Knocking in the engine
If you feel that while the engine is running, you are starting to hear sounds (knocking) that were not there before, immediately check to see if everything is OK with the engine. Most often, engine knocking is associated with serious malfunctions, for the diagnosis and elimination of which it will be necessary to disassemble the engine in a car service or garage. However, you can try to determine the cause of the engine knocking yourself in order to decide whether to drive to the service station on your own or have it towed.
Attention! If you have the slightest doubt about self-diagnosis, get out the towing rope. Serious repairs to a damaged engine will cost more than a towing or recovery service.
Knocking of main bearings - very dangerous; turn off the engine immediately, you will have to be towed to a car service or garage. Low pitched knocking sound from main bearings. It can be heard in the lower part of the crankcase, and noticeably increases under load and with an increase in crankshaft speed. Often the appearance of knocking of main bearings is accompanied by a drop in oil pressure (the oil pressure warning light on the instrument panel is on almost constantly).
Knocking of connecting rod bearings - very dangerous; turn off the engine immediately, you will have to be towed to a car service or garage. The sound of connecting rod bearings is rhythmic, ringing, metallic, medium-tone. Increases significantly with increasing load and disappears completely when the spark plug is disconnected.
Knocking of piston pins - dangerous; without putting any strain on the engine, you can drive to the car service center or garage on your own. The knock of the piston pins is rhythmic, high-pitched, with a sharp metallic tint, audible in all engine operating modes and intensifies with increasing engine load. Disappears completely when the spark plug is disconnected. Knocking of worn pistons and cylinders - not dangerous; without putting too much strain on the engine, you can drive to the car service center or garage on your own. A sound reminiscent of the clatter of clay pottery. The knocking of worn pistons and cylinders is especially noticeable on a cold engine, and decreases or disappears as it warms up.
Valve knocking - not dangerous; you can get to the car service center or garage yourself. A metallic knock against the background of a general dull noise. The valve knock can be clearly heard at low and medium crankshaft speeds from the cylinder head side above the valve locations. Valve knocking is often confused with tappet knocking (the latter is very high pitched and variable in volume, almost unavoidable).
Detonation knocks - dangerous, but usually eliminated by replacing the knock sensor or filling with good quality fuel. By avoiding heavy engine load, you can drive to a car service center or garage on your own. A loud metallic knocking sound that usually occurs when the car accelerates. Causes: failure of the knock sensor, use of low-octane fuel, engine overload due to too early engagement of a higher gear, significant carbon formation in the combustion chambers. It is necessary to use a special fuel additive to remove carbon deposits on valves and in combustion chambers.
Knocking in suspension and transmission
If an extraneous knocking noise appears in the suspension of a moving vehicle, it is necessary to immediately determine its source, regardless of whether it is a constant knocking noise or appears only when driving over uneven surfaces.
Warning! Faults in the vehicle suspension can lead to a serious accident! Check the suspension according to the procedure described in section. "Chassis" (see "Checking the technical condition of the front suspension parts on the car").
It is quite difficult to diagnose the serviceability of transmission components based on the noise they make. If you are unable to accurately determine the source of the noise (knocking), contact a qualified specialist at a car service center.
Repair or replace any faulty transmission components (see section. "Transmission").
Vibration and shock on the steering wheel
Knocking and vibrations from underneath the car may be caused not only by faults in the suspension, but also in the steering.
Attention! The condition of the steering significantly affects not only the ease of driving, but also the safety of the vehicle.
The cause of knocking and vibrations on the steering wheel may be a faulty condition of the ball joints of the steering rods and steering mechanism, or the wheels of the car. Check the steering according to the procedure described in the subsection "Inspection and testing of the steering system on the car".
Helpful tips:
- A possible cause of vibration and impacts on the steering wheel when driving at speeds above 70-80 km/h may be an imbalance in the front wheels. Contact a car service or tire shop to check the front wheel balance.
- If shocks and vibrations on the steering wheel occur when the brake pedal is pressed, the brake pads must be replaced, and the front brake discs must be repaired or replaced (see "Replacing the front brake pads").
Possible causes of knocking in the suspension and ways to eliminate them
| Cause of malfunction | Method of elimination |
| The shock absorbers are faulty The bolts and nuts securing the anti-roll bar are loose, the cushions and rubber-metal hinges of the anti-roll bar are worn out Damage, deformation of rubber-metal hinges (silent blocks), upper shock absorber strut supports The shock absorber mounts are loose or the rubber bushings on the shock absorber lugs are worn out Wear of ball joints of front suspension arms Increased clearance in front wheel hub bearings Large wheel imbalance Wheel rim deformation Settling or breakage of the suspension spring Wear of rubber-metal hinges (silent blocks) rear suspension beams Knocking from suspension "breakdown" due to destruction of compression buffers Frequent breakdowns of the rear suspension due to overloading of the rear axle | Replace or repair shock absorbers Tighten the stabilizer bar mounting bolts, replace worn rubber pads Replace hinges, upper supports Tighten the mounting bolts and nuts, replace the bushings in the shock absorber eye Replace the ball joints Replace the front wheel hub bearings Perform wheel balancing Replace the wheel rim Replace the suspension spring Replace rubber-metal hinges (silent blocks) Replace damaged compression buffers Avoid overloading the suspension |
Possible transmission knocks (noises), their causes and methods of elimination
| Cause of malfunction | Method of elimination |
| Noise when clutch is disengaged | |
| Clutch release bearing worn or lacking lubrication | Replace the clutch release bearing |
| Noise when engaging the clutch | |
| Deformation or failure of the clutch driven disc components | Replace the clutch slave disc |
| Noise in the gearbox | |
| Low gearbox oil level Wear or damage to bearings or gears of the gearbox | Check the oil level, add oil to the gearbox if necessary Replace damaged parts |
| Noise when shifting gears | |
| Incomplete clutch disengagement Wear of synchronizers in the gearbox | Repair the clutch Replace the synchronizers in the gearbox |
| Knocking sound when the car starts moving | |
| Wear of constant velocity joints Increased clearance in the engagement of the main transmission gears | Replace faulty constant velocity joints Adjust the clearance in the main gear engagement |
| Knocking, clicking when the car is moving in a turn | |
| Wear of the outer constant velocity joint | Replace a faulty constant velocity joint |
Possible causes of vibrations and shocks on the steering wheel and ways to eliminate them
| Cause of malfunction | Method of elimination |
| Increased clearance in front wheel hub bearings Loosening the tie rod ball joint nuts Increased clearance in the ball joints of the steering rods Increased clearance in the steering gear Loosening of the steering gear mount | Replace the front wheel hub bearings Tighten the steering rod ball joint nuts Replace the tie rod ends Adjust the clearance in the steering gear Tighten the steering gear mount |