Automotive Bearings and Sealants

Objectives

Explain purpose of bearings Identify different types, construction, and

uses of automotive bearings List types of lubricant used in a light vehicle Explain different types, construction, and

uses of gaskets

Objectives

Explain types and uses of chemical automotive sealants

Explain different types, construction, and uses of seals

Objectives

Explain the purpose of the various gaskets used to seal an engine.

Identify the major gasket types and their uses. Explain general gasket installation procedures. Describe the methods used to seal the timing

cover and rear main bearing.

Bearings and Bushings

Bearings are used when two components move against or with each other

Bearing Loads– Usually computed by weight and movement of

load

Bearings and Bushings

Bearing Loads– Weight determines size, placement, and type of

bearing to be used– Thrust load looks at direction and amount of force

against the weight

Bearings and Bushings

Bearing Journals and Races– Machined areas on a shaft– Provide a smooth finish to protect bearing– Usually hardened to withstand loads

Bearings and Bushings

Races– Serve same purpose as the journal– Normally included with replacement bearing– Assembled as part of bearing or can be loose

Bearings and Bushings

Bearing Inserts– Also known as “plain bearings”– Used in engine as rod or main bearings– Fitted into a mounting component– Two pieces are needed to make one complete

bearing

Bearings and Bushings

Roller Bearings– Support radial loads and small amount of thrust– Typical roller bearing is fairly small and has

several rollers trapped in a cage

Bearings and Bushings

Roller Bearings– Cage holds bearings in a circle and maintains

equal spacing– Straight or tapered– Needle bearings are also roller bearings

May or may not be held in a cage

Bearings and Bushings

Ball Bearings– Similar to a roller bearing– Highly machined steel balls versus rollers– Support axial and radial loads well– Sometimes two rows of balls are present to

improve load support

Bearings and Bushings

Bushings– Thin steel tubing cut to specific lengths– Coated with copper– Does not support axial loads– Limits radial movement of a shaft– Cannot be used in high-thrust or high-radial load

areas

Inspecting and Repacking a Wheel Bearing

Bearing failure is indicated by a noise from bearing area

Bearing failure causes two types of damage– Spalling– Brinelling

Inspecting and Repacking a Wheel Bearing

Dry bearings can weld themselves to the race or the component

Inspecting and Repacking a Wheel Bearing

Remove suspected bearing and clean it thoroughly

Dry bearing with compressed air Do not allow rollers or cage to spin

Inspecting and Repacking a Wheel Bearing

Inspect each ball or roller for damage Inspect case and race for damage Any sign of damage warrants replacing

bearing

Inspecting and Repacking a Wheel Bearing

Repacking the Bearing– Each roller or ball must be greased before

installation– Several types of repacking tools are available

including compressed-air-powered

Inspecting and Repacking a Wheel Bearing

Repacking the Bearing– Bearing must be clean and dry before

repacking– Ensure grease extends up through bearing

when complete

Lubricants

Grease is used on roller and ball bearing components

Grease must be matched to component and its usage

Grease can be multipurpose Always consult service manual

Bearing Construction (Friction reducers)

Friction Bearing- Two smooth surfaces sliding against each other

Antifriction bearing- utilizes balls or rollers between moving parts

Antifriction bearings

Bearing Clearances

Bearings must be tight enough to resist pounding but lose enough for oil to enter

.002” .05mm

Oil Seals

Oil is retained in the engine from Gaskets- cork or rubber Sealants-RTV-Room temperature vulcanizing Oil seals

Gasket Classifications

Hard gaskets – Made of steel, copper, or a composite of metal and fiber

Soft gaskets – Made of cork, rubber, or paper

Silicone gasket material– Three different types

Sealants– Usually in liquid form

Gaskets

Common Engine Gaskets

Head gaskets– Have the most demanding job.

Manifold gaskets– Are intake, exhaust, or combination.

Valve cover gaskets– Must seal between different metals or materials.

Oil pan gaskets– Seal between the block and pan.

Engine Gaskets and Seals

Gaskets

Retain lubricants or to seal a chamber Head Gasket

– Seals extremely high pressure of the combustion chamber

– Most head gaskets are a composite material– Verify correct part for application

Gaskets

Intake and Exhaust – Must be designed to work in extreme heat– Must be able to work between two different

metals

Gaskets

Other Gaskets– Made from cork, synthetic rubber, neoprene,

paper, and chemical-based– Use the right gasket for the job at hand

Types of Sealants

Aerobic sealants– Cure only when exposed to oxygen (air).– Are commonly used to form gaskets.

Anaerobic sealants– Cure only in the absence of oxygen (air).– Are used for thread sealant.

Chemical Sealants

Chemical sealers– Gasket sealer– Room temperature vulcanizing (RTV) sealer

RTV cannot be used in high heat and high pressure applications

Chemical Sealants

Cannot be used on fuel system components

RTV color denotes application and temperature ranges

Seals

Used between moving components and their housings to retain liquids

Withstand high pressure and high temperatures

Lip seals are most common type – Some have garter spring to hold seal tight to

surface

Seals

O-rings– Rubber ring fits into a groove on moving or

stationary component– Extends beyond groove and pressed against

second component

Seals

Boots– Used primarily to protect rather than seal– Most common is CV joint boot

Oil Seal Designs

Fiber-packing type Two-piece lip type One-piece radial type

Oil Seal Designs (Cont’d)

Sealants

Oil Seals

Summary

Sealants include gaskets, chemicals, or seals Bearings must support axial and radial loads Gaskets used between stationary parts Seals used between moving parts O-rings are special purpose seals

Summary

Gaskets serve as sealers, spacers, wear indicators, and vibration dampers.

General recommendations for installing gaskets include the following: – Never reuse old ones.– Clean all mating surfaces.– Use sealants properly.

Summary (Cont’d)

Head gaskets on today’s bi-metal engines have a demanding job.

General-purpose sealers aid in gasket sealing without upsetting the performance of the gasket.

Oil seals keep oil and other fluids from escaping around a rotating shaft.