Significant mileage is not necessarily a sign that the engine needs a major overhaul. On the other hand, a short period of operation also cannot be considered a sufficient guarantee of the good condition of the power unit. Perhaps the main factor determining the life of the engine is the frequency and regularity of performing general and routine maintenance of the car. With normal care, the engine will reliably serve for many, many thousands of kilometers, while a careless attitude to the implementation of routine maintenance procedures, coupled with a careless driving style, can lead to the need for a major overhaul of the power unit after a very short time.
Excessive engine oil consumption can be considered a signal to check the condition of the piston rings, valve stem seals and / or valve guides. Naturally, first of all, you should make sure that oil losses are not associated with the development of its external leaks. Seek help from a qualified technician who can help you determine the overall condition of your vehicle's engine based on the results of a cylinder compression test and vacuum depth measurements at various initial settings.
Loss of developed power, violation of speed stability, excessive noise background of the valve mechanism, increased fuel consumption are usually quite characteristic signs of the need for an engine overhaul, especially when all these factors appear simultaneously. If performing a full range of adjustments does not resolve the issue, the only recourse is to perform a general mechanical rebuild on the engine.
The overhaul of the power unit involves the restoration of all its operating parameters to the level characteristic of the new engine. During the overhaul, it is mandatory to replace the piston rings and restore the cylinder mirrors (turning and/or honing). In the case of cylinder turning, pistons of the appropriate repair size are selected. Usually, the main and connecting rod bearings are replaced; if necessary, the crankshaft journals can be turned and restored. It is mandatory to service the valves, the condition of which at the time of the need for an overhaul of the engine almost certainly leaves much to be desired. In parallel with the general repair of the power unit, refurbishment of auxiliary components such as the starter and alternator is usually also carried out. As a result of the repair, the engine parameters return to the values characteristic of the new unit, while the latter will be able to reliably serve for many, many thousands of kilometers more.
Note. Critical cooling system components such as hoses, drive belts, thermostat, and water pump MUST be replaced with new parts during an engine overhaul. In addition, you should carefully check the condition of the radiator. If there are signs of leaks or obstruction, the radiator should also be replaced. Many branded service stations do not guarantee the operation of a remanufactured engine without professional cleaning and repair of the radiator. Also replace the oil pump.
Before proceeding with the overhaul of the engine, carefully read the materials of this Part of the Chapter in order to theoretically prepare for the upcoming work. Note that the overhaul of the engine does not require high professional training from the performer, but it takes a lot of time. You should plan to stop using the car for at least two weeks, especially if you need help from a mechanic shop to carry out some restoration work. Do a little marketing by checking the availability of the required parts, tools and equipment. Prepare all the necessary materials in advance. Most of the work can be done with the usual set of hand tools, however some of the checks to determine the suitability of individual components for further use require the use of precision measuring equipment. In doubtful situations, seek help from a car service workshop specialists who will always help you decide on the need to replace or rebuild any internal engine component.
Note. Before taking any of the parts for refurbishment to a car service workshop, carry out a complete disassembly of the engine and all its internal components. Do not forget that the decisive factor in the question of the advisability of overhauling the engine is the condition of its cylinder block. It is often cheaper and more reliable to replace a worn engine with a remanufactured one. Never proceed to purchase replacement components until you have thoroughly examined the condition of the unit. Remember that time is the main cost factor when performing an engine overhaul, and therefore, it is pointless to transfer it to the installation of worn-out or non-standard components and components.
In conclusion, we note that all efforts to perform the refurbishment of worn components will be wasted if the requirement for cleanliness during assembly of the unit is neglected.