During braking, knocking: possible causes, troubleshooting, and recommendations

At numerous thematic forums, motorists complain that from time to time they hear uncharacteristic sounds and vibrations during braking. This knock occurs in different situations. We will analyze the reasons for this unpleasant phenomenon, and also learn how to fix the problem.

Brake systems

This is one of the key security factors. It is with the help of brakes that the driver can reduce the speed of the car until it stops. There are several types of systems. The most common option - with a hydraulic drive. Here, the force from depressing the pedal is transmitted via the brake fluid to the actuators. They are on the hubs. As for the brake mechanisms themselves, two types of solutions are used in cars. These are the disc brakes popular today and the older version is drum. In the first mechanisms, the pads interact with a disc fixed to the hub. As for the second, they are inside the brake drum. The process of deceleration is carried out by the fact that the pads are unclenched and pressed against the inner planes of the drum.

Drum brakes are a rather old and archaic solution. But on budget cars they are still widely used. Also, a parking brake is implemented by means of the drum brakes. Thus, in front there are disk systems, and behind - drum.

About service

Like any other system in the car, the brakes need regular maintenance. In the case of a hydraulic mechanism, it is necessary to periodically replace the pads - they have the property of being erased. It is important from time to time to monitor the condition of both disks and pads. It is also necessary to regularly check and drum brakes. As for the drive itself, it checks the condition of the mains, visually diagnoses the system for leaks, and controls the level in the tank.

Also, after any work on servicing the brake system of the car, it is necessary to carry out the pumping. This is done in order to remove air from the mains. The presence of air in the pipeline can reduce the efficiency of the brakes, or even affect their performance. Since the system does not have a large number of different components, many consider it unusually reliable and think that with proper care it will not deliver the owner any serious problems. However, this is not always the case. Problems can arise in the designs of any complexity. One of the most popular problems in the case of brakes is characteristic sounds during braking. A knock occurs when the pedal is depressed.

Features

These sounds can have a very different character. They can be heard from different sides of the car, also occur in a certain position of the pedal. A knock can be either single or repeating. Most often during braking, a knocking in front is heard after any maintenance of the brake system. It is very difficult to diagnose problems in brake mechanisms by knocking. Even if something vibrates, it does not necessarily mean that it will be a brake system. Sounds can produce leaking racks and failed rear shock absorbers, fastening elements of the anti-roll bar and many other components.

About the difficulties of diagnosis

In addition to the brake system, it is worth checking the faults in the wheel drives - this is indicated by a knock in the front suspension when braking. This is a fairly common phenomenon that motorists face. Experts argue that often the culprits of suspicious sounds can be even a steering system and an engine cushion. This is why fault diagnosis is a very complex process. One of the typical features of the emergence of sounds during braking is the knocking out only in the pedal, which is squeezed out halfway. If you squeeze it into the floor during intensive braking, then extraneous sounds will disappear. Often, car owners write on the forums that this sound can be heard when driving at low speeds, also on medium. On high - less often. In most cases, you can not hear anything until the brake mechanism is cold.

Another point that complicates the diagnosis is the frequency with which a knock occurs during braking in the front wheel or the rear wheel. He can be heard for some time, then - completely disappear and after a while appear again. Now many cars are equipped with ABS - sometimes a malfunction can be in it. But this is not a fact. Even self-diagnosis systems are not able to find errors in the operation of the anti-lock system.

Typical causes of knocking in brake mechanisms

Consider the typical causes of knocking and other extraneous sounds. In fact, there are few such reasons. You can eliminate them yourself.

Backlash guide rail

One of the most popular causes of knocking is the worn out seats for mounting the slide guides in the braking mechanism. In this case, the support appears backlash, which causes vibration during braking. Knocking is also often manifested. Solving this problem is very simple - it completely disappears after replacing the guides.

Chocking the caliper piston

During the braking process, the liquid presses the piston. However, the driver jams in the cylinder and is in this position until the pressure build-up pushes the piston out of it. When this happens, he strikes the pads with force and presses them - this is the reason why when knocking down a knocking in front is heard.

To fix this situation and get rid of annoying sounds, just remove the caliper and remove the piston. Then visually check its condition, and together with the piston inspect the surface of the cylinder. If corrosion is found during the inspection, the cylinder must be cleaned and the piston is recommended to be replaced.

Brake disk

Often a knock at braking in a forward wheel arises because of curves of disks. This occurs in case of overheating. In the process of braking, the pads, passing through the place where there is a bend, beat against it, which causes a knock.

This problem is treated, but it is quite difficult to accurately detect deviations from the norm without special equipment. With strong defects, of course, everything can be seen visually, but then it's better to replace the disk with a new one. You can also pierce the surface of the disc on a lathe or with special tools. Pads are better to replace, otherwise after the restoration of the disk they will again make it work. Sometimes the curvature of the disc can be guessed by the state of the pads. Their wear will be uneven.

Knocks in the Drum Systems

In such mechanisms, there are a sufficient number of places where there may be a knock at the rear during braking. Often such a mechanism is the parking brake. Since under the car the cable of the parking brake system diverges into two parts, it may well be that one of the parts has relaxed. The mechanism is weak, and when the driver presses the main brake pedal, the drum pads disperse. Between the pads and the stop bar of the parking brake there is a backlash, which is the cause of the knock.

Also, the distributing part often knocks. If at least one of the cables is not tight enough, then the bar will vibrate and the driver will hear a knock when braking in the rear wheel. Another reason is the pad lock. If it comes out of its seat, the shoe will move - this will provoke a blow on the drum. Rarely, the vibration caused by a loose hub bearing may cause a vibration . But more often it's just noise. It manifests itself at low speeds precisely when braking. Also, a rather rare reason - long wheel bolts. Longer - clings in the process of braking. The problem is solved elementary - replacing the bolt with a short one.

In models built on the popular platform B0, in the process of operation the back mechanisms start to creak. The reason is banal - the brake shoe rubs against the shield. To diagnose simply - remove the retainer, then remove the shoe. The wipes will be visible to the naked eye. To treat this situation is also very simple - the damaged area should be cleaned and greased with grease. And then the sounds will disappear.

Knocking in brakes with ABS

On vehicles equipped with ABS, you can easily check whether it is the cause of the knock. To do this, pull out the fuse, which is designed to operate the system. At the same time the system will stop working, but the brakes will function. If, during braking, a knocking in front or behind disappears, then ABS is to blame.

Suspension and other elements

Suspension is the next element that needs to be carefully checked. It often happens that the problem was not hidden in the braking mechanisms. Various details of the suspension may well produce knocking and other unpleasant sounds to the driver.

Silent blocks and bushings

These parts with high wear can cause a characteristic sound. If the silentblock is worn in the steering mechanism, then it will knock. Finally, it is recommended to check the engine cushions and its mountings. It is enough only a small indulgence, so that in the cabin everything went "walker".

SHRUS

If the knock is clearly heard during the starting and braking, the first step is recommended to diagnose the CV joints. Pay attention to the sounds when turning the wheels for the first time. If you hear a knock, then the problem is in the running gear of the car. Also among the reasons can be identified a broken hinge of equal angular velocities, a failed steering linkage, a worn rake. By the way, the latter can flow if a malfunction occurs - it is worth paying attention to anthers. Perhaps they are out of order. Also, vibrations can say that soon it is necessary to replace ball bearings and struts of shock absorbers.

Summary

The braking system is the basis for driving safety on the car. In the event of the slightest malfunction in its operation, it is necessary to search for a malfunction without delay and to solve the problem. In fact, there are not so many reasons. In addition, everything can be much easier - for example, a knock on the wheel when braking occurs due to the unscrewed bolt securing the caliper.