Engine Sealing and Reassembly 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’d) 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.

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.

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.

Gaskets Used to provide a positive seal between bolted together parts. Also act as spacers, wear insulators, and vibration dampers. Gaskets are used on stationary parts. Seals are used with moving parts.

General Gasket Installation Never reuse old gaskets. Handle new gaskets carefully. Ensure clean mating surfaces. Use the right gasket in the right position. Only use sealants when specified. Make sure all threads are clean and undamaged.

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

Types of Sealants Aerobic Sealants Anaerobic 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 (cont’d) 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’d) 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

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

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

Oil Seals (Cont’d)

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 Valve Lash Adjustment Rocker arms with adjustable pivots Adjustable push rods Rocker arms with adjustable screws Adjustable cam followers Selective shims

Adjusting Valve Lash

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.

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.