Recommendation: The engine condition should be monitored regularly during vehicle operation. Signs of malfunctions may include: the presence of oil drops where the vehicle is parked; the engine malfunction indicator lamp or the oil pressure warning lamp comes on, and an extraneous sound appears (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 check must be carried out. Checks of the technical condition of engine systems are shown in the relevant sections of the chapter "Engine and its systems" (cm. "Cooling system - technical condition check"; "Power supply system - technical condition check"; "Engine Management System - Technical Condition Check"; "Exhaust system - technical condition check").
The technical condition of the engine can be assessed with sufficient accuracy based on external signs and using available equipment (compression gauge, pressure gauge for checking pressure).
Sequence of execution
1. Prepare the car for work (see "Preparing the car for maintenance and repair").
[The article is taken from an online resource: VAZBOOK.RU]
2. Inspect the engine from above and below (on an inspection pit or overpass). Oil leaks may indicate wear of the oil seals or oil pan gaskets.
3. Start the engine, and the oil pressure warning light should go out. If the warning light comes on at idle after the engine has warmed up and goes out after the crankshaft speed increases, the following may be worn: oil pump gears, crankshaft journals, main and connecting rod bearing shells. If the light is constantly on, the lubrication system or the oil pressure warning light may be faulty. Check the oil pressure in the engine lubrication system using a pressure gauge (see "Lubrication system - checking oil pressure").
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 malfunctions 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, we use a stethoscope to determine the zone 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 possible malfunction.
Note: A clicking, ringing sound under the cylinder head cover usually indicates increased clearances in the valve drive (see "Adjusting valve clearances in the timing drive"), a uniform noise in the timing belt area may indicate wear of the tension roller or coolant pump bearing. Knocks in the lower part of the cylinder block and from the oil pan, increasing with increasing crankshaft speed, are caused by a malfunction of the 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 with increasing speed, its tone increases. When you press the gas pedal sharply, the engine makes something like a growl - like "gyr-r-r". 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 in the upper part of the cylinder block on an unheated engine, which subsides and disappears when warmed up, can be caused by worn pistons and cylinders. Operating a car with faulty bearings and pins will lead to engine failure.
6. If oil consumption has increased and no signs of leakage are found:
- We warm up the engine to operating temperature.
- Disconnect the crankcase ventilation hose from the throttle valve.
- We bring a sheet of paper to the hose. If oil stains appear on the paper, then the cylinder-piston group is worn out. We determine the degree of wear by the compression in the cylinders (see "Compression in engine cylinders - check").
- If there is no oil mist coming from the ventilation system, 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.
Warning! Running the 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.