You will find a wide range of information here - from tips for preparing for repairs and acquiring new components and parts, to step-by-step removal and installation procedures.
The following paragraphs are designed to help you determine if your engine needs an overhaul. Describes how to remove and install the engine if it needs repair. For information on repairing the engine without removing it from the vehicle, refer to the relevant paragraphs in parts A and B chapter 2.
The technical data included in this chapter is of a general nature and contains information only for checking oil pressure and compression and some tightening torques (related to the bottom of the engine). For additional technical data, please refer to chapters 2A or 2B.
It is not always easy to determine when an engine needs an overhaul. It depends on many factors.
A high mileage does not necessarily indicate the need for a major overhaul. At the same time, low mileage does not at all exclude the fact that the engine requires a major overhaul. The most important factor can be considered the regularity of service. An engine that has been regularly and frequently changed oil and filter, which has been regularly and other required maintenance, can reliably and for a long time without major repairs and provide many thousands of kilometers. Conversely, an engine that has been neglected may require an overhaul very early, regardless of its age.
Excessive oil consumption is a sign that piston rings, riveted seals and/or valve guides need attention. Before deciding that the rings and/or guide bushings are worn, make sure that the cause is not an oil leak. To determine the amount of work required, perform a compression test (see paragraph 3). Also check vacuum readings under various conditions (see paragraph 4).
Check the oil pressure with a pressure gauge installed in place of the oil pressure sensor and compare the reading with the prescribed value (see paragraph 2). If the pressure is very low, the cause may be worn crankshaft bearings and/or oil pump.
Loss of power, rough running, knocking or metallic noises from the engine, increased valvetrain noise, and high fuel consumption can also indicate the need for an overhaul, especially if they all occur at the same time. If full service does not solve the problem, the only solution is a major overhaul.
Overhaul of the engine involves the restoration of all internal elements in accordance with the technical parameters of the new engine. During a major overhaul, piston rings are replaced and cylinders are restored (by boring and/or honing) (pic. 1.2 and 1.3). In case of boring of cylinders installation of new pistons of the repair size is required. As a rule, new crankshaft main and connecting rod bearings are installed, as well as camshaft bearings. If necessary, the crankshaft itself can be reground to restore the necks (pic. 1.4). As a rule, valves are also subject to repair, since at the time of repair their condition is usually far from ideal. When an engine overhaul is performed, other components such as the distributor, starter and alternator can be repaired. The result of the work should be an engine that, in terms of its characteristics, is not inferior to a new one, which will provide you with thousands and thousands of kilometers of trouble-free mileage.
Pic. 1.2. Cylinder block bore. At a specialized service station, parking equipment is used to restore cylinders
Pic. 1.3. Cylinder bores are usually followed by honing
Pic. 1.4. Regrinding of the crankshaft journal
Application. Key components of the cooling system such as hoses, drive belts, thermostat, and water pump should also be replaced when the engine is overhauled. The radiator should be carefully checked for blockage or leakage (see chapter 3). When purchasing a remanufactured engine or an incomplete cylinder block, some repair organizations do not guarantee that their engines will not operate unless the radiator is professionally flushed. In addition, it is not recommended to restore the oil pump when performing a major overhaul. It is recommended to replace it.
Overhauling the internal components of modern engines is a difficult and time-consuming job that requires the use of a significant number of special tools and fixtures. Therefore, it is recommended to entrust this matter to professionals (pic. 1.5, 1.6 and 1.7). A competent engine repair specialist will perform a competent inspection of old components and parts and make recommendations for repair or replacement of the engine. Never purchase parts or machine removed parts until the engine block has been thoroughly inspected by a specialized service station. Typically, the main cost of a major overhaul is the time spent, especially since the vehicle can be out of service for at least two weeks or more. Please be aware that some repair organizations may only overhaul the engine after the «old» engine, while others have large stocks of already remanufactured engines that are not being exchanged. Many engine repair shops, depending on their workload, can take up to two weeks to fully restore an engine. Sometimes, to save time, it makes more sense to simply replace the engine with another, already rebuilt unit.
Pic. 1.5. Checking the connecting rod for deformation using special equipment
Pic. 1.6. Using a Bore Gauge to Check the Main Bearing Bore Diameter
Pic. 1.7. Uneven piston wear like shown is a sign of connecting rod deformation