Recommendations are also provided regarding all stages of repair, from preparing equipment and purchasing tools and spare parts to a detailed step-by-step description of the procedures for removing, inspecting, repairing and installing engine components.
When describing the procedures in the following subsections, it is assumed that the engine has previously been removed from the vehicle. Removal, inspection, repair and installation of engine elements installed in a car are described in Part A this chapter.
This part of the chapter provides the specifications necessary to check the oil pressure and measure the compression. For additional technical data and tightening torque values, please contact Part A this chapter.
Sometimes it is not easy to determine the feasibility of a major renovation.
The fact that high mileage is not always an indicator of the need for major repairs, and low mileage is not a reason not to carry out repairs, is probably the main factor that requires consideration. An engine that has had its oil and filter regularly changed and other necessary maintenance performed should operate reliably for many thousands of kilometers. A poorly maintained engine, on the other hand, may require major repairs with very low mileage.
Excessive oil consumption indicates that the piston rings, valve seals and/or guides require inspection. Make sure that oil leakage through gaskets and seals does not cause you to mistakenly believe that the rings and/or guides are worn out. To determine the likely cause of the problem, perform a compression test (see subsection 3) or check the tightness of the cylinders (see subsection 4).
Check the oil pressure by connecting a pressure gauge to the oil pressure sensor hole and compare it with the value given in the specifications in this chapter (see subsection 2). If the pressure is extremely low, the engine bearings and/or oil pump are likely worn out.
Reduced power, unstable engine operation, knocking and metallic grinding noises, excessive valve train noise and high fuel consumption also indicate the need for a major overhaul, especially if these factors occur simultaneously. If problems are not resolved during maintenance, then major repairs are inevitable.
A major overhaul includes the restoration of all internal elements until the engine acquires the parameters of a new power unit. During a major overhaul, the piston rings are replaced, as well as the engine cylinders are bored to repair sizes (boring and honing) (see illustrations 1.2 and 1.3).
1.2. A mechanic is boring engine cylinders on a special machine
1.3. After boring, the cylinders are honed using a special installation
If boring is done in a car repair shop, then new repair-size pistons are installed on the engine. The main bearings and bearings of the lower head of the connecting rod are also replaced, and if necessary, the crankshaft is ground to restore its journals (see illustration 1.4).
1.4. Machining of crankshaft main bearing journals
During engine repairs, valves are also restored, since at this stage their condition usually leaves much to be desired. If necessary, also repair or replace the alternator and starter. As a result of the repair, the engine should acquire the characteristics of a new engine, capable of operating without failure for many kilometers.
Note: Critical cooling system components such as hoses, drive belt, thermostat, and pump should be replaced when a major overhaul is performed. The radiator should be checked for leaks and blockages (see chapter 3). Some shops will not provide a warranty on a replacement rebuilt engine or power unit assembled from a replacement truncated cylinder block unless the cooling system radiator has been replaced or professionally cleaned. In addition, when carrying out a major overhaul, it is recommended not to repair but to replace the oil pump.
Restoring the internal elements of a modern engine is a rather labor-intensive procedure that requires special skills and patience, as well as the use of many special devices. It is preferable to entrust this type of work to specialists from a service station (see illustrations 1.5, 1.6 and 1.7). Before deciding on the type of service and the list of repair operations, wait until the engine is removed and all its elements are inspected (especially the cylinder block). The condition of major parts is critical when deciding whether to rebuild an old engine or purchase a new or remanufactured powertrain, so do not purchase parts or repair other components until the cylinder block has been inspected. As a rule, the main cost of repairs is a waste of time, so you should not install worn or non-standard parts.
1.5. A mechanic determines the bending of a connecting rod using special equipment
1.6. The diameter of the main bearing bore is determined using a bore gauge
1.7. Uneven piston wear indicates that the connecting rod is bent
It should be noted that engine restoration at service stations, as a rule, lasts at least two weeks. At some stations, you can only restore the existing engine, while at others, in addition, you can install a repaired engine to replace the removed one. Perhaps such a decision will be economically justified.