studying Chapter 9, the reader will be able to:

1. Prepare for Engine Repair (A1) ASE certificationtest content area D (Lubrication and Cooling

Systems Diagnosis and Repair).

2. Explain engine oil ratings.

3. Describe how an oil pump and engine lubrication

work.

4. Discuss how and when to change the oil and

filter.5. Explain how to inspect an oil pump for wear.

OBJECTIVES

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KEY TERMS

boundary lubrication

Hydrodynamic lubrication Longitudinal header

oil gallery

positive displacement

pump pressure regulating valve

viscosity

windage tray

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LUBRICATION PRINCIPLES

Engine oil is the lifeblood of any engine.

The purposes of engine oil include the following: Lubricating all moving parts to prevent wear

Helping to cool the engine

Helping to seal piston rings Cleaning, and holding dirt in suspension in the oil

until it can be drained from the engine

Neutralizing acids that are formed as the result of

the combustion process Reducing friction

Preventing rust and corrosion

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Lubrication between two

moving surfaces resultsfrom an oil film that

separates the surfaces and

supports the load.

FIGURE 9

1 Oil molecules cling to metal

surfaces but easily slide against each other.

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FIGURE 92 Wedge-shaped oil film developed below a moving block.

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FIGURE 93 Wedge-shaped oil film curved around a bearing journal.

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OIL PUMPS

All production automobile

engines have a full-pressure oil system.

The oil is drawn from the

bottom of the oil pan and is

forced into the lubrication

system under pressure.

In most engines that use a

distributor, the distributor

drive gear meshes with a

gear on the camshaft.

FIGURE 94An oil pump driven by the camshaft.

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OIL PUMPS

FIGURE 95 The operation of a rotor-type oil pump.

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OIL PUMPS

FIGURE 96A typical oil pump mounted in the front cover

of the engine that is driven by the crankshaft.

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OIL PUMPS

FIGURE 97 Gerotor-type oil pump driven by the

crankshaft.

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OIL PUMPS

FIGURE 98 In a gear-type oil pump, the oil flows through the pump around

the outside of each gear. This is an example of a positive displacement pump,

where everything entering the pump must leave the pump.

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OIL PRESSURE REGULATION

In engines with a full-pressure lubricating system,

maximum pressure is limited with a pressure reliefvalve.

The relief valve (sometimes called the pressure

regulating valve) is located at the outlet of the

pump.

The relief valve controls maximum pressure by

bleeding off oil to the inlet side of the pump.

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FIGURE 99 Oil pressure relief valves are spring loaded. The stronger the spring

tension, the higher the oil pressure.

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FIGURE 910A typical engine design that uses both pressure and splash lubrication. Oil travels under

pressure through the galleries (passages) to reach the top of the engine. Other parts are lubricated as

the oil flows back down into the oil pan or is splashed onto parts.

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FACTORS AFFECTING OIL PRESSURE

As the engine parts wear and clearance becomes

greater, more oil will leak out. The oil pump capacity must be great enough to

supply extra oil for these leaks.

The capacity of the oil pump results from its size,

rotating speed, and physical condition.

If the pump is rotating slowly as the engine is

idling, oil pump capacity is low.

If the leaks are greater than the pump capacity,engine oil pressure is low.

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The viscosity of the engine oil affects both the

pump capacity and the oil leakage. Thin oil or oil of very low viscosity slips past the

edges of the pump and flows freely from the leaks.

Hot oil has a low viscosity, and therefore, a hot

engine often has low oil pressure.

Cold oil is more viscous (thicker) than hot oil.

This results in higher pressures, even with the cold

engine idling.

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High oil pressure occurs with a cold engine,

because the oil relief valve must open farther torelease excess oil than is necessary with a hot

engine.

This larger opening increases the spring

compression force, which in turn increases the oilpressure.

Putting higher-viscosity oil in an engine will raise

the engine oil pressure to the regulated setting ofthe relief valve at a lower engine speed.

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OIL PUMP CHECKS

The cover is removed to check the condition of the

oil pump. The gears and housing are examined for scoring.

If the gears and housing are heavily scored, the

entire pump should be replaced.

If they are lightly scored, the clearances in the

pump should be measured.

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OIL PUMP CHECKS

FIGURE 911 (a) A visual inspection indicated that this pump cover was worn. (b) An embedded

particle of something was found on one of the gears, making this pump worthless except for scrap

metal.

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OIL PASSAGES IN THE BLOCK

From the filter, oil goes through a drilled hole that

intersects with a drilled main oil gallery orlongitudinal header.

This is a long hole drilled from the front of the

block to the back.

Inline engines use one oil gallery; V-type engines

may use two or three galleries.

Passages drilled through the block bulkheads

allow the oil to go from the main oil gallery to themain and cam bearings.

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OIL PASSAGES IN THE BLOCK

FIGURE 913An intermediate shaft

drives the oil pump on this overhead

camshaft engine. Note the main

gallery and other drilled passages in

the block and cylinder head.

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VALVE TRAIN LUBRICATION

The valve train components are the last parts to

get oil from the oil pump. The oil gallery may intersect or have drilled

passages to the valve lifter bores to lubricate the

lifters.

When hydraulic lifters are used, the oil pressure in

the gallery keeps refilling them.

On some engines, oil from the lifters goes up the

center of a hollow pushrod to lubricate the pushrodends, the rocker arm pivot, and the valve stem tip.

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VALVE TRAIN LUBRICATION

FIGURE 914 Oil is sent to the rocker arms on this Chevrolet V-8

engine through the hollow pushrods. The oil returns to the oil pan

through the oil drainback holes in the cylinder head.

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OIL PANS

As the vehicle accelerates, brakes, or turns

rapidly, the oil tends to move around in the pan. Pan baffles and oil pan shapes are often used to

keep the oil inlet under the oil at all times.

As the crankshaft rotates, it acts like a fan and

causes air within the crankcase to rotate with it.

A baffle or windage tray is sometimes installed in

engines to eliminate the oil churning problem. This

may be an added part,

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OIL PANS

FIGURE 915A typical oil pan with a built-in windage tray used

to keep oil from being churned up by the rotating crankshaft.

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OIL PANS

FIGURE 916A straightedge

and a feeler gauge are being

used to check that the oil pan

has been correctly installed on

the 5.7-liter Chevrolet V-8engine. The oil pan is part of the

engine itself and must be

properly installed to ensure that

other parts attached to the

engine are not being placed in a

bind.

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OIL COOLERS

Oil temperature must also

be controlled on many

highperformance or

turbocharged engines.

FIGURE 917A typical engine oil cooler. Engine

coolant flows through the cooler adjuster that fits

between the engine block and the oil filter.

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OIL PRESSURE WARNING LAMP

All vehicles are equipped with an oil pressure

gauge or a warning lamp. The warning lamp comes on whenever the engine

oil pressure has dropped to 3 to 7 PSI.

Normal oil pressure is considered to be 10 PSI per

1,000 RPM.

An electrical switch is used to convert the ground

circuit of the oil pressure warning lamp if the oil

pressure is below the rating of the sending unit.

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FIGURE 918 The oil pressure switch is connected to a warning lamp that alerts

the driver of low oil pressure.

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FIGURE 919A typical oil pressure sending unit on a Ford V-8.

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What Is Acceptable Oil Consumption?

There are a number of opinions regarding what isacceptable oil consumption. Most vehicle owners donot want their engine to use any oil between oilchanges even if they do not change it more often thanevery 7,500 miles (12,000 kilometers). Engineers

have improved machining operations and piston ringdesigns to help eliminate oil consumption.

Many stationary or industrial engines are not drivenon the road; therefore, they do not accumulate miles,yet they still may consume excessive oil.

A general rule for acceptable oil consumption is thatit should be about 0.002 to 0.004 pounds perhorsepower per hour.

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What Is Acceptable Oil Consumption?

Therefore, oil consumption is based on the

amount of work an engine performs. Although

the formula may not be usable for vehicle

engines used for daily transportation, it maybe usable by the marine or industrial engine

builder. Generally, oil consumption that is

greater than 1 quart for every 600 miles

(1,000 kilometers per liter) is considered to beexcessive with a motor vehicle.

SUMMARY

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SUMMARY

1. Normal engine oil pump pressure ranges from 10

to 60 PSI (200 to400 kPa) or 10 PSI for every1000 engine RPM.

2. Hydrodynamic oil pressure around engine

bearings is usually over 1,000 PSI (6,900 kPa).

3. The oil pump is driven directly by the crankshaft

or by a gear or shaft from the camshaft.

4. The last components to get oil from the oil pump

are the valve train parts.5. Some engines use an oil cooler.

REVIEW QUESTIONS

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By James D. HaldermanCopyright 2010, 2007, 2003 Pearson Education, Inc.,

Upper Saddle River, NJ 07458 All rights reserved. 37

REVIEW QUESTIONS

1. What causes a wedge-shaped film to form in the

oil?2. What is hydrodynamic lubrication?

3. Explain why internal engine leakage affects oil

pressure.

4. Describe how the oil flows from the oil pump,

through the filter and main engine bearings, to the

valve train.

5. What is the purpose of a windage tray?

CHAPTER QUIZ

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Automotive Engine Performance, 3/eBy James D. Halderman


CHAPTER QUIZ

1. Normal oil pump pressure in an engine is

________.a. 3 to 7 PSI

b. 10 to 60 PSI

c. 100 to 150 PSI

d. 180 to 210 PSI

CHAPTER QUIZ

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CHAPTER QUIZ

2. The oil pump pressure relief valve is also called

________.a. Oil pump valve

b. Pressure valve

c. Pressure regulating valve

d. Pressure dump valve

CHAPTER QUIZ

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CHAPTER QUIZ

3. A typical oil pump is what type of pump?

a. Positive displacementb. Centrifugal

c. Piston-type

d. Hydraulically driven

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CHAPTER QUIZ

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CHAPTER QUIZ

5. Technician A says that the oil pump draws

unfiltered oil from the bottom of the oil pan.Technician B says that the oil pump is driven from

the front of the crankshaft in some engines.

Which technician is correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

CHAPTER QUIZ

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CHAPTER QUIZ

6. Technician A says that oil pressure is affected by

the amount of main and rod bearing clearance.Technician B says that the oil pressure is lower

when the oil gets hot than when it is cold. Which

technician is correct?





CHAPTER QUIZ

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CHAPTER QUIZ

7. Technician A says that many engines use a

windage tray in the oil pan. Technician B saysthat some engines are equipped with an oil

cooler. Which technician is correct?





CHAPTER QUIZ

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CHAPTER QUIZ

8. The oil pressure warning light normally comes on

to warn the driver if the oil pressure drops below________.

a. 50 PSI

b. 30 PSI

c. 10 PSI

d. 3 to 7 PSI

CHAPTER QUIZ

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CHAPTER QUIZ

9. A typical oil pump can pump how many gallons

per minute?a. 3 to 6 gallons

b. 6 to 10 gallons

c. 10 to 60 gallons

d. 50 to 100 gallons

CHAPTER QUIZ

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CHAPTER QUIZ

10. In typical engine lubrication systems, what

components are the last to receive oil and the firstto suffer from a lack of oil or oil pressure?

a. Main bearings

b. Rod bearings

c. Valve train components

d. Oil filters

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