Automotive Bearings and Sealants
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Transcript of Automotive Bearings and Sealants
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.