Why does the front suspension knock on small bumps?

Front suspension installed with defects

A possible reason for the appearance of knocking on bumps may be the occurrence of defects in the lever system. At the same time, you will notice changes for the worse in the car's handling. The only culprit in this situation is a set of silent blocks.

To check for problems, you need to diagnose the levers. You can do it yourself using a regular mount. To do this, use the pry bar as an extended arm to create a counterweight and bend each of the arms in different directions. If you find significant play in the structure (discrepancy of more than 5-7 cm), then it is worth carrying out maintenance on the suspension.

If the machine has a collapsible structure, then you only need to replace the old set of silent blocks with a new one. The replacement process is as follows:

• First you need to dismantle the levers;
• Then the stage of pressing out the set of silent blocks from the fixed holes occurs. To do this, use a special mandrel;
• Install a new set of silent blocks, having previously generously lubricated each of them to reduce friction during operation. Also, do not forget to clean the mounting surface of the suspension from all dust and dirt before installation.

Front suspension

Tip: If the suspension was supplied with defects from the manufacturer, then in case of an unexpired warranty, you can contact the dealer, and he will be obliged to replace the defective parts free of charge. Also be sure to check the rear axle of the VAZ-2107.

How to check silent blocks?

A flat mount will be required for diagnosis. This will allow you to determine how badly these parts are worn. Using the mount, the lever will move in the longitudinal and transverse directions. If there is play or damage, then the front suspension silent blocks are to blame for the knocking.

Sometimes the levers can be collapsible. Then you can replace it with a silent block. To do this, the lever is dismantled, and then, using a special mandrel, the part is squeezed out. It is advisable to lubricate the new silent block before installation. The seating surface must also be cleaned. After installation, the knocking should stop.

The appearance of malfunctions in the steering

According to experts, the occurrence of knocking on small bumps in the suspension in 70% of cases is associated with the presence of obvious problems in the vehicle components. However, many drivers believe that the problem is related to the shock absorber struts, although the fault lies in defects in the steering.

An external examination and diagnosis of the steering rack will help to find out whether this is true or not. When checking this unit, you will also hear a similar knocking sound as the shock absorber. In this case, you will hear a knock only on one side. Also, an additional symptom that indicates problems in this element is the presence of slight vibration in the steering wheel. Vibration is usually noticeable when driving on gravel roads.

Tip: the sound occurs when the rotating gear rubs against the steering rack structure. This may be a side effect of replacing the wheel bearing on a VAZ-2109.

The problem with the steering rack is the following - the gap between the gear and the rack gradually increases, and the intensity of the element’s operation increases. As a result, during long-term operation of the vehicle, significant wear is formed on the body of the mating surfaces of each pair.

To check the fastening of the steering rack, you need to use a jack to lift one of the sides at the front of the car and use a pry bar to “stagger” each of the steering rods in different directions. At the same time, observe the behavior of each node. If you notice the appearance of play, then the appearance of a prolonged dull knock in the front suspension on bumps is associated with high wear of the bushing set. In addition, when you turn the steering rack, you will see a gap appear in each pair.

The solution to this problem is to carry out work to eliminate the gap by tightening the steering rack to the gear structure. And a set of bushings, which have become more worn out during operation, can be easily replaced with a new one. To do this, remove the rack from the body and change the bushings.

If the steering rack and bushings are in perfect order, but the steering wheel vibrates strongly on small bumps, then the problem should be looked for in the steering joints. A partner is required to check this part. Diagnostics is carried out in stages:

1. Remove the steering rack from the housing;
2. Secure the hinge structure, pin and body using a mounting tool;
3. Ask your partner to make sharp jerks when turning the steering wheel at a small angle of rotation.

As a result, unnecessary play between elements will be immediately identified by you. This way, you can replace a specific component, and the repair will cost much less than a full replacement of the front suspension.

Advice: as soon as you replace the faulty joints, start the car and try driving again on an uneven road. If there are no sounds or vibrations in the steering wheel, it means that the problem with the joints has been resolved. However, if the car stalls while driving and does not obey the steering wheel, the problem must be looked for elsewhere.

Carrying out repair work

Correctly diagnosed knocking in the suspension when starting and braking can be eliminated on your own. When carrying out repairs or replacing worn components, you do not need to stock up on special tools. All you need is a puller to remove the ball joints. The wheels are hung from the front and removed after unscrewing the disc mounting bolts.

The stabilizer nut is unscrewed using a socket or socket socket measuring 22 mm. It is necessary to clean the threaded tip with a metal brush in advance, treating it with a special penetrating liquid or oil. Similar actions are performed on the other side.

On the left and right, the nuts holding the two ball pins of the left and right support are removed. The operation is carried out with a 19 mm wrench, preferably a socket or socket wrench. Use a powerful screwdriver or chisel to bend the plates securing the bolts that hold the ball joints on the steering knuckle. Using a 13 mm wrench, we move the bolts screwed into the knuckle body from their place, without unscrewing.

Operations are carried out with caution. Once the bolts are broken, it will be extremely difficult to remove them.

It is necessary to slightly ease the tension of the threads by hitting the head of the bolts with a hammer, rocking them, remove the bolts from their places, and using a 13 mm socket, unscrew the two bolts securing the stabilizer bracket on the left and right to the cross member of the front engine mount.

Remove the cup from the stabilizer. Using a screwdriver, remove the rear hinge from the rubber. By pulling the edge of the stabilizer inward, release the tip from the mounting hole, and remove the support ball pin from the lever. To perform this operation, the suspension arm is pressed down with a crowbar, and it must be hit hard with a hammer.

You can use a special puller if available. Next, you should completely unscrew the bolts, removing the supports. It is necessary to unscrew the nut holding the bolt securing the lever to the underbody. Rock the lever, pull out the bolt, then the lever. Replace worn components, assemble, install in place.

Problems with the rack supports

The upper parts of the supports suffer the most when driving on uneven roads. In this case, most often it is necessary to replace the rubber base, which is necessary to dampen vibration and the resulting excess noise. The sound occurs as a result of loss of flexibility and severe wear of the base.

Often, when sounds appear, the driver begins to manually sort out the entire front suspension, spending a lot of time and money on new spare parts, but the cause of the noise does not disappear. You can identify the presence of a problem in the rubber base by simply measuring the gap distance between the support structure and the plastic stop. On average, the value of this parameter should be 8-10 mm.

To replace the rubberized base, contact a car service center - here they will carefully remove the support and install a new layer of rubber. In this case, noise and vibration will go away immediately, and the new “layer” will last another 20-40 thousand km.

The appearance of faults in the support bearing

The sound from a malfunction in this element is similar to the sound from the development of a damper, but it seems much louder. To detect a breakdown in the bearing, you simply need to remove the strut and inspect the integrity of the element. You will find that it is heavily worn on only one side, because the wear cannot be the same across the entire area of ​​the bearing. The greatest wear is visible when the vehicle is moving smoothly, without any turning.

While driving, it is quite easy to detect problems with the bearing - the knocking noise appears when the car is driving straight, and disappears when the car turns right/left. Also, when the bearing wears out, high vibration is felt when turning the steering column.

Is it possible to drive a car that knocks when starting off?

Since a single knock when starting off can be a consequence of various reasons, the possible consequences of ignoring the problem also differ. The nature of the manifestation of sound also matters. If you hear a knocking sound when you pull away sharply, but there is no noise during a smooth start, most likely the wear of the part is minimal and no urgent repairs are required. When the sound is clear and constant, you need to quickly look for and eliminate the cause.

If, when starting from a stop, a knocking sound occurs due to malfunctions of the steering, brakes, ball joints or wheel fasteners, further operation of the car is dangerous, since at any moment the car can become uncontrollable and provoke an accident!

In the table below, the causes of a single knock when starting off are sorted into groups depending on the danger of the consequences of operating the car in the event of malfunctions of the corresponding components.

The appearance of malfunctions in ball joints

Experts call this suspension unit the most common source of “classic” knocking in the front suspension of a car. However, this type of “disease” has its own specifics, since it mostly affects rear-wheel drive vehicles.

The main problem lies in the fact that the appearance of wear on the hinge structure causes a beating when the car moves over uneven roads. You can check this as follows:

• First, the wheels on the problem side are suspended;
• Next, with the disk locked, you need to make several sharp turns to the right/left from the vertical support;

Advice: in order to exclude any influence from the set of bearings located in the hub, ask your partner to press the brake pedal all the way when diagnosing the unit.

• When knocking occurs, faulty areas will be immediately found.

It is also necessary to check the set of boots attached to the ball joints. If the boot is significantly damaged, the service life of the hinge system is reduced by 2-3 years.

Chassis SS20

Life hack: clearance of a Priora car
These spare parts for domestic and foreign cars are produced under the “System Technologies” brand. These racks have become so popular due to their high quality. For Priora, the manufacturer offers 4 product options that differ in hardness. Which stands are better? They need to be selected according to your driving style. The softest ones are the “Standard” series racks. Rear shock absorbers from the same series are also offered.

A reinforced version is offered to increase the load capacity. Next are the “Comfort” racks. According to reviews from many car owners, this is the best option. They are stiffer than the Standard, but the suspension works equally well on bad and good roads.

The “Highway” kit is suitable for those who like stiff suspension and high speed. With these racks you can drive on bad roads, but it will be uncomfortable. “Sport” is the toughest option from this manufacturer for Priora cars. A front suspension of this type is not very suitable for the city, but for sports competitions it is just right.

Troubleshooting in the rack

Basically, the strut can make a knock and transmit impacts from uneven roads only when the entire structure is severely worn. Moreover, this element of the car suffers the most when the front pair of wheels falls into a deep hole - the rebound strut does not work, but the spring undergoes a sharp straightening. As a result, the wheel will go sharply down, stretching the spring to the maximum possible length. Thus, it turns out to be 2 hits - the racks against the support and the racks with the bottom of the pit.

Checking the functionality of the support pillar is carried out in a standard way - the vehicle is swung vertically or a partner presses forcefully on the central part of the hood. If the rack is in good condition, the body of the machine should return to its original state once without sharp straightening.

If the case falls sharply, you will hear a dull thud. This indicates a malfunction of the element due to a loose lock nut, which makes noise inside the support post itself. Repair of the rack should only be carried out at a car service center, since special equipment will be used to secure all elements in a high-quality manner.

If a knock occurs on small bumps due to the strut, the car sways strongly when moving and loses control. This may result in an accident on uneven roads.

Also, problems may lie not in the strut itself, but in the shock absorbers. A malfunction of the shock absorber system is primarily due to improper treatment with oil. Drivers often pour an oil solution with incorrect viscosity characteristics inside. This value is affected not only by the purchased oil, but also by the ambient temperature at which the solution is poured. Too low a temperature does not allow the oil fluidity to increase to the required value.

Weak points that often knock when starting on popular cars

Some car models have design features and defects that often cause knocking at start-up. The most likely causes of knocking noises when starting off on popular cars are collected in the table.

The appearance of malfunctions in the engine mount

In order to detect problems in the condition of the motor support, it will be enough to conduct only a visual external inspection. At a high level of wear of this element, you will find the appearance of significant tears, as indicated in the photo below.

The broken support is shown on the left, and the new support is shown on the right. As a rule, problems with the engine mount can occur after 100 thousand km of the vehicle. In addition, noise in the supports may be accompanied by vibration of the engine itself. In this case, you may find black carbon deposits on the spark plugs. To determine the specific cause of knocking and shaking, conduct a detailed diagnosis of all vehicle systems.

Advice: remember - timely repairs (even if there is slight noise on small bumps, holes and uneven surfaces) will guarantee the durability of the car's front suspension in the future.

FAQ

• Why does a knocking sound in a car only occur when starting from a stop?

  Knocks occur when starting a car because at the moment of transmission of rotation from the engine to the wheels, many components are subjected to increased loads.

• Why might a new suspension knock when starting a car?

  A new car suspension may make knocking noises when starting off due to violation of assembly rules. Often sounds are caused by loose fasteners and silent blocks being tightened in the wrong position, on a relaxed suspension (on hanging wheels).

• Why does a knocking sound appear in the transmission after an oil change?

  If, after changing the oil in the gearbox, knocks and transmission noises occur, the cause is usually insufficient lubricant, or the use of low-quality oil or oil that does not meet the manufacturer’s tolerances.