Knocks in the engine
If you think you hear sounds while the engine is running (knocks), which were not there before, immediately check if everything is in order with the engine. Most often, knocking in the engine is associated with serious malfunctions, for diagnosing and eliminating which you will have to disassemble the engine in a car service or garage. However, you can try to independently determine the cause of a knock in the engine in order to decide whether to go to a car service on your own or in tow.
Attention! If you have the slightest doubt about self-diagnosis, get the tow rope. Serious repair of a damaged engine will cost more than the services of a tow truck or a tow truck.
Knock of main bearings - very dangerous; turn off the engine immediately, you will have to go to a car service or garage in tow. Knock main bearings low tone. It is audible in the lower part of the crankcase, noticeably increases under load and with an increase in the crankshaft speed. Often the appearance of a knock on the main bearings is accompanied by a drop in oil pressure (The oil pressure warning light is on all the time on the instrument panel).
Knocking rod bearings - very dangerous; turn off the engine immediately, you will have to go to a car service or garage in tow. The sound of connecting rod bearings is rhythmic, sonorous, metallic, of medium tone. Significantly increases with increasing load and completely disappears when the spark plug is turned off.
Knock of piston pins - dangerous; without loading the engine, you can drive to a car service or garage on your own. The sound of piston pins is rhythmic, high-pitched, with a sharp metallic tinge, audible in all engine operating modes and intensifies with increasing engine load. Completely disappears when the spark plug is turned off. The sound of worn pistons and cylinders - is not dangerous; without heavily loading the engine, you can drive to a car service or garage on your own. A sound reminiscent of the clatter of pottery. The knock of worn pistons and cylinders is especially audible on a cold engine; as it warms up, it decreases or disappears.
Valve knock - is not dangerous; you can drive to a car service or garage on your own. A metallic thump against the background of a general muffled noise. The knock of the valves is well heard at low and medium speeds of the crankshaft from the side of the cylinder head above the valve locations. Valve clatter is often confused with tappet clatter (the latter is very high-pitched and variable in volume, practically irremovable).
detonation knocks - dangerous, but usually eliminated by replacing the knock sensor or refueling with good quality fuel. Avoiding a strong engine load, you can drive to a car service or garage on your own. Voiced metallic knocks that occur, as a rule, during acceleration of the car. Causes - failure of the knock sensor, the use of low-octane fuel, engine overload with too early upshift, significant carbon formation in the combustion chambers. It is necessary to apply a special fuel additive to remove carbon deposits on valves and in combustion chambers.
Knocks in the suspension and transmission
If an extraneous knock appears in the suspension of a moving car, it is necessary to immediately establish its source, regardless of whether it is a constant knock or appears only when driving through bumps.
Warning! Malfunctions in the suspension of the car can lead to a serious accident! Check the suspension according to the method described in sec. «Chassis» (see «Checking the technical condition of the front suspension parts on the car»).
It is rather difficult to diagnose the health of transmission units by the noise they emit. If you are unable to pinpoint the source of the noise (knocking), contact a qualified service technician.
Repair or replace damaged transmission components (see sect. «Transmission»).
Vibration and bumps in the steering wheel
The cause of knocks and vibrations from the bottom of the car can be malfunctions not only of the suspension, but also of the steering.
Attention! The state of the steering significantly affects not only the convenience of driving, but also the safety of traffic.
The cause of knocks and vibrations on the steering wheel may be a faulty condition of the ball joints of the steering rods and the steering mechanism, the wheels of the car. Check up a steering according to a technique stated in subsection «Inspection and testing of the steering on the car».
Helpful Hints:
- A possible cause of vibration and impact 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 balance of the front wheels.
- If shock and vibration on the steering wheel appear at the moment you press the brake pedal, you need to replace the brake pads, repair or replace the front brake discs (see «Replacing the front brake pads»).
Possible causes of knocks in the suspension and how to eliminate them
Cause of malfunction | Remedy |
Defective shock absorbers The bolts and nuts of the anti-roll bar are loose, the cushions and rubber-metal hinges of the stabilizer bar are worn out Damage, deformation of rubber-metal hinges (silent blocks), upper shock absorber mounts Loose shock absorbers or worn rubber bushings of the shock absorber eyes Wear of the ball bearings of the front suspension arms Increased clearance in the front wheel bearings Large wheel imbalance Wheel disc deformation Suspension spring settling or failure Wear of rubber-metal hinges (silent blocks) rear suspension beams Knock off «breakdown» suspension due to destruction of compression buffers Frequent «breakdowns» rear suspension due to rear axle overload | 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 ball joints Replace front wheel bearings Perform wheel balancing Replace rim Replace suspension spring Replace rubber mounts (silent blocks) Replace damaged compression buffers Don't Overload Your Suspension |
Possible knocks (noises) transmissions, their causes and solutions
Cause of malfunction | Remedy |
Noise when disengaged | |
Clutch release bearing wear or lack of lubrication | Replace clutch release bearing |
Noise when engaging the clutch | |
Deformation or failure of parts of the clutch disc | Replace clutch disc |
Noise in gearbox | |
Insufficient oil level in the gearbox Worn or broken bearings or gears in 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 clutch Replace synchromesh in gearbox |
Knocking at the beginning of the movement of the car | |
Wear of constant velocity joints Increased clearance in the gearing of the final drive gears | Replace faulty CV 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 defective CV joint |
Possible causes of vibrations and shocks on the steering wheel and how to eliminate them
Cause of malfunction | Remedy |
Increased clearance in the front wheel bearings Loosening the nuts of the ball pins of the steering rods Increased clearance in ball joints of steering rods Increased steering clearance Loose steering gear | Replace front wheel bearings Tighten the ball stud nuts Replace tie rod ends Adjust steering clearance Tighten the steering gear |