Chapter 13

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Chapter 13

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Chapter 13

Engine Sealing and Reassembly


Torque Principles

All metals are elastic

Bolts can stretch and compress

Stretch applies clamping force

Too much stretch destroys the bolt

Bolts torqued to yield never return to normal



Torque Principles (Cont.)

Most torque values are for dry fasteners

Lubricants increase applied torque

Visually inspect the bolts

Use lubricants or sealers as specified

Tighten in the correct sequence

Ensure proper fastener is used


Tightening Sequence Examples


Threads must be clean and undamagedUse liquid sealant or engine oil on threadsInstall bolts in their proper holesRun a nut over the bolt’s threads by handClean bolt and cylinder block threads with a thread chaser or tapTighten bolts to the proper torque specification

Bolt Installation Tips


Thread Cleaning


Thread Repair

Overtorquing or incorrect threading will strip threads

May be repaired using thread insert or Helicoil


Torque-To-Yield Bolts

TTY fasteners are designed to stretch when properly tightened

Once at yield point the bolt is permanently stretched

Commonly used as cylinder head bolts

Torqued in steps


TTY Bolts (Cont.)


Knowledge Check

Why is proper tightening of bolts necessary when installing engine components?



Used to provide a positive seal between parts bolted together

Also act as spacers, wear insulators, and vibration dampers

Gaskets are used on stationary parts

Seals are used with moving parts


Cut or Soft Gaskets Made of cork, rubber, or paperSilicone Gasket MaterialThree different typesHard Gaskets Made of steel, copper, or a composite of metal and fiberSealantsUsually in liquid form

Gasket Classifications


Paper/Fiber Gaskets – low temperature/low pressure Cork Gaskets – not commonly used today

Cut Gaskets


Other Gaskets

Molded Rubber Gaskets – retain flexibility and are durable

May have steel insert around bolt holes

Do not use sealants or adhesives

Hard Gaskets – made from steel and other materials

Used as cylinder head and exhaust manifold gaskets



Replacement Gaskets

Available individually or as sets

A full set contains all gaskets necessary for rebuilding an engine

Some components are assembled using form in place gaskets

Check TSBs for updated gaskets


Never reuse old gasketsHandle new gaskets carefullyEnsure clean mating surfaces

General Gasket Installation


General Gasket Installation

Use the right gasket in the right positionOnly use sealants when specifiedMake sure all threads are clean and undamaged


Head GasketsSeals combustion, coolant, and oilExposed to very low temperatures to combustion temps of 2000 – 4000 °FSeals vacuum and combustion pressures (1000 psi peak pressures)Allows for movement between head and blockMost late model engines use MLS gaskets

Specific Engine Gaskets


MLS Gasket


Common Head Gasket Failure


Incorrect timing or mixture, vacuum leak, faulty cooling system

Engine Overheating

Improper Installation

Wrong head or block surface finish, incorrect bolt tightening, stretched bolts, improper sealant use, incorrect gasket



Specific Engine Gaskets (Cont.)

Manifold Gaskets

Intake, exhaust, or combination

Valve Cover Gaskets

Must seal between different metals or materials

Oil Pan Gaskets

Seal between the block and pan

EGR Valve

Gasket may be used to regulate exhaust flow



Used only to hold a gasket in placeDo not assembly until adhesive is dry


Aerobic SealantsCure only when exposed to oxygen (air)Are commonly used to form gasketsAnaerobic SealantsCure only in the absence of oxygen (air)Are used for thread sealant

Types of Sealants


Types of Sealants (Cont.)

General Purpose Sealants

Available in liquid, brush on, or aerosol types

Ensure sealant is O


sensor safe

Never use a hard drying sealant on gaskets

Thread Sealants

Used on bolts passing through a liquid passage


Types of Sealants (Cont.)

Silicone Sealants

Formed-in-place gasket

Applied to mating surfaces

Room Temperature Vulcanizing (RTV) most common

Too much RTV can be squeezed out and into oil system


Applying RTV


Antiseize Compounds

Prevents dissimilar metals from reacting with each other and seizing

Commonly used on aluminum parts

Always follow manufacturer recommendations when using


Knowledge Check

Technician A says gaskets are used between moving parts of the engine. Technician B says liquid RTV gasket maker can be used in place of any engine gasket. Who is correct?


Engine Gaskets and Seals


Used with rotating partsThree basic typesFiber-packingTwo-piece lipOne-piece radial

Oil Seals


Oil Seals (Cont.)


Two-Piece Lip Seal


Engine Reassembly

Clean and lubricate head bolts

Match head gasket to block

Place head on block and alignment dowels

Torque head bolts in sequence

Lube pushrods and rocker arms


Timing Belts and Chains

Cam and crank alignment is critical

Follow timing procedures exactly

Ensure the tensioners apply properly


Methods of ValveLash Adjustment

Rocker arms with adjustable pivotsAdjustable push rodsRocker arms with adjustable screwsAdjustable cam followersSelective shims


Final Assembly Steps

Install various covers, pulleys, and sensors

Ensure coolant drain plugs are installed

Coat sensor O-rings with oil before installing

Install vibration damper onto crankshaft

Make sure manifold mating surfaces are clean and install manifolds


Final Assembly Steps (Cont.)

Install the thermostat and housing

Install the flexplate and torque converter or the flywheel and clutch components

Inspect and loosely install motor mounts

Install all other related components as necessary


Knowledge Check

What are two methods of adjusting valve lash?


Always refer to the manufacturer’s service informationPrime the oil pump prior to starting the engineFollow the manufacturer’s computer relearn procedures if applicable

Engine Installation Tips


Starting Procedure

Set ignition timing as closely as possible

Fill fuel tank with several gallons of fresh fuel

Start engine and run at 1500 RPM

Run until engine reaches normal operating temperature then shut off

Recheck all adjustments


Break-In Procedure

Test drive at 30 MPH and accelerate to 50 MPH at full throttle

Repeat at least 10 times

Apply loads to engine for short periods

This helps assure the rings seat


Relearn Procedures

The computer will need to learn the engine condition and make adjustments

Idle and transmission shift schedules will relearn

Reset any memory functions such as the clock and radio presets








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