Knocking crankshaft bearings
Usually a dull tone, metallic. Detected when the throttle is suddenly opened at idle. Its frequency increases with an increase in the frequency of rotation of the crankshaft. Excessive axial clearance of the crankshaft causes a sharper knock with uneven intervals, especially noticeable with a smooth increase and decrease in the crankshaft speed.
Knocking rod bearings
Usually the knock of the connecting rod bearings is sharper than the knock of the main bearings. It is heard at idle speed of the engine with a sharp opening of the throttle valves. The place of knocking is easy to determine by turning off the spark plugs in turn.
Attention: when disconnecting the spark plugs, connect the high-voltage wire to the arrester, in order to avoid failure of the elements of the engine electronic control system.
The knock of pistons
The knock is usually not sonorous, muffled; called «beating» piston in the cylinder. It is best heard at low engine speeds and under load.
Knocking inlet and outlet valves
Increased clearances in the valve train cause a characteristic knock, usually at regular intervals; its frequency is less than the frequency of any other knock in the engine, since the valves are driven by a camshaft whose rotational speed is half that of the crankshaft.
Excessive Camshaft Drive Circuit Noise
From the general noise of the engine, the noise of the camshaft drive circuit stands out when gaps appear between the gearing elements and is clearly audible at a low crankshaft speed.
Insufficient oil pressure at idle with a warm engine
Excessive oil pressure on a warm engine
Increased oil consumption
Engine overheating
The pointer of the coolant temperature gauge is in the red zone of the scale. Before troubleshooting, make sure that the coolant temperature gauge and its sensor are working (see subsection «control devices»).