Knock in the rear suspension: causes and solutions

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Structurally, the rear suspension of the car is much simpler than the front. However, this does not mean at all that there is nothing to knock on there. Knocking in the rear suspension usually becomes audible at the moment when repair is required. In the front chassis, you can feel the impact on the steering wheel, pedals, body, and the sounds are closer. In the rear, the sounds are reverberated into the trunk, where it is difficult to hear them. And when the driver needs to transport something long and the seats fold down, then the knock becomes well felt and the understanding comes that there is a problem. And if by the type of knock in the front suspension it is not difficult to understand what happened to the car, then in the case of the rear suspension, the diagnosis is more difficult. But you can understand the reason.

The easiest and most reliable way to diagnose a knock in the rear suspension is manually, but this is if it is not possible or you do not want to go to the service station. There are also diagnostic stands that will determine any suspension problems without errors. It’s not worth driving with knocks, although the rear suspension may seem not very important - inthis may lead to undesirable consequences in the future.

Knocking causes

Even in a simple rear suspension there are shock absorbers, springs, brackets and silent blocks. There is something to knock. If it knocks quite often, then you need to take a little time to diagnose.

What to check first?

You should start self-diagnosis not from the rear chassis, but from the exhaust system. Check the exhaust path from beginning to end. Very often, rear suspension thuds are caused by the muffler and not elsewhere. To do this, they drive the car into a pit or lift it on a lift, carefully check the fasteners and all the details of the exhaust system. Next, pump the exhaust pipe. If it does not make any sounds and does not hit the bottom, then everything is in order - you can move on.

Next check the trunk. Experts recommend paying special attention to the places where the spare wheel is attached. A tool can get into a niche and provoke sounds similar to the knock of a suspension. But if these checks did not give anything, then you need to move on and diagnose the elements of the rear chassis.

Checking fasteners

One of the most popular causes of knocks in the rear suspension is a beam. If the rear suspension in the car is exactly like this, then you can accurately determine what is knocking. The car is driven into a pit or overpass. Next, you will need the help of an assistant - he must rock the car. The driver must be in the pit and touch various nodesback beam. Most often, silent blocks of the rear beam knock. Knocking is also provoked by levers, but here the diagnosis is more complicated.

Checking the levers

The car is driven into the pit and a gear is set at the checkpoint - in this case it is better not to use the handbrake. For diagnostics, you need a mount. With its help, the serviceability of silent blocks and bushings in the levers is checked. If there are backlashes, then the bushings must be changed.

Suspension arms need to be checked for integrity. Often when driving, these parts are deformed. This can lead to knocking in the rear suspension. Cracks will indicate the need for urgent replacement of the levers. The lever fasteners can loosen during the ride - if so, they are tightened.

Deformed levers can knock when driving on the body. Knocking is also emitted by other parts in the rear suspension. This is determined by the buildup of the car.

This simple method of diagnosing buildup allows you to quickly and without serious costs get the most complete information about the state of the suspension. But you should not expect a miracle - not always the car will reveal all the secrets so easily. It happens that the knock of the rear suspension is heard while driving, but nothing is heard in the pit or at the service station.

Checking racks and supports

If the racks make a strange sound, it is determined quite simply. When the car is rocked, you need to attach the wooden handle of the hammer to the rack and feel if the knock is given to the object. May sound distorted or saggingsprings. Loose rack mounts can also really knock.

There are problems in the upper mount of the rack. The upper mount is broken - this can be seen from the trunk. You need to put your finger on the mount, and then rock the car up and down. If the lower fastener has lost its elasticity, this is checked in much the same way, but already on the bottom of the pit - a finger is applied to the fastener from below.

The rack itself may also fail. This is determined when all other options for the appearance of a knock in the rear suspension are excluded. Then you need to change the shock absorber on the car.

Next check the springs - they can make a variety of sounds. The coils beat against each other, there are various problems that lead to the breakage of the spring. To carry out a full diagnosis, you need to disassemble the parts, but this is usually done when nothing helps. Pay attention to the integrity of the rubber gaskets, which are sometimes installed from the factory on the top and bottom of the spring. They smooth out impacts on the body during suspension operation. If there are no such elements, it is likely that the sounds arise precisely because of this.

It often happens that a knock in the rear suspension appears only when driving, and during the diagnosis everything is in perfect order. Then the spring needs to be disassembled.

Brake Calipers

This situation is possible on some models of cars with rear disc brakes. The reason is loosening or play of the calipers. This is a common problem for budgetcar models. It is inexpensive fasteners that often lead to failure of parts. Often such knocks are very difficult to diagnose. You will have to perform a series of operations.

First of all, they pull the caliper with their hands when the wheel is screwed on. There is a chance that these parts are beating against the brake disc. But everything has to be tight. Then they remove the wheel and carry out a manual diagnosis of all caliper mounts - they pull the mechanism with their hands and check the backlash.

Next, the caliper is disassembled to reveal the relaxed details. Particular attention should be paid to the quality of the tightening of each module and element, each bolt. This may suggest the nature and cause of knocks. You also need to pay attention to the brake pads - they may be worn out or deformed and knock in place when driving.

In the case of drum brakes, everything is much simpler. None of the elements in this mechanism can provoke knocks. This is possible only when the drum has crumbled. But you don't need to discount the brakes, especially if you hear a knock in the rear suspension when braking. The pads have already been said and now we need to look deeper into the situation.

Brake Cylinder

Knocking can provoke a brake cylinder if it is not working properly. For diagnostics, the car is raised with a jack or on a lift, then they look at how the rear wheels grab when the brake is pressed. The cylinder can wedge and then hit the drum with a block. Next, the block returns to its usual position, but slowly. And at that moment, sounds are heard.

Brake force distributor

Knocks canbe provoked due to a malfunctioning "sorcerer". When braking hard, the rear will skid, as one wheel is skidding. The "Sorcerer" can jam, and he suddenly loads one of the wheels, and then does not want to let go.

What else can knock?

There are also the most incredible causes of knocks that drivers have been looking for for years and cannot find. If there is even a slight knock in the rear suspension, then over time it will intensify, and it can be localized. But worse, when this knock does not change. Additional checks needed.

Often the reason is a loose wheel after a tire fitting. Also in the trunk there may be metal parts that knock two against each other - in the cabin it seems that this is a knock in the suspension. The spare wheel can knock against the housing for it. The body itself can also knock. And the muffler - it vibrates a lot.

All these reasons are checked first at the service station. So you can understand where the knock of the rear suspension on small bumps comes from when driving, without even going to the suspension diagnostics. You just need to normally look for the cause and have more information on how to solve problems.