General

This Part of the Chapter contains procedures for engine removal and installation, as well as general overhaul of the cylinder head and internal engine components.

The material presented here includes a wide range of information, from practical advice on purchasing the necessary parts to detailed step-by-step instructions for removal, inspection, reconditioning and installation of internal engine components.

The procedures are written on the assumption that the engine has been completely removed from the vehicle and mounted on an engine stand or a sturdy workbench. All information concerning engine repair procedures that can be performed without removing the engine from the vehicle (in situ) is given in the 4-Cylinder Engines and V6 Engines Parts of this Chapter.

It is not always easy to determine when an engine overhaul is required. A number of different factors must be taken into account.

High mileage is not necessarily an indication that the engine needs an overhaul. On the other hand, low mileage is not a sufficient guarantee of good engine condition. The main factor determining engine service life is the frequency and regularity with which routine and general maintenance is performed. With normal care, the engine will reliably serve for many thousands of kilometers, whereas negligent maintenance combined with careless driving may necessitate an engine overhaul after a very short period.

Excessive oil consumption may indicate the need to inspect the piston rings, valve stem seals and/or valve guides. First of all, make sure that the oil loss is not caused by external leaks. Consult a qualified specialist who can determine the general condition of your vehicle's engine based on the results of a cylinder compression test (see Cylinder Compression Test Section) and vacuum gauge readings under various operating conditions (see Engine Diagnosis Using a Vacuum Gauge Section).

Loss of power, unstable idle speed, excessive valve train noise and increased fuel consumption are usually characteristic signs that an engine overhaul is required, especially when all of these symptoms occur simultaneously. If performing the full range of adjustments does not solve the problems, the only remedy will be a complete mechanical overhaul of the engine.

An engine overhaul means restoring all of the engine's operating parameters to the level of a new engine. During an overhaul, the piston rings must always be replaced and the cylinder bores must be reconditioned (boring and/or honing). If the cylinders are bored, pistons of the appropriate oversize must be selected. Generally, the main and connecting rod bearings are replaced and, if necessary, the crankshaft journals may be ground and reconditioned. The valves must always be serviced, since their condition at the time an engine overhaul becomes necessary is almost certainly poor. Ancillary components such as the ignition distributor, starter and alternator are usually reconditioned at the same time as the general engine overhaul. As a result of the overhaul, engine parameters are restored to new-engine values, and the engine will then run reliably for many thousands of kilometers.

Critical cooling system components such as hoses, drive belts, thermostat and water pump MUST be replaced with new parts during an engine overhaul. In addition, carefully inspect the radiator (see the Cooling, Heating and Ventilation Chapter). If signs of leaks or reduced flow are found, the radiator must also be replaced. Many dealerships and service shops will not guarantee a rebuilt engine unless the radiator has been professionally cleaned and repaired. Do not forget to also check the condition of the oil pump (see the relevant Sections of this Chapter).

Before starting an engine overhaul, study the material in this Part carefully to prepare yourself theoretically for the work ahead. Note that an engine overhaul does not require a high level of professional skill, but it takes a considerable amount of time. Plan to be without the vehicle for at least two weeks, especially if you need to take it to a machine shop for certain reconditioning work. Shop around to check the availability of parts, tools and equipment. Prepare all necessary materials in advance. Most of the work can be carried out with a standard set of hand tools, but some of the checks to determine whether individual components are suitable for further use require precision measuring equipment. In doubtful situations, consult the specialists at a service shop, who can always help you decide whether a given internal engine component should be replaced or reconditioned.

Before taking any parts to a machine shop for reconditioning, completely disassemble the engine and all of its internal components. Remember that the condition of the engine block is the decisive factor in whether an engine overhaul is worthwhile. It is often cheaper and more reliable to replace a worn engine with a reconditioned one. Never purchase replacement components until you have thoroughly inspected the block. Remember that time is the main cost factor in an engine overhaul, so do not waste it installing worn or non-standard assemblies and components.

In conclusion, all efforts to recondition worn components will be wasted if cleanliness is not strictly observed during assembly.