High mileage does not necessarily mean that an overhaul is necessary, and vice versa, low mileage does not eliminate the need for one. Regularity of maintenance is the most important factor to consider. An engine that has had its oil and filter changed regularly, and other required maintenance performed, will provide many thousands of kilometers of trouble-free service. Conversely, a poorly maintained engine may require rebuilding at very low mileage.
Excessive oil consumption indicates that the piston rings, valve stem seals and/or valve guides are damaged (however, the possibility of leaks should first be excluded). Perform a compression test to determine the likely cause of excessive lubricant consumption.
Check the oil pressure by placing the gauge in the working position of the oil pressure sensor and compare the obtained result with the data given in the Specifications. If this pressure is low, the main and connecting rod bearings and/or the oil pump are probably worn.
Loss of power, rough running, engine or valvetrain noise, and high fuel consumption may also indicate that the engine needs an overhaul, especially if all of these factors are present at the same time. If a full service course does not resolve the problem, regrinding the worn components is the only solution.
Engine overhaul involves restoration of all internal parts, replacement of pistons and piston rings. As a rule, new main and connecting rod bearing shells are installed; if necessary, the crankshaft can be replaced or reground; in addition, the valves are serviced. During a major engine overhaul, components such as the starter and generator may also be rebuilt.
Note: When overhauling the engine, the cooling system hoses, thermostat and water pump should be replaced. Inspect the radiator carefully to ensure it is not clogged or leaking. In addition, it is recommended to replace the oil pump.
Before you begin overhauling the engine, read the description of all procedures and prepare everything you need. If you carefully follow all the instructions and prepare the necessary tools and equipment, the work will not cause any particular difficulties, although it may take a lot of time. Check the availability of the required spare parts. The basic work can be done with common tools, but precision measuring tools will be needed to inspect parts and determine if they need to be replaced.
Note: Before deciding what repairs need to be performed, the engine must be completely disassembled and all components inspected (especially the cylinder block and crankshaft). The condition of these components is the main factor that determines whether an engine can be rebuilt or whether it should be replaced with a remanufactured unit. Do not purchase parts or attempt any repairs to any components until you have made this decision.
To ensure maximum lifespan of your rebuilt engine, ensure impeccable cleanliness during assembly.