2. This section contains information ranging from tips on preparing for repairs and selecting spare parts to detailed, step-by-step descriptions of procedures for removing, checking, restoring and installing internal engine components
3. After paragraph 5, all information assumes a situation where the engine has already been removed from the vehicle. For information assuming repair of the engine while it is still in the vehicle, as well as operations for removing and repairing external engine components that do not require engine removal, refer to the previous relevant parts of this chapter (2A - for gasoline engines and 2B - for diesel) and to paragraph 5 of this chapter. Many of the operations that make up the repair procedures for engine components that are not removed from the vehicle can be skipped if the engine has already been removed.
4. In addition to the tightening torques for threaded connections given at the beginning of the relevant chapters 2A or 2B, specifications regarding engine repair are given at the beginning of this chapters 2B.
1. It is not always easy to decide when and whether an engine needs a major overhaul, since many factors need to be taken into account.
2. High mileage does not mean that a major engine overhaul is necessary, just as low mileage does not guarantee good engine condition. The main and most important thing in this is the regularity of maintenance. An engine in which oil and filters were changed frequently and regularly and other necessary operations were carried out in a timely manner will respond to care with long and reliable operation.
3. Increased oil consumption indicates that the piston rings, valve stem seals and/or valve guides require attention. Before deciding on the cause of increased oil consumption, make sure that oil leaks are not the culprit. To get an idea of the possible cause of the problem, check the compression as described in Chapter 2A or 2B.
4. Check the oil pressure using a compression gauge screwed in place of the emergency oil pressure sensor and compare with the values specified Specifications. If it is too low, the main or connecting rod bearings or the oil pump may be worn out.
5. Loss of power, rough running, knocking or metallic engine noise, increased valve timing noise and increased fuel consumption may indicate the need for repair, especially if several symptoms are present at the same time. If a full service does not help to eliminate the situation, the only solution is "surgery".
6. Engine overhaul involves restoring engine components to new engine specifications. During the overhaul, pistons and piston rings are replaced, and new connecting rod and main bearings are usually installed; if necessary, the crankshaft is ground to restore the journals. The valve mechanism is inspected, since they are usually not in the best condition in this situation. It would be a good idea to also overhaul the engine's attachments, such as the starter and generator. The end result should be a virtually new engine that will run for hundreds of thousands of kilometers without any problems.
Note. During a major overhaul, the least durable and critical parts and units of the cooling system, such as hoses, thermostat and water pump, should also be replaced. Carefully check the radiator for leaks and clogged metal with corrosion products. It would be a good idea to also replace the oil pump during a major overhaul of the engine.
7. Before you begin rebuilding an engine, familiarize yourself with the basic procedures to get an idea of the scope and complexity of the work ahead. Rebuilding an engine is not difficult if you follow all the instructions carefully, have the necessary tools and equipment, and carefully follow the requirements of the Specifications. Of course, it will take a lot of time. Plan to be without the car for at least a couple of weeks, especially if you need to take parts to a workshop for rebuilding. Check that you have the necessary spare parts and the necessary tools and equipment, which you should stock up on in advance. Most of the work can be done with ordinary tools, although in some cases you may need a precision measuring tool to decide whether to replace parts. Often, in workshops, specialists can advise, by taking measurements, whether it is worth rebuilding the removed parts, or whether it is better to replace them with new ones.
Note: Wait until the engine is completely disassembled before deciding to rebuild or replace parts (this is especially true for the crankshaft and cylinder block) and performing the necessary measurements. Their condition should be the main factor in deciding whether to restore the engine or simply buy a restored one. Therefore, do not purchase spare parts in advance and do not start repairing other engine systems. until you make such a decision. General rule: the main cost of repair is time, so you should not install non-standard or old parts in the engine. Since repairs are expensive and time-consuming, you should not install worn or non-standard parts.
8. And the last note: to get the desired result - maximum life with minimum problems from a rebuilt engine - assemble the engine carefully, with clean tools on clean equipment.
This publication is borrowed from the resource audimanual.ru