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 undamaged• Use liquid sealant or engine oil on threads• Install bolts in their proper holes• Run a nut over the bolt’s threads by hand• Clean bolt and cylinder block threads with a

thread chaser or tap• Tighten 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?


Gaskets

• 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 paper

• Silicone Gasket Material– Three different types

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

• Sealants– Usually 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 gaskets• Handle new gaskets carefully• Ensure clean mating surfaces

General Gasket Installation


General Gasket Installation

• Use the right gasket in the right position

• Only use sealants when specified

• Make sure all threads are clean and undamaged


• Head Gaskets– Seals combustion, coolant, and oil– Exposed to very low temperatures to combustion

temps of 2000 – 4000 °F– Seals vacuum and combustion pressures (1000 psi

peak pressures)– Allows for movement between head and block– Most late model engines use MLS gaskets

Specific Engine Gaskets


MLS Gasket


Common Head Gasket Failure

• Preignition/Detonation– 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


Adhesives

• Used only to hold a gasket in place• Do not assembly until adhesive is dry


• 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

Types of Sealants


Types of Sealants (Cont.)

• General Purpose Sealants– Available in liquid, brush on, or aerosol types– Ensure sealant is O2 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 parts• Three basic types– Fiber-packing– Two-piece lip– One-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 pivots

• Adjustable push rods• Rocker arms with

adjustable screws• Adjustable cam

followers• Selective 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 information

• Prime the oil pump prior to starting the engine• Follow 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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Chapter 13

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