What Does The Abnormal Noise Of The Drive Belt Represent?

Squeak

The belt makes a squeaking noise, which generally indicates that the friction coefficient of the belt surface is greatly reduced and the belt has been excessively worn. If it makes a noise when the vehicle is loaded, you can observe one of the transmission belts. You will find that the resistance or elasticity on the belt, the automatic belt tensioner or the belt tensioner will increase abnormally.

Most automatic belt tensioners have a set of belt wear length indicators somewhere along the slide way between their bottom and the tensioner arm. This sign consists of a pointer and two to three marks, which indicate the working range of the belt tensioner. If the pointer exceeds this range, the belt may be stretched too long and should be replaced.

On vehicles without automatic belt tensioners, measure with a standard belt elongation measuring ruler at the middle of two belt pulleys. If it is different from the standard value, it is better to replace the belt.

If the elongation of the drive belt does not exceed its limit value, then if your car is equipped with an automatic tensioner, you should focus on it. First, start the engine, load the auxiliary transmission mechanism as much as possible (such as turning on the light, air conditioner, turning the wheel, etc.), and then observe the belt tensioner cantilever; When the engine is working, the belt tensioner suspension pipe should have a small displacement. If the belt tensioner cantilever does not move, turn off the engine and move it manually within the working stroke of the belt tensioner suspension tube, with a displacement of about 1/4 inch. If the belt tensioner cantilever cannot move, it indicates that the belt tensioner is invalid and should be replaced in time; If the displacement of the belt tensioner cantilever exceeds 1/4 inch, it indicates that the spring load is too small and the belt will slip. If this is still the case, only replace the belt tensioner.

If the belt is not excessively stretched and the automatic tensioner is in good condition, check whether the working surface of the belt is polished as smooth as a mirror. This is a typical phenomenon of slipping under load caused by excessive belt wear. The peeling paint on the pulley surface is the best proof of the phenomenon.

If the belt squeaks only in wet weather, and the surface of the belt and pulley is relatively smooth. Let's do the same test: let the drive system of the auxiliary mechanism work under load, and sprinkle water on the belt with a watering bottle. If there is a noise, replace the belt.

Long scream or harsh noise

Although the belt may emit long squeal or harsh noise due to dirt such as sand on the pulley surface or reverse installation of used belt, it is usually caused by improper assembly of auxiliary mechanism drive device.

If the above noise occurs on a new car that has been driving for a short time, it may be caused by the poor assembly quality of the original manufacturer. Check the relevant components that you think may cause the failure. If the above noise occurs on an old car, you should consider whether some relevant parts of its auxiliary mechanism driving device need to be completely replaced. Carefully observe the components that may have been replaced (such as alternator, power steering pump, etc.) to see if their mounting brackets are firm and reliable. At the same time, pay attention to whether any washer or bushing is dropped during installation, which may also cause misalignment of pulley assembly.

It is mentioned that dirt or sand particles between the belt and pulley can also cause the above noise, so if the vehicle is working in a dirty environment, check whether there is dirt on the surface of all pulleys. The boom in buying air has told me that it is very necessary to do so.

Take the timing gear belt for example. It should be adjusted immediately after installation. This is why the rotation direction of the timing gear belt should be marked. If the timing gear belt is removed and installed reversely due to other maintenance work, you will hear a sharp, harsh scream when the belt is running. You try to reverse the installation direction of the belt to see if the fault disappears.

Hiss, rattle, growl, or whine

The continuous hiss or rattle that increases with the increase of engine speed usually means that the bearing of the auxiliary transmission mechanism is short of oil. With the help of a stethoscope, you can further listen to these noises. Then remove the drive belt and turn the suspected faulty components by hand. If it is difficult to rotate, or the sound is rough and harsh, or rattling, do not hesitate to replace the bearing or the corresponding parts. However, it should be noted that every time you replace the components of the auxiliary transmission mechanism, you must remember to replace the belt tensioner and the automatic tensioner.