Engine Overhaul

GENERAL INFORMATION

It is not always easy to decide whether a complete engine overhaul is advisable, since a number of objective indicators must be taken into account.

High mileage is not in itself a sufficient indicator 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 most likely the timeliness of routine engine maintenance. With timely oil and filter changes, and with all other required maintenance performed, the engine will serve 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 guides and oil seal caps. 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 (see subsection 3.1.1.2).

To determine the scope of the work, check the compression in the engine cylinders. Also perform a vacuum gauge test and determine the nature of the readings of this instrument (see subsection 3.1.2.3).

Check the oil pressure with a gauge screwed into the oil pressure sensor port 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 or of the oil pump components.

Loss of power, misfiring, detonation or metallic knocking, increased noise from the valve train, and increased fuel consumption indicate the need for an engine overhaul, especially if all these signs of abnormal operation appear at the same time. If performing all adjustments does not improve operation, the only remedy for abnormal engine operation is an engine overhaul. An engine overhaul consists of restoring engine components to the condition specified in the technical data for a new engine. During an engine overhaul, pistons and piston rings are replaced, and cylinders are bored or honed. After cylinder repair, which is performed at a specialized workshop, installation of oversize pistons is required. Connecting rod and main bearing shells of the crankshaft, as well as the camshaft bearing cap bearings, are also subject to replacement; if necessary, the crankshaft journals should be ground to restore normal clearances with the connecting rod and main bearing shells. As a rule, the valves are also subject to repair, since their condition at the time of overhaul is usually not entirely satisfactory. During an engine overhaul, components such as the starter, alternator and ignition distributor are also repaired. As a result, the rebuilt engine should have the qualities of a new unit and withstand considerable mileage without failures.

Warning During an engine overhaul, important cooling system components such as hoses, drive belts, thermostat and coolant pump must be replaced. The radiator must be checked for leaks and for cleanliness of the internal passages (see subsection 4.3). If you have purchased a remanufactured engine or an incomplete short block, some suppliers do not warrant the operation of these units unless the radiator has been thoroughly flushed. During an engine overhaul, it is also recommended to replace the oil pump.

Before starting an engine overhaul, read the description of the relevant procedures to get an understanding of the scope of work and its requirements. If all standards and procedures are followed, and all necessary tools and equipment are available, the overhaul is not difficult, but it requires a significant amount of time. Allow at least two weeks, especially if parts must be repaired or restored at a specialized workshop. Check the availability of spare parts and obtain the necessary special tools and equipment in advance. Almost all work can be performed with a standard set of tools, although precision measuring instruments will be required to inspect and determine the serviceability of certain parts. Parts condition is often checked at specialized workshops, which also provide recommendations on replacing or restoring particular parts.

Warning Contact an automotive repair shop only after the engine has been completely disassembled and the condition of all components has been inspected, especially the cylinder block, in order to determine which maintenance and repair operations will be performed at the shop.

Since the condition of the cylinder block is the determining factor in deciding whether to repair it or purchase a new (or remanufactured) cylinder block, spare parts should be purchased or machining operations on related components should be performed only after a thorough inspection of its technical condition. Keep in mind that the true cost of a repair is time; this way you will not have to pay for installing 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.