All instructions provided assume that the engine has been removed from the vehicle. Information regarding engine repairs in the engine compartment and removal and installation of external engine components is provided in Chapter Engine repair and in the Section Disassembling the cylinder head from this Part.
General description of engine overhaul
It is not always easy to determine whether an engine needs to be rebuilt, as it depends on many factors.
High mileage does not necessarily mean that an overhaul is necessary, and conversely, low mileage does not eliminate the need for one. Regularity of maintenance is the most important factor to consider. An engine that has had regular oil and filter changes and other required maintenance performed will provide many thousands of kilometers of trouble-free service. Conversely, a poorly maintained engine may require an overhaul at very high 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 ruled out). 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 specified 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 to be overhauled, especially if all of these factors are present at the same time. If a full service does not resolve the problem, regrinding the worn components is the only solution.
Engine overhaul involves restoring all internal parts, replacing 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 overhaul of the engine, components such as the starter and generator may also be tweaked during the overhaul.
Note: When rebuilding the engine, the coolant hoses, thermostat, and water pump should be replaced. Carefully inspect the radiator to ensure that it is not clogged or leaking. It is also recommended to replace the oil pump.
Before you begin overhauling the engine, read the procedure and gather all the necessary materials. If you follow the instructions carefully and gather the necessary tools and equipment, the job should not be too difficult, although it may take a long time. Check for the availability of the necessary parts. The basic work can be done with common tools, but you will need precise measuring tools to inspect the parts and determine if they need to be replaced.
Note: Before deciding what repair procedures need to be performed, it is necessary to completely disassemble the engine and inspect all components (especially the cylinder block and crankshaft). The condition of these components is the main factor that determines whether an engine can be rebuilt or replaced with a remanufactured unit. Do not purchase parts or attempt to repair any components until you have made this decision.