Causes of car vibration that occurs at certain speeds. Vibrations - what are they? Engine vibration at idle. Balancing - eliminating imbalance of a part

If you encounter a vibration problem when accelerating, we advise you to immediately look for the cause of the problem. Our article will help you with this. We'll list the most common causes of severe vibration during overclocking and help you figure out how to fix the problem.

Main reasons

In most cases, vibration is the result of centrifugal forces. They can occur for the following reasons:

• Significant imbalance of the main components and rotating components of the motor. This applies to the crankshaft and clutch. You can find the exact cause using diagnostics at the service.
• Significant difference in the weight of the elements of the crank mechanism (pistons and connecting rods).
• Imbalance of brake system elements and wheels.

Increased body vibration - typical causes

There are various factors that can cause your car body to shake excessively. All of them can be divided into three groups:

1. Constructive. These are factors caused by the design characteristics of a particular element of the vehicle. For example, tires are inflated through a valve, the presence of which negatively affects the balance of the wheels.
2. Operational. As a rule, the essence of the problem lies in uneven wear of an element, a change in its shape or characteristics. Vibration is often caused by excessively worn, damaged or defective engine mounts. They are used to reduce the vibration that the power unit transmits to the car body. As a rule, pillows are made of metal with a rubber layer.
3. Technological. In this case, the vibration is caused by deviations in the imbalance parameters and dimensions of parts that contribute to their interchangeability. In practice, it happens that the mass of the purchased connecting rod does not correspond to the required value, as a result of which the motor experiences an uneven load. This is what leads to vibration of the car at idle, during acceleration and driving.

We are looking for a solution to the problem

In fact, we have listed the most common causes of car vibration that appears during acceleration. It's time to deal with the problem. First of all, we will talk about balancing. Although it is almost impossible to completely get rid of engine vibration, you can reduce it as much as possible.

Before balancing, a power unit element or other car part must be inspected by a specialist. With the help of special equipment, the master can determine the heaviest side. After this, you can either reduce its weight or increase the weight of the opposite part. In fact, it is better to entrust such procedures to an experienced specialist, since it can be difficult to balance the crankshaft or even the wheels yourself.

Basic balancing methods

Today, in most cases, two main methods of balancing parts are used:

• static balancing;
• dynamic balancing.

Each method has certain features, which will be discussed below.

Static balancing method

This balancing is carried out without rotating the part. The advantage of this method is that it can be used in a regular garage, since no special devices are needed. True, getting rid of imbalances with static blocking alone can be difficult.

The essence of the method is that the element is mounted on bearings or prisms. After this, the part must be rotated around its axis, as a result of which it will be in a position in which the heavier part is lower than the rotation axis. Remember that the bearing resistance should be as low as possible and the prism should be positioned as horizontally as possible.

Dynamic balancing method

To implement this method, the part is constantly rotated on appropriate equipment. The advantage of dynamic balancing is that it helps to completely eliminate imbalances. This method is usually used even for the most rigid elements, for example, the cardan and crankshaft. Since all work is carried out using a computer, you will be able to get the most accurate information about the changes.

The application of dynamic balancing of the clutch basket, brake drum, crankshaft and wheel hub involves reducing the weight of the heavier part by removing a certain amount of material. For this they use different ways processing, such as drilling.

Finding the source of vibration yourself

Determining the cause of shaking without special equipment is very difficult. Some drivers perceive it normally extraneous sounds when the car is moving, while others pay attention to even minimal vibration during acceleration.

The following factors may indicate the existence of the problem under discussion:

• spontaneous movement of various objects located on the front panel;
• blurry reflection in the rearview mirror (in the cabin);
• constant vibration of the steering wheel (as a rule, you need to balance the wheels of the front axle);
• vibration of the lower body and controls.

What should you pay attention to first?

First check the condition of the engine and exhaust system fasteners. The check should be carried out with the engine turned on and off. Damage to the engine mounts is considered unacceptable. Even if there are cracks, the part should be replaced. In some cases, vibration and other extraneous sounds are caused by too small a distance between the motor protection and the sump.

Make sure all threaded connections are carefully tightened. If one of the bolts is loose, you need to tighten it thoroughly. Sometimes vibration is caused by damage to the radiator fan. You can dismantle this element and check how the engine works without it.

The next stage is the gradual dismantling of attachments and determination of vibration when starting the engine and its operation. As a rule, the problem is solved by replacing the drive belt or balancing the pulley.

Another diagnostic method is to check the clutch basket and flywheel. We depress the clutch pedal completely, start the car, having previously engaged 1st gear, wait a few seconds and move the gearshift lever to the neutral position. Then you need to remove your foot from the pedal. If the vibration does not disappear, the problem lies in the basket or flywheel.

Causes of vibration while driving

In such cases, it is necessary to diagnose the gearbox and chassis of the car. If vehicle vibration directly depends on driving speed, its source may be one of the nodes located after the transmission driven shaft. Often the “culprits” of the problem are drive shafts, hubs, cardans, transfer case parts and wheels. If you feel vibration only when braking, you need to check the condition of the brake drums and discs.

Sometimes shaking is caused by installing tires that are too hard. As a result, the front axle wheels experience excessive load when braking. If vibration is felt at minimum speed, it is necessary to balance the rims. As a rule, shaking is accompanied by beating of the steering wheel.

In order to understand whether vibration during acceleration is actually caused by an imbalance of the front wheels, you can simply swap them with the wheels of the rear axle. True, thorough diagnostics using special equipment would be much more advisable. The technician will install the appropriate weights. Only at the stand can you achieve the desired result, so saving on this is not advisable.

conclusions

So, we tried together to figure out the main faults that lead to vibration of the body or engine when accelerating. Now you can carry out diagnostics yourself or go to specialists. In any case, do not forget that serious shaking is a significant problem, and therefore we do not recommend ignoring such difficulties.

If vibration of the car occurs in the body during acceleration, while driving, or even at idle speed, it is very important to quickly begin searching for the cause. IN otherwise everything can end in an accident or failure of one of the expensive engine components.

Don't forget about safety precautions! If you decide to check the condition of individual engine parts with your own hands, you need to understand that they are often hot, so you can get serious burns.

As a rule, it occurs under the influence of centrifugal forces caused by:

Imbalance of rotating components - engine crankshaft and flywheel, radiator and heater fans, clutch, driveshafts, brake discs and drums, wheels and tires;

A large difference in the masses of moving parts - pistons and connecting rods of the engine.

Causes of imbalance:

Structural - due to the design features of the part. For example, to inflate a tire, there is a valve on the wheel rim, the mass of which disturbs their balance; - technological - associated with permissible deviations in dimensions and parameters (including imbalance) of parts, ensuring their interchangeability, that is, simplifying the manufacture and repair of components. But sometimes unbalance of parts balanced separately - operational - uneven wear of the part, its deformation, defects in vibration isolators, etc.

Vibration isolator is a unit fastening element (cushion, support) that reduces transmitted vibration. As a rule, it consists of metal elements (reinforcement) separated by a rubber mass. There may be other designs - hydraulic, spring, combined.

Eliminate vibration

Balancing - It is difficult to completely eliminate shaking, but reducing it to a reasonable minimum is possible.

To do this, balance the part: - find its “heavy” side; - determine the amount of mass causing imbalance; - lighten the “heavy” side or, conversely, make the opposite side heavier.

Basic balancing methods

Static - without forced rotation of the part. The method does not require complex equipment, is available in “garage” conditions, but does not completely eliminate the imbalance. Gives acceptable results for short parts with a relatively large diameter (engine flywheel, clutch disc, etc.). They are balanced: - “on knives” (prisms) or in “bearings”. The part self-aligns, rotating around its axis, and eventually takes a position in which the “heavy” side is below the axis of rotation. The prisms must be strictly horizontal, and the bearings must have minimal resistance; - “on a support” or “on a suspension”. The “heavy” side outweighs, and the part deviates from the horizontal. As a rule, the first method is more accurate, but is only applicable to parts with cylindrical supporting surfaces.

Dynamic method - with constant forced rotation of the part using special equipment. Eliminates all components of imbalance and is applicable for rigid parts of any size (propeller shaft, crankshaft, etc.).

Determination of the amount of mass needed to eliminate the imbalance during static balancing is often carried out experimentally, and during dynamic balancing it is usually given by the computer of the balancing stand. When lightening the “heavy” side of the part, part of the material is removed from it (by drilling or other mechanical processing). This is how crankshafts, flywheels, cast iron brake drums, clutch baskets, wheel hubs, drive pulleys, etc. are balanced. When weighting the “light” side of the part, weights are attached to it (as a rule, on leaf springs or secured by welding or glue). This is done with parts for which it is impossible to remove excess material from the “heavy” side without reducing their strength. For example, with wheels and brake drums made of light alloy, driveshafts, and driven clutch discs.

Determining the source of increased vibration Without special instruments, it is impossible to correctly determine the excess of the permissible vibration level. Each person perceives it subjectively.

Vibration is noticeable in the steering wheel with a light touch of your fingers;

Objects lying on the instrument panel (“dashboard”) move;

The image in the interior rearview mirror is blurred; in a car while driving, in addition, unpleasant vibrations are felt from the controls, floor, and seats.

Before searching for the source of increased vibration, it is advisable to determine the conditions and modes of its manifestation - on a stationary vehicle (in place) or in motion. Then understand when it appeared - it was originally on a new machine, it arose during operation or after the repair of a unit. In any case, it is useful to first make sure that the engine settings are correct. The unevenness of its operation is also manifested by vibration, but this may be a consequence of defects in the ignition, power supply or injection control systems. Moreover, interruptions in the engine sometimes occur not only at idle and, in addition, can be a consequence of the installation of defective parts.

It is more convenient to identify the source of increased vibration with an assistant. One person is inside the car, the second one monitors the operation of the units from the outside.

When diagnosing a car, you should follow safety measures: - when probing “suspicious” places with your hand while the engine is running, do not touch very hot (exhaust manifold, hoses and pipelines of the cooling system) or rotating (fan impeller, driveshaft) parts;

When hanging the machine, place it on reliable supports;

When driving on public roads, do not interfere with other road users.

Vibration in a stationary vehicle usually occurs when:

Operation of the engine and its attachments (generator, air conditioning compressor, etc.);

Turning on the radiator and heater fans;

Defects in the suspension of the power unit and exhaust system.

When searching for the source of vibration, you can follow the following sequence of actions: - inspect (preferably first with the engine turned off, then with the engine running) the power unit suspensions, exhaust system and parts around them. The suspension elements must be intact. Sometimes the power guard is too close to the engine sump. Their contact also causes vibrations. Faulty parts must be replaced; - check the tightness of the tightening threaded connections, tighten the weakened; - to make sure that the vibration is coming from the fan, you need to turn it off or remove the impeller; - turn off sequentially attachments(remove the drive belts) and, starting the engine, check the vibration level throughout its entire operating speed range. A faulty unit must be replaced or its element (pulley) must be balanced; - depress the clutch pedal with the engine running or set the automatic transmission selector lever to the “N” position. If the vibration remains, its main sources may be: the flywheel, the clutch basket, the torque converter or automatic transmission parts, the crankshaft, or the difference in the weight of the pistons and connecting rods that exceeds the permissible limit.

Vibration when driving a car usually arises from parts of the transmission or chassis. If its level depends only on the speed of the car and does not change when coasting, it means that some component is vibrating after the driven shaft of the gearbox (cardan or drive shafts, transfer case parts, wheels, hubs, etc.). Moreover, the vibration frequency from the cardan is approximately four times higher than from the wheels, brake drums and discs. When vibration occurs only during braking, the most likely source is the brake rotors or drums. They, as well as hubs, can be manufactured with unacceptable deviations in the runout of the working and mating surfaces. If the tires are of poor quality, the reasons may lie in their uneven hardness, which increases with increasing load on the front wheels during braking. Shaking of the car in a narrow speed range of about 10-15 km/h is usually caused by wheel imbalance. In the front ones, it is additionally manifested by steering wheel beating. To verify the defect, you can swap the rear and front wheels or remove them and check the balancing.

In other cases it is necessary:

Hang up the drive wheels one by one; - start and warm up the engine, engage the highest (fourth or fifth) gear, slowly release the clutch pedal and increase engine speed until noticeable vibration occurs.

If there was no vibration when both drive wheels were suspended, it is most likely caused by parts of the driven axle - the hub or brake drum (disc). This can only be determined by re-checking them after replacing them one by one with obviously good ones, for example from another car. The cause of vibration on one side of the machine may be unbalance of the brake drum (disc), hub or drive parts - axle shaft or drive shaft. In this case, you will have to sequentially remove the wheel and brake drum (disc), then replace the axle shaft and hub with tested and serviceable ones, and repeat the check each time. Vibration on a new car occurs from improper installation of vibration source units or installation of components with increased level vibrations

It is necessary to look for the cause while the machine is stationary and in motion. Moreover, during inspection, you need to pay attention to the correct use of vibration isolators. They may look almost identical in appearance, but differ in characteristics for some vehicle configuration options. Therefore, it is useful to compare, at least, the markings of the parts and the hardness of the rubber (to the touch). For inexpensive cars, this should be one of the main factors when making a purchase decision, since eliminating the imbalance is not cheap, and the wear rate of the components increases significantly. During the operation of the machine until its components and engine are repaired, the vibration level changes slightly. However, over time, the initial parameters of vibration isolators deteriorate, and the comfort of the car gradually decreases. Rubber defects (aging, hardening, cracks) are usually revealed during inspection.

If vibration suddenly appears while driving, it is advisable to recall previous events in memory. For example: - immediately after intense braking, when the temperature of the parts was high, I had to drive through a deep puddle.

The reason for vibration the next time you press the pedal may be a brake disc that has warped due to sudden cooling by water;

The car hit the curb with its driveshaft when exiting the roadway or the wheel ran over an obstacle or the edge of a hole

The start of shaking indicates damage to the relevant parts (shaft, tire, wheel).

Vibration that occurs after repairs with the replacement of rotating parts indicates a large imbalance of new elements or errors during repair operations, leading to incorrect assembly of the unit or deformation of the part. For example, engine pistons and connecting rods must be selected based on weight, as a rule, with the following difference in weight: for pistons - 2.5-5 g, for connecting rods - no more than 5-10 g.

When parts causing increased vibration are easily accessible, they can simply be replaced with conditioned parts or removed for repair. Otherwise, you will have to make a decision based on the magnitude of fluctuations and the complexity of the work. Sometimes you can wait until a scheduled overhaul of the unit. If a complex mechanism (for example, an engine) has already been disassembled and new parts are installed in it or old ones are repaired by surfacing (welding), it is necessary to check their balancing before final assembly. Otherwise, you will have to rebuild the unit later.

Quite often, an imbalance appears after repairing (disassembling) the driveshaft or removing it to dismantle the gearbox or transfer case. It is therefore useful to first note the relative position of all components and work carefully, avoiding strong deforming impacts (preferably on the press). Sometimes cardan joints, for example rear-wheel drive VAZs, have locking rings of crosspieces of varying thickness. Their incorrect installation also leads to imbalance. When the vibration level is satisfactory and replacement or machining of rotating parts is not planned, it is also useful to note their relative positions before disassembling.

Possible reason increased vibrations There may also be a deviation in the geometric parameters (mainly runout) of new parts. Therefore, it is useful to check them and, based on the results of the check, exchange or try to balance them.