If increased noise or knocking is heard while the engine is running, the probable cause may be wear of the connecting rod or main bearing liners. Unscrew the pressure sensor and measure the oil pressure with a pressure gauge, compare the obtained value with the one specified in the technical data. If the pressure is low, the cause may be wear of the support bearings or the oil pump. Loss of power, engine failures, increased noise from the valve timing mechanism, and increased fuel consumption indicate the need for a major overhaul, especially if all these signs of malfunction appear simultaneously. If performing all adjustments does not lead to improvement, then repair is the most appropriate option.
A major overhaul involves restoring engine parts to the condition specified in the technical data for a new engine. During a major overhaul, the piston rings are replaced and the cylinder walls are bored (or honed) up to the repair size. After repairing the cylinders, new pistons will need to be installed. The connecting rod and main bearings must also be replaced; if necessary, the crankshaft should be ground to restore the clearances with the connecting rod and main bearings. As a rule, the valve mechanism is not replaced, since its condition at the time of repair is usually satisfactory. During a major engine overhaul, repairs are also performed on the carburetor, ignition distributor, starter and generator. As a result, the engine should have the qualities of a nearly new unit and serve reliably for a long time. Before starting a major engine overhaul, review the repair description to determine the scope of the work to be performed. Major repairs are not difficult, but they require a lot of time. It will take approximately two weeks, especially if it is for repair and restoration of parts (grinding, boring) you will have to contact a specialized workshop. Check the availability of spare parts and take care of purchasing the necessary special tools and equipment in advance.
Almost all work can be done using a standard set of tools, although precise measuring instruments will be needed to check and determine the suitability of certain parts. Often, the condition of parts is checked in specialized workshops, where recommendations for replacement or restoration of parts are received.
Since the condition of the cylinder block is a determining factor, a decision on further repair or the purchase of a new cylinder block should be made only after a thorough inspection of its technical condition. Make it a rule that the true cost of repair is time, then you won't have to pay for installing worn or repaired parts.
In conclusion, we note that the assembly of any units should be carried out very carefully, in a clean room, to avoid further failures of the repaired engine.
Original material on the website [Mazbook]
Important! You should only contact a car service center after completely disassembling the engine and inspecting all components, especially the cylinder block, to determine what maintenance and repair work will be performed.