The design and principle of operation of the vacuum brake booster and how to check it

Vacuum brake booster and everything you need to know about it

The vacuum booster is one of the integral elements of the car's braking system. Its main purpose is to increase the force transmitted from the pedal to the master cylinder.

Due to this, driving becomes easier and more comfortable, and braking is more effective.

In the article we will analyze how an amplifier works, find out what elements it consists of, and also find out whether it is possible to do without it.

Vacuum brake booster device

Structurally, the vacuum amplifier is a sealed round-shaped housing. It is installed in front of the brake pedal in the engine compartment. The main brake cylinder is located on its body. There is another type of device - a hydraulic vacuum brake booster, which is included in the hydraulic part of the drive.

Brake booster circuit diagram

The vacuum brake booster consists of the following elements:

frame
aperture (for two cameras)
follow-up valve
brake pedal pusher
brake hydraulic cylinder piston rod
return spring

The body of the device is divided by a diaphragm into two chambers: vacuum and atmospheric. The first is located on the side of the main brake cylinder, the second on the brake pedal side. Through the check valve of the amplifier, the vacuum chamber is connected to a source of vacuum (vacuum), which on cars with a gasoline engine is used by the intake manifold before supplying fuel to the cylinders.

In a diesel engine, the source of vacuum is an electric vacuum pump. Here the vacuum in the intake manifold is insignificant, so the pump is a mandatory element. The check valve of the vacuum brake booster disconnects it from the source of vacuum when the engine is stopped, as well as in cases in which the electric vacuum pump fails.

The diaphragm is connected to the piston rod of the main brake cylinder from the vacuum chamber side. Its movement ensures the movement of the piston and the injection of brake fluid to the wheel cylinders.

The atmospheric chamber in the initial position is connected to the vacuum chamber, and when the brake pedal is pressed, it is connected to the atmosphere. Communication with the atmosphere is provided by a follower valve, the movement of which occurs using a pusher.

In order to increase the braking efficiency in an emergency, the vacuum brake design can include an emergency braking system in the form of an additional electromagnetic rod drive.

How does it work?

The operating principle is based on pressure difference. The amplifier housing includes two circuits separated by a membrane. One part of the circuit is connected to the hose (where the vacuum comes from). The other end is connected to the follow-up valve. It controls the change in vacuum and adjusts the parameters.

While the car is moving or idling (when the pedal is not pressed), the diaphragm is stationary. As soon as the driver presses the brake, the vacuum is blocked by a monitoring valve. The diaphragm moves towards the brake cylinder and pushes the rod.

The latter increases this effort. If you press the pedal all the way, the hole will increase. With higher atmospheric pressure, the vacuum also increases. As a result, the pedal response becomes sharper. When the pedal is released, the diaphragm returns to its place.

The brake pads are released.

Checking the brake booster

Checking the operation of the vacuum unit yourself is not difficult. There are several fairly simple ways:

1. The engine starts to “trouble”, and after pressing the brakes it works like a clock. The thing is that during depressurization, air is sucked into the intake manifold. And this leads to a sharp mixing of air and fuel mixture entering the engine cylinders. 2.

With the engine off, pump (press) the brake pedal 5-6 times. Then press again and stop mid-stroke. Without releasing the pedal, start the engine. The pedal “failed” to the floor - the vacuum booster is working properly.

If nothing has changed after starting the engine, then you should think about replacement or repair.

3. While inspecting the surface, you noticed smudges left by brake fluid.

You should not always be confident in the operation of the vacuum brake or brakes. They, like the whole machine, want to receive attention. And the braking system especially – it never forgives mistakes.

PS 1. It is worth thinking about repairing or replacing the unit in cases where it completely or even partially does not fulfill its functions. 2. Do not forget to check the brake system in a timely manner.

MAIN DEVICE FAULTS

There are not so many types of vacuum seal failures, namely:

Loss of tightness of the pipeline through which the vacuum is supplied, or its connection points;
Failure of the check valve;
Depressurization of the working chambers of the amplifier.

The first two faults are the main ones, but the third is very rare.

It is also worth noting that in most cars the vacuum pump operates from the vacuum created in the intake manifold (the pipeline connects them together).

But on some models, the amplifier is additionally equipped with a vacuum pump to increase operating efficiency. Moreover, this element can be either mechanical (driven by a camshaft) or electrical, with its own electric motor.

But these pumps are only an auxiliary element that increases the efficiency of the amplifier. In this case, the main vacuum is still taken from the intake manifold.

In cars equipped with this unit, the pump is another component that may become unusable. In this case, the booster will continue to operate, although in some driving modes the pedal force will increase.

SIGNS OF PROBLEMS AT WORK

Malfunctions of the vacuum amplifier and the components that ensure its operation are sure to manifest themselves, and quite clearly.

If the vacuum reservoir does not function, this will be accompanied by a “stiffness” in squeezing the pedal.

If this element completely fails, it is very difficult to press the brake pedal (to verify this, it is enough to press the pedal 4-5 times with the engine not running; on the last squeeze, the resistance will be very high).

Since the vacuum is taken from the intake manifold, the loss of tightness of the vacuum booster may be accompanied by a change in engine operation during braking (although this should not happen).

Moreover, in some cases, the speed of the power plant may drop when you press the brake pedal (even to the point of stopping the unit), while in others, the speed increases.

Everything is simple here - if there is a leak in the vacuum seal, air will leak into the manifold, which affects the proportions of the air-fuel mixture, hence the change in engine operating mode.

Another obvious sign is the appearance of hissing when the pedal is depressed. The appearance of such a sound indicates the appearance of air leaks.

As for vacuum pumps, mechanical ones can make knocking noises, and constantly (the drive rod is usually to blame for this), while in electric ones the operation noise increases, and strong heating is also possible when the motor is running (here the fault usually lies in the drive motor).

Removal of VUT if repair is required

When, after diagnostics, you find that the amplifier needs repair, and you clearly know its structure, as well as all the mechanics of working with it, then you can begin to remove the device:

First you need to get a repair kit.
Read the manual of your car to know exactly the design of the VUT.
If there is upholstery in the engine compartment and a plastic lining protecting the vacuum seal, then remove them.
Under the steering shaft, we disconnect the power steering rod from the brake pedal.
Using a 17 key, unscrew the device from the brake cylinder. Next, remove the tube from the fitting so that the hose does not bend, and slightly tilt the brake cylinder forward.
We remove the brake light wire, and then use a 13mm wrench to remove the bolts to free the VUT. For successful removal, pull out the pin connecting the amplifier and pedal. Then remove the two nuts on the bracket mounting.
Now let's start repairing the vacuum seal.

It is worth understanding that if you are unable to carry out repairs yourself, it is better to entrust this matter to an experienced mechanic or simply replace it with a new device.

Instructions for replacing the vacuum brake booster

The process of replacing a vacuum seal is simple. Dismantling proceeds in the same way as when removing the system for repairs:

First, disconnect the rod from the brake pedal. That is, we remove the locking plate of the finger by hooking it with something sharp. Now we take out our finger and go under the hood.
We disconnect all the brake fluid sensor wires from the brake fluid level.
Disconnect the amplifier from the cylinder.
Unscrew the bracket nuts and remove the amplifier directly with it. If the nuts are difficult to remove, you can use WD-40.
Disconnect by unscrewing two nuts.
Now we attach the new amplifier to the bracket and reassemble it in the reverse order.

Source: http://seite1.ru/zapchasti/vakuumnyj-usilitel-tormozov-i-vsechto-nuzhno-o-nem-znat/.html

Checking the vacuum brake booster

09.04.2015

A vacuum brake booster (VBR) significantly reduces the pedal effort required to stop the vehicle. This device makes driving the most comfortable and simplest. In addition to the boost function, the vacuum brake booster ensures the safety of road users.

That is why, if the function of the amplifier is malfunctioning, it is necessary to start checking in a timely manner. On earlier car models, significant efforts had to be made in order to reduce the speed or completely stop the car.

The amplifier makes driving a vehicle more simplified and safe, as a result of which VUT has become widespread in the modern automotive industry.

Why is it necessary to check the brake system boost?

The shell of the vacuum assistant is divided into two parts by a special partition. A cylindrical brake rod passes through the housing partition. This element transmits the force acting on the brake pedal to the brake cylinder.

An important function of the mechanism in question is to ensure the safety of the driver and road users. This is the main importance of timely inspection of the device.

Amplifier malfunctions, in rare cases, adversely affect the function of the entire machine stopping system.

The malfunction is not critical for the motorist, but it is so easy to react in time and stop the vehicle in a timely manner. To avoid unforeseen circumstances, it is necessary to promptly diagnose and service the brake booster system.

Checking the brake booster is an important part of the vehicle's technical inspection, which should not be neglected. Of course, there is no need to drive the car into the garage every day for diagnostics.

A malfunction of the amplification system may be indicated by certain facts that arise during the operation of the vehicle.

After reviewing the information provided, it is easy to identify incorrect operation of the amplifier, without expensive diagnostics.

The main signs of dysfunction of the vacuum brake booster

You can check the serviceability of the amplification system without expensive equipment and special knowledge. To do this, you need to stop the engine and bleed the brake system by pressing the car's stop pedal about five to seven times. After this, you need to start the car engine, leaving your foot on the pedal.

When starting the engine, the pedal should move forward a little. Otherwise, this indicates some malfunction in the system. Under such circumstances, it is necessary to carefully inspect all conductors and the system valve for mechanical damage.

If the operation of the amplifier begins to be accompanied by extraneous sounds, then the range of diagnosed devices expands somewhat. One of the most common areas of damage is the main conductor connecting the brake booster to the car's engine manifold. In this case, it is necessary to carry out a visual diagnosis of the element.

If the hose has broken its seal, it must be replaced. Also during diagnostics, it is necessary to check the condition of all holders and tighten them, if necessary.

In addition to these damages, internal components of the system, in particular the valve, can cause a malfunction of the VUT. Due to difficult operating conditions, the rubber seals of the system wear out. In this regard, the valve becomes heavier in movement.

Sometimes, this leads to partial damage to the flexible septum. If this malfunction is detected, you can independently restore the VUT function using a repair kit. Before doing this, you need to make sure that the amplifier itself is in full working order.

Often, improper operation of the brake booster system can lead to disruption of the function of one of the engine cylinders. As a rule, most car enthusiasts explain this problem by wear of the spark plugs, forgetting about the brake assistant.

In this case, checking the amplifier is carried out in the following way:

We suppress the VUT hose so that no air passes through it. If the engine has restored smooth operation, the reason is clear.

Thus, we learned how to check the vacuum brake booster. Happy diagnostics!

Source: http://carmend.ru/shassis/stop/proverka-vakuumnogo-usilitelya-tormozov.html

How to check a vacuum brake booster: principle of operation, device

Today, the products of the automotive industry are high-tech and high-speed. Therefore, for better braking, all modern cars, both Russian and imported, use a vacuum brake booster.

The rapid productivity and productivity are explained by the fact that the improved braking system simplifies vehicle control, allowing the vehicle to stop with a slight press on the pedal. Without this unit, it is not easy to develop all the power for good braking using physical strength alone, because after some time fatigue will appear.

Thus, VUT is designed to minimize the effort required to press the brake pedal during any type of braking.

Vacuum brake booster

The operating principle of a vacuum brake booster is based on the effect of external atmospheric pressure on a discharged area. Although there is no standard device circuit and amplifier design, the operating principle remains unchanged.

There are a lot of design solutions and modifications that differ from each other in details, as well as configuration. Thus, in a number of vehicles an additional vacuum electric motor can be attached, which is responsible for the coordinated operation of the unit under various operating conditions of the engine.

If we talk about diesel power units, then the device is mandatory for them.

This node consists of five constant components:

At first glance, the vacuum seal in the engine compartment is invisible, since it is located in a monolithic block with a scientific and technical center between the pedal mechanism and the brake master cylinder. It is a chamber delimited by a diaphragm-type partition. The separated cavities are sealed and equal.

One side of the cavity is connected to the atmosphere, and the other to the exhaust manifold of the engine, where during operation a lower pressure occurs than in the atmosphere.

The atmospheric part is located closer to the pedal, and the vacuum part is located near the cylinder. In the rear atmospheric compartment on the body there is a check valve that delays the vacuum in the engine suction pipe and prevents the gasoline mixture from entering the unit. The degree of vacuum in this chamber is regulated precisely by the valve follower mechanism.

And in the front cavity, the check valve maintains constant voltage. So, the pressure of the same value presses on the partition from both sides. The valve itself is moved by a pusher connected to the brake pedal. The return spring is responsible for returning the diaphragm to its original state after braking.

When a machine requires an emergency braking system, a special electromagnetic drive is mated to the rod.

The design of the vacuum brake booster is not complicated, which makes it possible to carry out repair work yourself.

The operation of the device is carried out due to the pressure difference formed in the vacuum and atmospheric compartments. Because of this difference, the pusher is activated, which moves the GTZ piston rod. Let's take a closer look at how a vacuum brake booster works. Initially, the pressure in both chambers is the same.

Sectional view of the VUT device

The transmission of force to the pushrod and subsequent elements occurs when the driver acts on the brake pedal. After the force reaches the valve, it closes the passage between both compartments.

Then the valve again connects both chambers and a decrease in pressure occurs in the atmospheric compartment. The difference that arises is reflected in the partition, causing it to bend and lead to the movement of the piston rod in the GTZ.

When the car finishes braking, the pressure in both compartments is equalized, and the elastic partition takes its initial position.

Failure of VUT is a serious problem that can lead to fatal consequences. To avoid this, you need to carefully monitor the braking system. The slightest deviation in operation requires diagnostics. Adjusting the vacuum brake booster is not a difficult task; you can correct some deviations yourself.

Components of a vacuum brake booster

The vacuum brake booster can either partially or completely not create a vacuum. The main reason for this may be a break or depressurization of the connecting pipes of the engine manifold and amplifier.

In addition, problems can also be caused due to a violation of the integrity or loss of elasticity of the diaphragm. If there is a malfunction in the mechanism, even a beginner will notice it.

We list the main symptoms of a faulty vacuum brake booster:

when pressing the brake pedal, you need to make an effort, which should not be the case;
extraneous noise in the system. Sounds appear due to depressurization and rupture of the hose;
The VUT draws in air;
there are smudges on the “vacuum”;
wear of the seals, rupture of the diaphragm or rubber on the valves;
At idle, the engine behaves smoothly and rhythmically like a clock, this is explained by the fact that during depressurization, excess air is drawn in and mixed with the fuel mixture.

Removed faulty amplifier

For those who are wondering how to check the vacuum brake booster, we have provided several options for initially checking the system. The performance of the VUT is checked in the following ways:

The brake pedal is depressed and the engine starts. The pedal is strongly pressed; if it does not return to its previous position, it means that there are definitely problems in the unit.
The engine starts, a few minutes pass, it is turned off. Then, without straining, press the brake pedal several times. If everything is in order, then after the first pressure, the pedal is pressed, as required, all the way. This indicates that the resulting vacuum pulled in the partition, and the rod began to push, as expected, the GTZ piston. But if, during the second press on the pedal, the stroke decreases, then it means that the discharge has nowhere to come from. When no further actions are felt after the first press, it means the system is faulty.
This test method can detect air leaks in the system. When the engine is running, the pedal presses and lingers. Without releasing the brake, the engine is turned off; the pedal should be held in this position for about thirty seconds. If the pedal moves, it means that the seal is broken somewhere. The pressure in the chamber will begin to increase and the diaphragm will act on the pusher under the pressure of the return spring. When during such a test the pedal remains unchanged, it means that the VUT is working properly.
You can also check air leaks in a similar way: with the engine not running, press the pedal all the way several times, and then, while holding the pedal, start the engine. Due to temperature changes in the chambers, the pedal should move forward slightly. When this does not happen, then you need to move on to checking the hoses themselves for integrity. If, after eliminating the “air leaks”, the system continues to “triple”, then it is time to replace the amplifier with a new one.

If, after the initial check, problems are noticed, then you need to move on to a longer process - inspection of the integrity of parts.

Open the hood of the car and turn on the engine for two minutes.
Then turn it off and wait half a minute.
Press the brake pedal several times until you can hear air entering the system.
At the same time, pay attention to the VUT check valve. To do this, remove the part to be tested from the rubber flange seal.
Place a suitable rubber bulb on a small fitting, you can take it from a hydrometer.
Next, squeeze it; when the valve is in order, the rubber bulb will not release. If this happens, the valve itself should be replaced and the vacuum brake booster checked again. If nothing has changed and the problems are also noticeable, then the problem is in the system itself, which is easier to change than to repair yourself. Without the appropriate knowledge and tools, independent repairs are impossible.

If you have meters, you can test for leaks under load. To do this, start the engine, and then press the brake pedal under a force of 20 kG. Hold the pedal until the vacuum in the VUT reaches point B = 66.

7 kPa (500 mm Hg) . Then turn off the engine and check the output of the vacuum gauge - the rate of decrease in vacuum should not exceed 3.3 kPa in 15 s. When your readings are different, the amplifier needs to be repaired or replaced.

Leak test

You can also check the system with a meter and without load. To do this, start the engine, do not press the brake pedal at this time, and wait until the vacuum depth is equal to A = 66.7 kPa (500 mm Hg).

Then turn off the engine and check the vacuum gauge data. Its rate of decrease in the depth of vacuum should be no higher than 3.3 kPa in 15 seconds .

If a discrepancy is found, look for and correct the cause of the leak.

After checking for leaks, it is worth adjusting the free play of the brake pedal. Adjusting the length of the rod results in a gap that determines the degree of pressure on the brake cylinder. It is important to correctly adjust the length of the rod and set the appropriate gap. When the engine is not running, the free play of the pedal should be between 5-14 mm.

This gap is controlled by a bolt located above the VUT plane. When the gap is small, the working cylinder jams, and this leads to accelerated wear of the pads and increased fuel consumption. And also the car will begin to slow down randomly, and resemble driving on a handbrake.

On the contrary, a gap that exceeds the permissible norm indicates a violation of the tightness in the assembly and the pedal stroke will become increased.

Hydraulic pressure can also be checked with meters. When the engine is not started, the vacuum depth will be 0 mmHg. Art.

And if you press the pedal with a force of 20 kgf, then the pressure should rise to 1177 kPa (12 kgf/cm2) . Now we start the engine and wait until the vacuum depth drops to 66.7 kPa (500 mm Hg.

), then look at the parameters of the pressure gauge. Its normal value should be 6867 kPa (70 kgf/cm2) .

Simple stroke adjustment

If there are no measuring instruments at hand, then the check is carried out as follows:

Check the condition of the drive and regulator parts; there should be no gaps or oil leaks on them.
Apply the brake and check how far the adjuster piston extends. The norm is 1.7–2.3 mm. If the stroke is too high or, conversely, absent, then there are problems in the regulator.
Check the inspection plug; it should be recessed into the housing gap as far as it will go and there should be no brake fluid leaks on it. If everything is different, it means that the tightness of the sealing cuffs is broken. In such a situation, a complete replacement of the regulator is required.

Diagnosis and adjustment of the lever should be carried out frequently. When the problem is obvious, the adjustment is made as follows:

The car is parked on level ground.
The locknut of the bolt is loosened by turning it 3 turns and tightening until it connects with the tail of the regulator piston.
Tighten the bolt itself to the number of edges corresponding to your brand.
Next, tighten the nut and watch how the piston moves, its norm is 1.7–2.3 mm.
Afterwards a full check is carried out on the move in dry weather. While driving, you need to slow down until the wheels lock. If the drive adjustment is correct, then the locking of the front wheels should advance relative to the rear ones. If everything is different, then the bolt has been overtightened. It needs to be weakened by 1-2 edges and then checked again in dynamics.

Replacing the vacuum brake booster

When, after diagnostics, you find that the amplifier needs repair, and you clearly know its structure, as well as all the mechanics of working with it, then you can begin to remove the device:

First you need to get a repair kit.
Read the manual of your car to know exactly the design of the VUT.
If there is upholstery in the engine compartment and a plastic lining protecting the vacuum seal, then remove them.
Under the steering shaft, we disconnect the power steering rod from the brake pedal.
Using a 17 key, unscrew the device from the brake cylinder. Next, remove the tube from the fitting so that the hose does not bend, and slightly tilt the brake cylinder forward.
We remove the brake light wire, and then use a 13mm wrench to remove the bolts to free the VUT. For successful removal, pull out the pin connecting the amplifier and pedal. Then remove the two nuts on the bracket mounting.
Now let's start repairing the vacuum seal.

It is worth understanding that if you are unable to carry out repairs yourself, it is better to entrust this matter to an experienced mechanic or simply replace it with a new device.

Installed new VUT

Instructions for replacing the vacuum brake booster

The process of replacing a vacuum seal is simple. Dismantling proceeds in the same way as when removing the system for repairs:

First, disconnect the rod from the brake pedal. That is, we remove the locking plate of the finger by hooking it with something sharp. Now we take out our finger and go under the hood.
We disconnect all the brake fluid sensor wires from the brake fluid level.
Disconnect the amplifier from the cylinder.
Unscrew the bracket nuts and remove the amplifier directly with it. If the nuts are difficult to remove, you can use WD-40.
Disconnect by unscrewing two nuts.
Now we attach the new amplifier to the bracket and reassemble it in the reverse order.

Source: http://tbf.su/kak-vse-ustroeno/kak-proverit-vakuumnyj-usilitel-tormozov-princip-raboty-ustrojstvo

Operating principle of a vacuum brake booster

The purpose of the vacuum brake booster (VBR) is to reduce foot pressure on the brake pedal. In addition, the vacuum booster improves the effectiveness of the braking device in emergency braking mode. This ensures greater safety for the people in the car.

Problems with VUT can endanger the lives of the driver and passengers. Therefore, if you find signs of a malfunction in the vacuum brake booster, you should either repair it yourself or contact a car service center.

Vacuum brake booster device

The design of a vacuum brake booster is limited to only a few components.

It consists of the following elements:

housings;
working diaphragm;
working valve;
brake pedal pusher;
brake cylinder rod;
return spring.

The VUT body is sealed and has a round shape. Installation location: engine compartment in front of the brake pedal. The main brake hydraulic cylinder is installed on the amplifier housing.

The diaphragm is the main working part of the VUT. The material for its manufacture must be durable and elastic. The center of the diaphragm is the location of the buffer metal “penny”.

It serves to stop the rod, which continues the pedal and the cylinder. Due to the fact that the diaphragm divides the body in half, a vacuum and atmospheric chamber are formed in it. The first is directed towards the brake cylinder, the second - back.

Once the diaphragm is installed, the housing is pressurized. The working valve, which serves to connect the chambers, is actuated by the brake pedal. The vacuum chamber has a technological hole for a hose from a source that creates a vacuum.

The standby mode occurs when the operating valve opens, which is necessary to maintain low pressure in both chambers. The diaphragm returns to this state using a return spring.

How does a vacuum brake booster work? The answer is obvious if you study its structure. By pressing the brake pedal, the working valve moves to a position in which the connection between the two chambers is closed.

Further pressing leads to the opening of a special hole that connects the contents of the atmospheric chamber with the air outside.

The pressure of the air column in the Earth's atmosphere is much higher than that in the chamber. The operating principle of a vacuum brake booster is based on the difference in pressure that drives the rod. The movement of the rod makes the brakes work.

This is exactly how the VUT of a car with a gasoline engine works. The role of the source of vacuum in it is assigned to the exhaust manifold. A diesel internal combustion engine requires the installation of a vacuum pump for these purposes.

The design of vacuum pumps produced by different companies differs greatly from each other. The Ford pump is a cylinder with a membrane to create a vacuum. Amplifiers manufactured by Renault are rotating blades. However, this does not change the basic principle of operation.

Signs of a faulty vacuum brake booster

The list of VUT breakdowns is not too extensive.

Problems arise mainly due to the following reasons:

the pipeline that ensures the movement of air during vacuum or its joints has become depressurized;
the check valve has broken down;
at least one working chamber in the amplifier has become depressurized;
The vacuum pump installed on some engines has failed.

In the latter case, the amplifier will be able to continue working, but the force on the pedal will significantly increase.

To understand that there is “something wrong” with the vacuum brake booster, you don’t need to be an expert in the design of a car or show miracles of observation. Tight pedal squeeze, grinding, “triple” at idle indicate obvious problems.

There is another sure way to recognize a faulty VUT. Pump the brake pedal several times and lock it in the middle of its stroke. If it fails, the brake booster is working. If the pedal has not changed its position, the VUT needs to be repaired.

In some situations, when the pedal is pressed, there is a drop in the revolutions produced by the power plant, in others - absolutely the opposite. This indicates a specific cause of the malfunction - depressurization.

It is accompanied by air suction into the manifold, causing a sharp change in the proportions of the components that make up the fuel-air mixture. This leads to such significant changes in the operating mode of the engine. Another obvious sign of leakage is the hissing sound that accompanies pressing the pedal.

Poor pump performance is usually detected by ear. A mechanical vacuum pump may make a characteristic, constant knocking noise, which is a sign of a bad actuator rod. Malfunctions in the electric pump are accompanied by a high level of noise during operation. In this case, the drive motor is most likely to blame.

There are other signs that can help you recognize problems with your brake booster without getting under the hood of your car.

For example, when changing the operating mode of the power plant as a result of the action of the brakes, you can check the VUT by disconnecting the exhaust manifold from the pipeline. In this case, to plug the fitting, a rubber plug or a tube of suitable diameter is used, which must be clamped.

The improvised plug is firmly fixed with a clamp. After this, the engine starts briefly. If pressing the pedal is not accompanied by a change in speed, this means that the amplifier is sucking in air.

Vacuum brake booster repair

If problems are detected, their cause should be specified during the inspection of the amplifier before repair. Eliminating problems with VUT is possible only if the pipeline, as well as the check valve or its seal are damaged.

In other cases, it is better to replace the vacuum brake booster. But in order to find out which element of the VUT was damaged, a thorough check of its individual parts is required, especially for tubes and clamps.

You need to do the following:

examine the clamps and tube for cracks;
inspect the rubber sealing the VUT check valve for delamination.

Eliminating delaminations and cracks is a rather complex process. A much simpler solution to the problem is to change the clamps and pipeline. They are cheap and are always available for sale separately from other amplifier parts.

If such a replacement does not help, the VUT will have to be replaced entirely.

To change the vacuum brake booster, you need:

disconnecting the power steering rod from the brake pedal;
removing the brake master cylinder located under the hood of the car;
disconnecting the vacuum hose from the check valve;
installing a new vacuum booster in the reverse order;
checking operation by pressing the pedal when moving downhill.

If there is noise in a mechanical vacuum pump, sometimes changing the position of the rod helps - turning it 180 degrees. The electric pump, as a rule, cannot be repaired and requires replacement.

Identifying problems with the vacuum brake booster is not too difficult even for an inexperienced driver. If you have the skills, you can carry out some types of repairs on your own, but in some cases the services of a car service are required.

One way or another, you should not neglect the condition of the VUT - your safety on the highway sometimes depends on it.

Source: http://avtohomenew.ru/printsip-rabotyi-vakuumnogo-usilitelya-tormozov.html

Signs of a faulty vacuum brake booster and its repair

Today's article about checking and repairing a vacuum brake booster will be useful to many motorists.

This mechanism is designed to reduce the force that the driver has to apply when pressing the brake pedal.

Experienced car enthusiasts remember the times when they had to press the pedal hard to stop the car. However, a lot has changed since then. How to detect malfunctions of the vacuum brake booster?

Checking the brake booster - recommendations from experts

The body of the vacuum amplifier consists of two halves, between which a diaphragm is installed, through which a special rod passes. The rod itself is connected to the brake pedal, and its second end helps create pressure that drives the piston of the brake cylinder.

Information on how to check the vacuum brake booster will be very useful, because the safe operation of the car depends on it. Although the failure of this mechanism cannot lead to a complete failure of the braking system, novice drivers can be seriously frightened by even such problems in the functioning of such an important system.

Checking the vacuum brake booster is one of the stages of periodic inspection that every car owner must perform. Next, we will mention the main symptoms of a faulty vacuum brake booster and show you how to adjust and repair it.

Common breakdowns of the vacuum brake booster - diagnostics in the garage

There are several methods for such diagnostics, so we recommend using different solutions to obtain the most accurate result.

We start the engine, wait a few minutes, and turn it off. Press the brake pedal several times. If the vacuum booster is working properly, the first time you press it, you will be able to press the pedal all the way down. During further presses the stroke should be reduced. If you do not feel this difference, you can conclude that the brake booster is faulty.
Depress the brake pedal all the way and start the engine, holding it in this position. If the brake booster is working properly, the pedal should drop slightly. If the position of the brake pedal has not changed, this is another sign of a faulty vacuum brake booster.
We start the engine and press the brake pedal, hold it and turn off the engine. Without changing the position of the pedal, wait about 30 seconds. If air enters the system, pressure will begin to increase, causing the brake pedal to rise.

In some cases, the problem of system tightness can be solved using a vacuum brake booster repair kit, which includes the appropriate boots. But sometimes a complete repair of the vacuum brake booster may be necessary.

Sometimes a faulty brake booster is indicated by the fact that the engine starts to stall. As a rule, motorists do not even realize that the reason may be the appearance of excess air. To check, you need to close the vacuum booster hose to stop the air supply to the engine. If the engine eventually stops running, the problem lies in the brake system.

How to adjust the vacuum brake booster

Essentially, adjusting the brake booster is adjusting the travel of the brake pedal. To obtain optimal results, you simply need to adjust the length of the rod. To control the gap or protrusion, a special bolt is used.

It is also necessary to adjust the position of the adjusting screw, which will allow you to determine the optimal moment of operation of the atmospheric and vacuum valves.

The ability of the clutch pedal to return to its standard position depends on this indicator.

If you tighten the screw too much, the pedal will return very slowly, and overtightening it will make it quite difficult to press the pedal.

Preparation for repair of the vacuum brake booster

First of all, it is necessary to dismantle the upholstery in the engine compartment and remove the windshield trim.

To prevent air from entering the system, it is not recommended to remove the pipes that go to the brake master cylinder.

After this, unscrew the brake cylinder from the vacuum booster and carefully tilt the element forward to avoid deformation of the brake pipes. First, the hose must be disconnected from the vacuum booster fitting.

In order to dismantle the amplifier, unscrew the mounting bolts, having studied the manufacturer's recommendations in the operating instructions. Also remember to disconnect the wire going to the brake light.

At the final stage, you need to disconnect the pedal itself, for which a special pin and nuts are used. If you have a good understanding of automotive components and mechanisms, you can repair the vacuum brake booster. We advise you to first find a diagram of this device on the Internet, which will significantly facilitate the implementation of the task.

Source: http://avtopub.com/priznaki-neispravnosti-vakuumnogo-usilitelya-tormozov-i-ego-remont/