The material offered to the attention of readers contains a wide range of information - from practical advice on purchasing the necessary spare parts to a detailed step-by-step description of the procedure for removing, checking the condition, repairing and installing internal engine components.
The procedure descriptions are based on the assumption that the engine is completely removed from the vehicle and installed on a mounting stand or sturdy workbench. All information related to engine repair procedures that can be performed without removing the latter from the vehicle (in situ) is given above-see. SOHC Gasoline Engine Repair Procedures Without Removing Them From The Vehicle, Repair procedures for DOHC gasoline engines without removing them from the vehicle and Repair procedures for 1.7L and 2.0L diesel engines without removing them from the vehicle.
It is not always easy to determine the moment when a major overhaul of the power unit is necessary. A whole host of different factors must be taken into account.
High mileage is not necessarily a sign that the engine needs a major overhaul. On the other hand, a short period of operation is also not a sufficient guarantee of the serviceability of the power unit. Perhaps the main factor determining the service life of the engine is the frequency and regularity of the general and current maintenance procedures 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 current 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 period of time.
Excessive engine oil consumption can be considered a signal that it is necessary to check the condition of the piston rings, valve stem seals and/or valve guides. Naturally, first of all, you should make sure that the oil loss is not associated with the development of its external leaks. Contact a qualified specialist who will help determine the general condition of your car's engine based on the results of checking the compression pressure in the cylinders and measuring the depth of vacuum at various initial parameters (please refer to the relevant sections).
Loss of developed power, disruption of rotation stability, excessive noise background of the valve mechanism, increased fuel consumption are usually quite characteristic signs of the need for a major overhaul of the engine, especially when all these factors appear simultaneously. If performing a full range of adjustments does not help in eliminating the problems, the only way out of the situation will be to carry out general mechanical work to restore the engine.
Major repairs of the power unit involve restoring all its operating parameters to the level typical of a new engine. During a major repair, piston rings are replaced and cylinder mirrors are restored (turning and/or honing). In case of cylinder boring, pistons of the corresponding repair size are selected. Main and connecting rod bearings are usually replaced; if necessary, boring and restoration of crankshaft journals can be performed.
Maintenance of valves is mandatory, the condition of which at the time of the need for a major overhaul of the engine almost certainly leaves much to be desired. In parallel with the general overhaul of the power unit, a refurbishment of such auxiliary components as the starter and generator is usually also carried out. As a result of the repair, the engine parameters return to the values characteristic of a new unit, while the latter will be able to reliably serve many, many thousands of kilometers.
Critical cooling system components such as hoses, drive belts, thermostat and water pump MUST be replaced with new ones when performing a major engine overhaul. In addition, the condition of the radiator should be carefully checked (see Chapter Cooling and heating systems). If signs of leaks or obstruction are detected, the radiator should also be replaced. Many branded service stations do not provide a guarantee for the operation of a rebuilt engine without professional cleaning and repair of the radiator. Do not forget to also check the condition of the oil pump (see SOHC Gasoline Engine Repair Procedures Without Removing Them From The Vehicle, Repair procedures for DOHC gasoline engines without removing them from the vehicle and Repair procedures for 1.7L and 2.0L diesel engines without removing them from the vehicle — relevant sections).
Before you start performing a major overhaul of the engine, carefully read the materials of this Section in order to theoretically prepare for the upcoming work. Note that a major 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 to seek help from a mechanical workshop to perform individual repair work. Do a little marketing by checking the availability of the required spare parts, tools and equipment. Prepare all the necessary materials in advance. Most of the work can be done using a regular set of locksmith tools, but some of the tests to determine the suitability of individual components for further use require the use of precision measuring equipment. In doubtful situations, seek help from specialists at the auto service workshop, who will always help you decide on the need to replace or repair any internal engine component.
Before taking any of the parts to a car service workshop for refurbishment, completely disassemble the engine and all its internal components. Remember that the decisive factor in the question of the advisability of performing a major overhaul of the engine is the condition of its cylinder block. It is often cheaper and more reliable to replace a worn-out engine with a refurbished one. Never start purchasing replacement components until you have thoroughly examined the condition of the block. Remember that time is the main cost factor when performing a major overhaul of the engine, and therefore, it makes no sense to transfer it to the installation of worn-out or non-standard units and components.
In conclusion, we note that all efforts to perform restoration repairs of worn components will be wasted if the requirement for cleanliness during assembly of the unit is not taken into account.
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