Engine Overhaul

GENERAL INFORMATION

It is not always easy to decide whether a complete engine overhaul is necessary, since the decision must be based on a number of indicators.

High mileage is not a sufficient indication that an engine overhaul is required; on the other hand, low mileage does not rule out the need for an overhaul. The most important indicator is apparently the timeliness of routine engine maintenance. With timely oil and air filter replacement, and performance of all other necessary maintenance work, the engine will operate reliably for many thousands of kilometers. Conversely, insufficient or untimely maintenance may cause a sharp reduction in engine service life.

Increased oil consumption indicates wear of the piston rings, valve stem seals and/or valve guides. Make sure that leaks are not the cause of increased oil consumption, and only then conclude that the piston rings and valve guides are unserviceable. To determine the probable cause of the malfunction, measure the compression in the engine cylinders.

Check the oil pressure with a gauge installed in place of the oil pressure warning switch, and compare the result with the specified value. If the oil pressure is low, the cause may be wear of the main and connecting rod bearings and/or oil pump components.

Loss of power, hesitation, detonation or metallic knocking, increased noise from the valve train, and increased fuel consumption indicate the need for an engine overhaul, especially if all of these signs of abnormal operation occur at the same time. If all adjustments fail to improve engine operation, the only remedy is repair by replacing or reconditioning parts.

Major overhaul consists of restoring engine parts to the condition specified in the technical data for a new engine. During major overhaul, pistons and piston rings are replaced. Connecting rod and main bearing inserts are also replaced, and if necessary the crankshaft is ground undersize to restore the specified clearances between the main and connecting rod journals and the main and connecting rod bearings. As a rule, the valves are also reconditioned, since their condition at the time of overhaul is usually not fully satisfactory. During major engine overhaul, components such as the ignition distributor, starter and alternator are also repaired. As a result, the overhauled engine should have qualities close to those of a new unit and run a considerable distance without failure.

Warning: During major overhaul, important cooling system components such as hoses, thermostat and coolant pump must be replaced. The radiator must be carefully checked for leaks and for cleanliness of the internal passages. During engine major overhaul, the oil pump must also be replaced.

Before starting engine major overhaul, read the description of the relevant procedures to get a sense of the scope of work and its requirements. If all rules and procedures are followed, all necessary tools and fixtures are available, and all technical requirements are met, major overhaul is not difficult, but it requires considerable time. Allow at least two weeks, especially if parts must be repaired or reconditioned at a specialist workshop. Check the availability of spare parts and arrange in advance for the necessary special tools and equipment. Almost all work can be performed with a standard set of tools, although precision measuring instruments will be needed to check and determine the serviceability of certain parts. Checking the condition of parts is often carried out at specialist workshops, which also provide recommendations on replacing or reconditioning particular parts. Warning: Contact an auto service workshop only after the engine has been completely disassembled and the condition of all parts has been checked, especially the cylinder block and crankshaft, so that it can be decided which operations will be performed at the workshop. Since the condition of the cylinder block determines whether it should be repaired or a new or reconditioned block should be purchased, spare parts should be bought or machining of related parts should be carried out only after its condition has been thoroughly checked. As a rule, do not make hasty, unjustified decisions, otherwise repair may cost more due to installation of worn or reconditioned parts.

In conclusion, assemble all units with the utmost care in a clean area to prevent further failures of the rebuilt engine and to ensure its reliable operation.