High mileage is not always an indication that a rebuild is necessary, nor is low mileage always an indication that a rebuild can be avoided. Frequency of maintenance is probably the most important factor. An engine that receives regular oil and filter changes, as well as regular maintenance, will likely provide many thousands of miles of trouble-free driving. Conversely, an engine that is not serviced will require a rebuild very quickly.
Excessive oil consumption is an indication that the piston rings, valve seals and/or valve guides need attention. Make sure the seals are OK before assuming the rings and/or guides are in bad condition. Perform a compression test on the cylinders to determine the work needed.
Remove the oil pressure sensor and check the oil pressure with a gauge inserted in its place. Compare the results with the specifications. If the pressure is extremely low, the bearings or oil pump are probably badly worn.
Lack of power, rough running, knocking or metallic sounds in the engine, loud valve noise and excessive fuel consumption may also indicate the need for an engine overhaul, especially if they are present at the same time. If a full tune-up and adjustment does not improve the situation, then the only way to solve the problem is to overhaul the engine.
Engine repair involves bringing the internal engine parts to a new condition. During repair, piston rings are replaced and cylinder bores are ground. When performing cylinder surface treatment in a specialized auto repair shop, it will be necessary to install larger pistons. Main and connecting rod bearings are usually replaced with new ones, and, if necessary, the crankshaft can be ground to restore the journals. It is usually necessary to resort to valve repair as well, since their condition usually leaves much to be desired. When performing engine repair, its external components, such as the starter or generator, can also be repaired. In the end, the engine should be as good as new, providing a large number of kilometers of mileage without problems.
CAUTION: Cooling system components such as hoses, drive belts, thermostat and water pump should always be replaced when performing major engine repairs. The radiator should be carefully inspected to ensure that it is not clogged or leaking. We also recommend that the oil pump be overhauled.
Before you begin rebuilding your engine, please read the entire process description carefully to familiarize yourself with the skills required to perform the job.
[The original material is posted on the website: mitsubishiman]
Rebuilding an engine may not be too difficult if you follow all the instructions carefully, use the necessary tools and strictly adhere to the control dimensions, but it can be quite time-consuming. Plan on keeping the car out of service for at least two weeks, especially if there are certain parts that need to be repaired at a specialist workshop. Check that you have the necessary parts and make sure that you have all the necessary tools and equipment ready in advance. Most of the work can be done using common tools, but special precision measuring tools are also required to determine whether certain parts need to be replaced. A specialist workshop can often take the necessary measurements and advise on the need for replacement and/or repair.
CAUTION: Always wait until the engine has been completely disassembled and all components (especially the engine block) have been inspected before deciding which operations should be taken to a specialist workshop.
Since the condition of the block is the main factor in deciding whether to rebuild an old piston group or purchase a new one, never purchase parts or machine parts until the cylinders of the block have been thoroughly inspected.
In conclusion, it must be said that in order to ensure maximum service life and a minimum number of problems on the engine after repair, it is necessary to carry out assembly very carefully and in conditions of complete cleanliness.