Recommendation. The engine condition should be monitored regularly during vehicle operation. Signs of malfunctions may include: the presence of oil drops where the car is parked; the engine malfunction indicator lamp or the emergency oil pressure indicator lamp comes on, the appearance of extraneous sounds (noise, knocking) when the engine is running; smoky exhaust; moving the temperature indicator arrow into the red zone; increased oil consumption, noticeable loss of power. If at least one of the listed signs is detected, a more detailed examination must be carried out. Checks of the technical condition of the engine systems are shown in the relevant sections of the chapter "Engine and its systems" (cm. "Checking the technical condition of the cooling system"; "Checking the technical condition of the power supply system"; "Checking the technical condition of the engine management system"; "Checking the technical condition of the exhaust system").
The technical condition of the engine can be assessed with sufficient accuracy based on external signs and using available equipment (compression gauge, manometer, technical stethoscope).
Sequence of execution
1. Prepare the car for work (see "Preparing the car for maintenance and repair").
2. Inspect the engine from above and from below on an inspection ditch or overpass. Oil leaks may indicate wear of seals or gaskets.
3. Start the engine, and the oil pressure warning light should go out. If the control lamp lights up at idle after the engine has warmed up and goes out after the crankshaft speed increases, then the following may be worn: oil pump gears, crankshaft journals, main and connecting rod bearing shells. If the lamp is constantly on, the lubrication system or the oil pressure sensor may be faulty. We check the oil pressure in the engine lubrication system using a pressure gauge (see "Oil pressure - check").
Warning! Operating the vehicle with insufficient oil pressure in the lubrication system will result in serious engine damage.
4. After the engine has warmed up, listen to its operation.
Recommendation. It is convenient to diagnose engine faults by ear using a technical stethoscope. With its help, you can quite accurately determine the source of extraneous noise.
Caution: To avoid injury, do not touch moving engine parts while performing the following operation (pulleys, belt) and do not touch hot engine parts.
5. When an extraneous sound appears, use a stethoscope to determine the area where this sound is most audible. Based on the nature of the sound and the location of the sound emission, we determine the possible source of the sound and the possible malfunction.
Note: A clicking, ringing sound under the cylinder head cover usually indicates a faulty hydraulic compensator in the valve drive (see "Hydraulic tappets - removal and installation"), uniform noise in the timing belt area may indicate wear of the tension and guide roller bearings or the coolant pump bearing. Knocking sounds in the lower part of the cylinder block and from the oil pan, which increase with increasing crankshaft speed, are caused by faulty main bearings. In this case, as a rule, the oil pressure in the lubrication system is low. At idle, this sound is low-pitched, and as the revs increase, its pitch increases. When you press the gas pedal sharply, the engine makes something like a growl like "gyr-r-r". The ringing knocks in the middle of the cylinder block are caused by a malfunction of the connecting rod bearings. A rhythmic metallic knock in the upper part of the cylinder block, audible in all engine operating modes and increasing under load, is caused by a malfunction of the piston pins. A muffled knocking sound from the top of the cylinder block on an unheated engine that subsides and disappears as it warms up can be caused by worn pistons and cylinders. Operating a vehicle with faulty bearings and pins will result in engine failure.
6. If oil consumption has increased and no signs of leakage are found:
a) warm up the engine to operating temperature.
b) disconnect the crankcase ventilation hose from the throttle valve.
c) bring a sheet of paper to the hose. If oil stains appear on the paper, the cylinder-piston group is worn out. The degree of wear is determined by the compression in the cylinders (see "Compression in engine cylinders - check").
d) if no oil mist comes from the ventilation system, then the reason for the increased oil consumption may be wear of the oil scraper caps (see "Valve stem seals - replacement"). In this case, the car will have smoky exhaust.
Operating an engine with a worn cylinder-piston group, faulty oil seals or on low-quality fuel leads to failure of the catalytic converter and oxygen concentration sensor.