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Chapter 13

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.).

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Chapter 13

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  1. Chapter 13 Engine Sealing and Reassembly

  2. 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

  3. 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

  4. Tightening Sequence Examples

  5. Bolt Installation Tips • 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

  6. Thread Cleaning

  7. Thread Repair • Overtorquing or incorrect threading will strip threads • May be repaired using thread insert or Helicoil

  8. 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

  9. TTY Bolts (Cont.)

  10. Knowledge Check • Why is proper tightening of bolts necessary when installing engine components?

  11. 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

  12. Gasket Classifications • 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

  13. Cut Gaskets • Paper/Fiber Gaskets – low temperature/low pressure • Cork Gaskets – not commonly used today

  14. 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

  15. 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

  16. General Gasket Installation • Never reuse old gaskets • Handle new gaskets carefully • Ensure clean mating surfaces

  17. General Gasket Installation • Use the right gasket in the right position • Only use sealants when specified • Make sure all threads are clean and undamaged

  18. Specific Engine Gaskets • 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

  19. MLS Gasket

  20. 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

  21. 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

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

  23. 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

  24. 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

  25. 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

  26. Applying RTV

  27. Antiseize Compounds • Prevents dissimilar metals from reacting with each other and seizing • Commonly used on aluminum parts • Always follow manufacturer recommendations when using

  28. 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?

  29. Engine Gaskets and Seals

  30. Oil Seals • Used with rotating parts • Three basic types • Fiber-packing • Two-piece lip • One-piece radial

  31. Oil Seals (Cont.)

  32. Two-Piece Lip Seal

  33. 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

  34. Timing Belts and Chains • Cam and crank alignment is critical • Follow timing procedures exactly • Ensure the tensioners apply properly

  35. Methods of ValveLash Adjustment • Rocker arms with adjustable pivots • Adjustable push rods • Rocker arms with adjustable screws • Adjustable cam followers • Selective shims

  36. 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

  37. 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

  38. Knowledge Check • What are two methods of adjusting valve lash?

  39. Engine Installation Tips • 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

  40. 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

  41. 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

  42. 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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