High vehicle mileage does not necessarily mean the need for major repairs, just as low mileage does not exclude it. Perhaps the decisive factor here is the frequency of maintenance. An engine that has had its oil and filters changed often enough and the required adjustment procedures performed will not give you trouble at high mileage. On the other hand, a running engine may very quickly need an overhaul.
Excessive oil consumption indicates the need to pay attention to piston rings, valve seats and/or valve guides. But before suspecting rings and/or guide bushings, check for oil leaks. Perform a compression pressure test to determine the extent of repairs needed (compression) in cylinders (see section 3).
Remove the oil pressure switch and measure the pressure using the control pressure gauge installed in its place (see illustrations). Compare the results with the specifications given in this chapter. The general rule of thumb is to increase engine oil pressure by 10 psi per 1000 RPM. Too low oil pressure may be due to worn bearings and/or oil pump.
2.4a. The oil pressure sensor on a 3.8L engine is located on top of the oil filter housing (indicated by an arrow). Remove sensor...
2.4b. The oil pressure sensor on the 3.1L engine is located at the front of the cylinder block between the oil filter and the starter
2.4c....and install an oil pressure gauge in the engine
Loss of power, uneven engine operation, knocking and "metal" engine noises, valve knocking and high fuel consumption can also indicate the need for an overhaul, especially if they occur at the same time. If all possible adjustments do not correct the situation, the only way out is to carry out repair work.
An engine overhaul involves restoring internal parts to match the specifications of a new engine. During a major overhaul, piston rings are replaced and cylinder walls are processed (reboring and honing). If reboring is carried out in a car repair shop, then new pistons of large (repair) sizes. Main bearings, connecting rod bearings and camshaft bearings are usually replaced and, if necessary, the crankshaft can be re-ground to restore the condition of the journals. As a rule, valves are also serviced, since their condition at the time of repair is usually far from ideal.
Note. Parts of the cooling system, such as hoses, drive belts, thermostat and cooling system pump, must be replaced with new ones when overhauling the engine. The radiator should be carefully inspected for possible leakage and blockage (see chapter 3, section 5). It is not recommended to repair the oil pump on a 3.1 liter engine - always install a new pump when repairing the engine.
Before starting an engine overhaul, examine all planned operations to familiarize yourself with the scope of work and existing requirements. Repairing an engine will not be too difficult if you carefully follow the instructions, have all the tools and equipment, and pay attention to specifications. Check the availability of the required spare parts and prepare the necessary tools and equipment in advance. Most of the work can be done with standard hand tools, although some precision gauges will be required to check the condition of parts when determining if they need to be replaced.
Note. Do not rush to decide what service and repair operations will be performed in an auto repair shop before you have completely disassembled the engine and checked all its parts, especially the cylinder block. Since the condition of the cylinder block is a decisive factor in deciding whether to overhaul or buy a remanufactured engine, do not purchase replacement parts or repair other parts until the block has been thoroughly inspected. Do not try to save money by installing worn or non-standard parts.
Finally, to ensure maximum remanufactured engine life with minimum problems, all assembly work must be carried out carefully and under impeccable cleanliness.