2. High mileage does not always indicate the need for a major overhaul and, conversely, low mileage does not guarantee that no overhaul is needed. Probably the most important factor is the frequency of engine maintenance. An engine that has had frequent and regular oil and filter changes and all other maintenance procedures performed should provide long and reliable service. Conversely, an engine that has been neglected in its maintenance routine may require a major overhaul very quickly.
3. Very high oil consumption is an indication of problems with the piston rings, valve stem seals and/or valve guides. However, before you decide to replace the pistons and valve stem seals, check whether the excessive oil consumption is not the result of simple leaks. To determine the real cause, perform a compression test as described in Chapters 2A and 26 (depending on the engine type).
4. Check the oil pressure with a pressure gauge installed in place of the oil pressure sensor and compare the obtained pressure value with the Technical Data. If the pressure is low, most likely the main and connecting rod bearings and / or the oil pump gears are worn.
5. Loss of power, rough running, knocking or metallic noises in the engine, increased noise in the valve train and high fuel consumption may also indicate a need for a major overhaul, especially if these symptoms occur simultaneously. If a full service does not correct the situation, the only solution is an engine overhaul.
6. Overhaul of the engine involves restoring all internal parts to the technical characteristics of a new engine. During overhaul, the cylinders are bored, pistons and piston rings are replaced. As a rule, new main and connecting rod bearings are installed; if necessary, the crankshaft can be machined to restore the journals. Attention is also paid to the valves, since they are not in the best condition at the time of repair. If the engine is disassembled, other components such as the distributor, starter and generator can also be disassembled and repaired. The end result of the repair should be a "like new" engine that will serve without problems for many thousands of kilometers.
7. During a major overhaul, important cooling system components such as hoses, thermostat, and water pump should be replaced. It would be a good idea to add the oil pump to this list as well. The radiator should be thoroughly checked to make sure it is not leaking or clogged.
8. Before you begin rebuilding your engine, read the entire repair procedure to familiarize yourself with the requirements and scope of work. Rebuilding an engine is not a difficult job if you follow all the instructions carefully, have the necessary tools and equipment, and meet all the technical requirements. However, the repair is a very labor-intensive operation. Plan for it to take at least two weeks, especially if rebuilding work is required. Check the availability of spare parts for the engine and make sure you have or can borrow all the necessary tools and equipment. Most work can be done using general-purpose hand tools, but you will need some high-precision measuring instruments to inspect the parts. Service stations and repair shops can competently take measurements and give you advice on repairs and rebuilding parts.
9. In order to make the right decision about the necessary work to restore parts (especially the cylinder block/crankcase or crankshaft), disassemble the engine completely and check all the parts. The condition of these parts is the determining factor when deciding whether to assemble the engine from "native" parts or buy reconditioned units. Therefore, do not purchase or install parts until you have thoroughly checked them.
The basic rule is that the cost of repairs is determined by the time spent on it, so you should not install worn out or non-standard parts.
10. As a final note, we would like to remind you that a long life of a reconditioned engine with minimal care is ensured by careful assembly in a sterile environment.