The appearance of extraneous sounds during the trip is always a wake-up call for any car owner. When there is a knock in the car while driving, it can not be ignored, as this often indicates critical wear of the components or impending failure of important systems. The nature of the sound, its frequency, and its dependence on speed or load help pinpoint the source of the problem.
In this article we will discuss in detail the main causes of knocking, methods of their independent diagnosis and professional elimination. You will learn how to distinguish a harmless sound from a symptom of a serious breakdown, and what steps you need to take immediately to avoid costly repairs.
Diagnostics on the nature of sound and traffic conditions
Primary diagnostics begins with careful listening to the car in different modes of operation. The nature of the knock It can be deaf, tolling, metallic or soft, and each indicates a different malfunction. For example, a thud often indicates wear of rubber metal hinges, whereas a ringing sound indicates the presence of backlash in metal joints.
It is important to pay attention to when exactly the sound appears: when accelerating, braking, on the bumps or when turning the steering wheel. If the knocking gets worse as speed increases, the problem may lie in the wheels or transmission elements. Constant rhythmic sound is often associated with rotating details.
⚠️ Warning: If the knocking is accompanied by vibration of the steering wheel or loss of controllability, further movement at high speed can be dangerous. It is recommended to slow down and perform a visual inspection immediately.
For accurate determination of the source, the masters often use a stethoscope or a long screwdriver, applying it to different nodes. Localization of sound It allows you to weed out false noises coming from the cabin or from the road surface. Do not rely only on hearing, as the body of the car works as a resonator, distorting the real location of the breakdown.
Knocks in the front suspension: levers, racks and steering
The most common cause of noise is wear of elements. front-suspension. Road conditions contribute to the rapid failure of the Silentblocks, ball supports and stabilizer racks. Knocking in this case usually manifests itself when passing irregularities, pits or "lying policemen".
Particular attention should be paid to ball-propTheir destruction can lead to the separation of the wheel with all the ensuing consequences. Checking is carried out by swaying the wheel in the vertical and horizontal planes with the car raised. The luft in the joint of the hinge will clearly indicate the need for replacement.
- 🔧 Stabilizer struts: emit a characteristic ringing knock on small irregularities and with a distortion of the body.
- 🔧 Silentblocks of leverage: give a deaf sound when abrupt start or braking, as well as at the joints of the asphalt.
- 🔧 Steering tips: knocking when turning the steering wheel on the spot or in motion, often accompanied by backlash.
Diagnosis of shock absorber racks is also important, since a broken shock absorber not only knocks, but also stops extinguishing the fluctuations. This leads to accelerated wear of other parts of the suspension and deterioration of brake dynamics. Visual inspection for oil leaks will help to quickly identify the defect.
☑️ Checking the front suspension
Noise in the rear suspension and chassis
A knock at the back of a car while driving often goes unnoticed until it turns into a crash. In the dependent suspension (beam) most often wear the sleeves of the stabilizer and the Silent blocks of fixing the beam to the body. In independent suspension, the list of potential culprits is expanded by levers and additional hinges.
An important element is shock absorber And his bearing. Wear of the upper mount of the shock absorber often causes knocking, which is transmitted to the body and is perceived as noise in the cabin. The check is carried out by rocking the car: if it swings more than 2-3 times, the shock absorber is faulty.
⚠️ Attention: Knocking in the rear suspension can be caused not only by wear, but also by weakening of the fasteners. Regular stretching of threaded connections is a mandatory maintenance procedure.
It is also worth checking the condition. brake calipers. If the calipers guides are worn or lubricated, the brake pad may dangle and make unpleasant sounds when moving. This is easy to check by trying to stagger the shoe through the caliper technology window.
Why is the beam banging?
In the rear beam, the seats of Silentblocks are often broken. The metal begins to beat against the metal, causing a strong knock. Solution: replacement of the Silentblocks or bushings, sometimes you need to replace the beam itself.
Engine knock and gearbox: critical malfunctions
Knocking in the engine while driving is the most dangerous symptom that requires immediate stop. It may indicate problems with crank-and-shifter. The knock of root or rod liners has a deaf metallic hue and often depends on the frequency of rotation of the crankshaft.
In automatic and mechanical gearboxes, knocking can occur due to wear of the bearings of the shafts or gears. If the knock in the gearbox disappears when the clutch is squeezed (on the mechanics), the problem is most likely in the primary shaft or bearings. In automatics, a hum and a knock may indicate problems with the hydraulic transformer.
To diagnose the engine, the method of listening with a stethoscope at different points of the cylinder block is used. Tsokot valves less dangerous but unpleasant sound, which indicates the need to adjust the thermal gaps or malfunction of hydraulic compensators.
Use a long wooden stick or hose as a stethoscope. Put one end to your ear and drive the other on the engine, and you will hear the sound source much more clearly than just the ear.
Transmission, actuators and wheels
In front-wheel drive cars, a frequent cause of knocking are hinges of equal angular velocities (SRUS). The external SRUS usually crunches or knocks when cornering, especially when accelerating. The internal SRUS can give vibration and knock when accelerating on a straight road.
Wheel problems can also create the illusion of knocking in the suspension. Deformation of the disc, a hernia on the tire or uneven wear of the tread cause a beat that is transmitted to the body. Ballancing wheels helps eliminate vibrations, but won’t fix geometric defects.
In all-wheel drive cars, the source of noise can be drive-shaft Or the center differential. Lufts in the crosses of the driveshaft cause a characteristic metal clang when starting movement or changing gears.
Comparative table of sounds and malfunctions
To simplify the diagnosis, we have compiled a table that will help to compare the audible sound with the probable cause. Remember that an accurate diagnosis can only be made by a qualified specialist after dismantling the node.
| Type of sound | When it comes to | Probable cause | Danger. |
|---|---|---|---|
| Deaf knock | On the rocks, the pits. | Silent blocks, stabilizer bushings | Medium |
| Calling clanging | When you turn the steering wheel | Steering tips, traction. | Tall. |
| Metal thumping | When accelerating under load | Engine liners | Critical |
| Crunch/crackle | In a gas turn | Outside SRUSS | Tall. |
| Hum/wag | Constantly growing at speed. | Stack bearing | Tall. |
Timely diagnosis of knocking allows you to eliminate the problem at an early stage, preventing a chain reaction of destruction of adjacent components of the car.
Remediation and prevention
Elimination of knocking depends on the cause identified. In most cases, it is required replacementRepairing rubber elements or restoring the geometry of metal arms is often not economically feasible. The use of original spare parts or quality analogues guarantees a long life.
Prevention includes regular inspection of the chassis, especially after the winter season and travel on bad roads. Timely lubrication of hinges (if the design provides maintenance) and the replacement of anthers prolong the life of the nodes. Ignoring the slightest knock in the engine may lead to the need for major repairs or replacement of the unit.
Do not forget about the driving culture: the careful passage of irregularities and the absence of sharp starts from the spot significantly reduce the load on the suspension and transmission. Regular maintenance is not only an oil change, but also a comprehensive check of all vehicle systems.
Why does the car only knock on the cold?
Knocking on a cold engine is often associated with heat gaps. Metal parts expand when heated and gaps decrease. If the knocking disappears after warming up, this may indicate wear of the piston group or the need to adjust the valves. However, in the suspension, the cold also plays a role: rubber elements tan in the cold and knock harder until they are warmed up from friction.
Can I drive if the suspension is knocking?
You can drive, but very carefully and not for long. A knock is a signal that there is a backlash. Luft leads to the destruction of neighboring parts. For example, a broken ball finger can fly out at any time, which will result in loss of control. It is better to reach the service at low speed, avoiding sharp maneuvers.
How to distinguish the thud of a shrus from a hub bearing?
A hub bearing usually hums or howls, and this sound varies depending on the speed, but not on the position of the wheels. The SRUS crunches or clicks specifically when turning the wheels and applying gas. The internal SRUS can give vibration to the floor during acceleration.
Does the pressure in the tires affect the appearance of knocks?
Yes, it does. Too low pressure makes the sidewall of the tire soft, and when passing irregularities, a characteristic slap or knock can occur. The pumped tire makes the suspension tougher, transferring all the blows to the body, which can be perceived as frequent blows.