The vacuum brake booster is an integral part of the vehicle's braking system. In the common people, this type of amplifier is commonly called "vacuum".
It is designed to create additional reinforcement of the brake pedal, this is due to the discharge. Thanks to this type of brake booster, the functioning of the automotive brake system is greatly facilitated.
How is a brake vacuum booster arranged?
The vacuum booster of the brake system is a metal case, it is mechanically, as well as structurally connected to the GTZ, they are integral parts of one brake system. The amplifier body has two parts, into which the diaphragm divides it:
- The first part of the amplifier is vacuum, it is located on the side of the main brake cylinder.
- The second part is atmospheric, it refers directly to the brake pedal.
The vacuum-type brake booster, together with the GTZ, has the following components:
- Main body.
- follow-up valve.
- Diaphragm.
- Pusher.
- return spring.
- GTZ piston rod.
How does a vacuum unit work?
The vacuum chamber, which does not contain air, goes to the intake manifold, this is done using a special valve. Usually on modern cars, these include models no older than 2010, an electric pump is additionally installed, it is responsible for the stable operation of the vacuum booster.
At a time when the car's engine is not running, this special valve disconnects the brake booster from the manifold. Thus, when the engine is turned off, the brakes of the vehicle disappear for a while, cease to function. The same principle also works during the operation of the motor, even if the vacuum device is slightly damaged.
The second part of the vacuum unit, which can be called atmospheric, as we noted earlier, is connected to the second vacuum half with a valve. The operation of this valve is the basis for the functioning of the vacuum unit, since it creates different pressures between the two chambers of this braking device. When the engine is not running, and the driver does not press the brake pedal, the pressure in these two chambers - vacuum and atmospheric, will be the same.
When the driver just starts to press the pedal, the pusher moves along a specific trajectory, namely, to the servo valve, as well as the brake cylinder rod. With this movement, the valve closes the channel between the two parts of the unit that perform different functions.
In such a situation, in the vacuum part of the device, the pressure remains at the same level, and at that moment a vacuum occurs in the atmospheric chamber. When the braking process is completed, the spring will return the diaphragm to its original position.
What are the signs of a bad vacuum booster?
If the driver's vacuum brake booster suddenly stops working, there is no need to worry, there is a way out. You just need to apply a little more force on the brake pedal, and also control the vehicle with little effort.
You should seriously think about the complete replacement or detailed repair of the vacuum unit only in situations where it has partially or completely lost its functions.
Damage signs:
- The driver exerts more and more effort to depress the brake pedal, but the braking becomes weaker with each depress.
- If, during idle operation of the engine, it starts to "troit", while pressing the brake pedal, it works normally, keeps the desired rhythm.
- If a hose breaks or a crack has formed in it, this is usually accompanied by a loud hiss or other extraneous sounds that are uncharacteristic of the normal operation of the vehicle.
- During operation, the vacuum unit began to suck in air, even in a small volume.
- If a diaphragm rupture occurs, the rubber on the valves or seals is completely worn out.
Checking the vacuum booster
The brake system must always be in good working order, the safety of both the driver and his passengers depends on this. That is why it is worth being very sensitive to any changes in the functioning of the vehicle's braking system.
You should be alerted by clicks, crackling, grinding and other extraneous sounds. There are also other signs of a broken vacuum that an experienced driver will never ignore. Any driver, before setting off on a journey, especially a long-distance one, can independently verify that the vacuum cleaner is in good condition, even a beginner in the auto business can carry out such a check.
If the brake pedal is too hard, it is most likely caused by a vacuum in the intake manifold or a bad hose. It can also be caused by a defect in the vacuum booster itself or the control valve with which it is equipped.
How to check?
- If your vehicle's engine is "throttling" but it only happens before you apply the brakes? This is usually caused by depressurization, in which air is sucked into the intake manifold. There is a sharp mixing of air with the fuel mixture, which enters the engine cylinders.
- Turn off the engine of your car, press the pedal five to six times in a row. On the seventh application of the brakes, stop in the middle of the stroke. Do not release the pedal, start the engine at the same time. If at this moment the pedal falls to the floor, the unit is working. If the brake pedal does not change its position when starting the engine, it must be replaced or repaired.
- If, when inspecting your car, you notice smudges that the brake fluid leaves, it is also worth contacting a car service.
Be careful and check the brake system of your car from time to time. Like any part of the machine, its operation requires control, brake failure is very dangerous, so you should carefully monitor their performance.
Modern products of today's automotive industry are high-tech and high-speed. Separately, it is worth mentioning the power of cars, which, after their acceleration, are not so easy to stop. Therefore, all of them are equipped with a modern brake system, and to simplify its control by the driver, the majority of vehicles have such a unit as a vacuum brake booster.
This is the most important element for a car, which is designed not only to increase comfort when driving a vehicle, but also makes the braking system itself more efficient, allowing it to develop full power by lightly pressing the brake pedal, which is necessary to effectively stop even the most powerful vehicle. It is not easy to do this with the physical strength of the driver alone, and after several kilometers of driving, the driver of a vehicle without a VUT would feel very tired, which would certainly become an obstacle to trouble-free driving.
How is the brake booster
The device of the vacuum brake booster is not difficult, which, if necessary, allows for repair work on their own. In the body of this node are its components:
- diaphragm;
- return spring;
- pusher;
- tracking valve;
- stock.
In the engine compartment, it is invisible, since it is located in the same housing as the brake cylinder. The diaphragm delimits the body of this node into two equal halves. Both halves are sealed, and the one that is turned to the brake cylinder is airless, i.e. vacuum. The second has a message with the environment, and bears the corresponding name - atmospheric. The vacuum chamber has a special valve, thanks to which it mates with a source of vacuum. Its role is played by the area located in the intake manifold.
In a number of cars, a vacuum electric motor can be additionally installed, which will ensure guaranteed operation of the device under different engine operating conditions. It is mandatory installed on all diesel power units. The atmospheric chamber includes a follower valve, and with its help it can communicate either with the atmosphere or with the vacuum chamber. The return spring ensures that the diaphragm returns to its original position after braking is complete. If the car provides for an emergency braking system, a special drive is installed on the stem.
How this node works
The principle of operation of the vacuum brake booster is to create and maintain different pressures between the vacuum and atmospheric parts of this unit. In the standard position of the brake pedal, the pressure in the chambers is identical, but when it is pressed, the follower valve comes into play - it blocks the communication between both parts of the unit, and the vacuum in the vacuum chamber increases and drops in the next one.
Despite the opposition of the spring, the diaphragm moves forward, forcing the rod of the master brake cylinder to move. The operation of the vacuum brake booster guarantees a significant force transmitted to the master cylinder rod. At the same time, it always corresponds to the force with which the pedal is pressed, that is, if the pedal is pressed only slightly, the device will not develop full power, giving the brake system high power.
What are the problems you may face while using
Like any other node in a car, a vacuum booster requires periodic attention from a motorist. Periodically, the amplifier should be checked in order to detect a malfunction in time and take measures to eliminate it. The test starts with the engine off. Press the brake several times in a row, then fix it in the depressed position for a while. Then the pedal is released and the engine starts. Learn more about video verification:
In the event that when you press the pedal, special efforts on the part of the driver are not required, everything is in order. The difficulty of this action indicates a malfunction of the vacuum brake booster. Among the most common are the following:
- violation of the integrity of the diaphragm itself;
- problems with the hoses leading to this node;
- failure of the spring that returns the diaphragm to its original position.
It is more expedient to carry out repairs in technical centers, where specialists have a set of professional equipment at hand. Otherwise, it is better to remove it and replace it with a new unit.
Amplifier Self Test
In the event that the vacuum unit is faulty, the driver needs to exert too much effort for normal braking, which quickly tires him. Therefore, it is important to pay attention to the impending breakdown in a timely manner. Symptoms of a device malfunction can be quite diverse.
Dismantling the vacuum booster
The procedure for dismantling and installing a new unit is not so difficult, therefore, if you have free time and desire, it may well be done independently - this will save a decent amount. All work is carried out on a cold engine.
In order not to lead to the need to replace this important unit in the car, it is recommended to periodically check the condition of all connecting hoses and carry out an elementary self-diagnosis of the brake system.
The vacuum brake booster is the most common type of booster that is used in the brake system of a modern car. It creates additional force on the brake pedal due to vacuum. The use of an amplifier greatly facilitates the work of the car's braking system, and thereby reduces driver fatigue.
Structurally, the vacuum booster forms a single unit with the main brake cylinder and includes a housing, a diaphragm, a follower valve, a pusher, a piston rod of the main brake cylinder, and a return spring.
The amplifier body is divided by a diaphragm into two chambers. The chamber facing the master brake cylinder is called the vacuum chamber. The chamber opposite to it (on the side of the brake pedal) is atmospheric.
The vacuum chamber is connected to a vacuum source through a check valve. The area in the engine intake manifold after the throttle valve is usually used as a source of vacuum. To ensure uninterrupted operation of the vacuum booster in all operating modes of the vehicle, a vacuum electric pump can be used as a source of discharge. On diesel engines, where the vacuum in the intake manifold is negligible, the use of a vacuum pump is mandatory. The non-return valve disconnects the vacuum booster and the vacuum source when the engine stops, as well as when the vacuum pump fails.
Atmospheric chamber with a follower valve has a connection:
- in the initial position - with a vacuum chamber;
- with the brake pedal depressed - with the atmosphere.
The pusher provides movement of the follower valve. It is connected to the brake pedal.
From the side of the vacuum chamber, the diaphragm is connected to the piston rod of the main brake cylinder. The movement of the diaphragm moves the piston and pumps brake fluid to the wheel cylinders.
The return spring at the end of braking moves the diaphragm to its original position.
For effective braking in an emergency, the emergency braking system, which is an additional electromagnetic drive of the rod, can be included in the design of the vacuum brake booster.
A further development of the vacuum brake booster is the so-called. active brake booster. It ensures the operation of the amplifier in certain cases and, therefore, pressure build-up without the participation of the driver. The active brake booster is used in the ESP system to prevent rollover and eliminate oversteer.
The principle of operation of the vacuum brake booster is based on creating a pressure difference in the vacuum and atmospheric chambers. In the initial position, the pressure in both chambers is the same and equal to the pressure created by the vacuum source.
When the brake pedal is pressed, the force is transmitted through the pusher to the follower valve. The valve closes the channel connecting the atmospheric chamber with the vacuum chamber. With further movement of the valve, the atmospheric chamber is connected to the atmosphere through the corresponding channel. The vacuum in the atmospheric chamber is reduced. The pressure difference acts on the diaphragm and, overcoming the force of the spring, moves the piston rod of the master brake cylinder.
The design of the vacuum booster provides an additional force on the piston rod of the master brake cylinder proportional to the force of pressing the brake pedal. In other words, the harder the driver presses the pedal, the more efficient the amplifier will work.
At the end of braking, the atmospheric chamber reconnects with the vacuum chamber, the pressure in the chambers equalizes. The diaphragm moves to its original position under the action of the return spring.
The maximum additional force realized with the help of the vacuum brake booster is usually 3-5 times greater than the force from the driver's foot. A further increase in the amount of additional effort is achieved by increasing the number of chambers of the vacuum amplifier, as well as increasing the size of the diaphragm.
Until relatively recently, in order to stop one of the old models of cars, it was necessary to apply considerable effort to the brake pedal, and after some time a vacuum brake booster appeared in the device of the cars. This device greatly facilitates driving, but, nevertheless, it requires periodic repairs and monitoring of its technical condition.
Vacuum brake booster device - schematic overview
The vacuum brake booster device is inextricably linked with the master cylinder. Its basis is a body divided by a diaphragm into two chambers. The vacuum chamber is located on the side of the master cylinder, where it is connected to the intake manifold using a special check valve. It is in this area that the vacuum is created. The atmospheric chamber is located on the side of the brake pedal and, using a follower valve, is connected in turn to the vacuum chamber or to the atmosphere.
The valve itself is moved by a pusher, and the brake fluid is injected into the working cylinders by means of a piston. At the end of braking, the return spring drives the diaphragm, returning it to its original position. Some models of amplifiers can be equipped with an electromagnetic drive of the rod, which acts as an emergency braking system.
The principle of operation of the vacuum brake booster and symptoms of malfunction
The main principle of operation of the vacuum brake booster is based on the pressure difference formed in the vacuum and atmospheric chamber. It is this difference that affects the pusher, which moves the piston rod of the main cylinder of the system. In order to maintain the vacuum at the proper level, a check valve of the vacuum brake booster is used.
In the rarefied atmosphere mode, air is sucked out of the amplifier through this valve, but it no longer flows back through it.
Particular attention when checking the brake system should be paid to the technical condition of the vacuum booster. Although its malfunctions do not cause catastrophic consequences, nevertheless, the brake pedal that requires increased effort creates discomfort and makes driving difficult. There are, of course, malfunctions that still require repair or even replacement of the device.
First of all, the vacuum brake booster hose connecting it to the manifold may be depressurized or broken. After a hiss is heard, the condition of the hose itself and the quality of tightening the clamps are checked. In addition, a torn diaphragm or old rubber in the valves, through which air can also escape, is a common cause.
Vacuum brake booster - how to get to the breakdown?
In order to accurately determine the malfunction, it is necessary to carefully study the operating instructions for the car, which describes the specific model of the vacuum booster. Sometimes the reason is quite simple, when the engine starts to triple due to the suction of excess air and the depletion of the working mixture. When conducting a visual inspection, it is necessary to identify leaks on the amplifier case and be sure to find out the causes of their occurrence.
Effective repair of the vacuum booster requires a repair kit that matches the specific model and a standard set of tools. Most often, a complete replacement of the device with a new one, installed as an assembly, is performed. In order to start repair or replacement, the drive rod located in the passenger compartment is disconnected near the steering shaft on the brake pedal. After that, in the engine compartment, you need to disconnect the brake master cylinder. At the end, the vacuum hose is removed from the check valve. Now the amplifier is open for access, you can repair or replace it.
It is difficult to imagine the operation of the brakes without a vacuum brake booster. It is difficult to overestimate the work of this device, however, like all others, it is “not immune” from breakage. Today I propose to talk about the main malfunctions of the vacuum brake booster and how to fix them.
On the one hand, repairing a vacuum brake booster is not particularly difficult if you decide to repair this device yourself. The most important thing is to take into account all the design features of a particular brand of car, the very principle of repair is no different.
A little about the device of the vacuum brake booster.
Structurally, the vacuum brake booster is a single unit, combined with the GTZ. For an advanced motorist, the device of this unit will not seem complicated. The housing is divided into two parts: the vacuum part is located on the side of the main brake cylinder, the atmospheric part is located on the side of the brake pedal.
The vacuum chamber is connected to the intake manifold with a check valve, which is a source of vacuum. Most often, a vacuum electric pump is used in diesel engines in order to ensure that the operation of the vacuum booster is constant. In the event of an engine stop, the vacuum booster is disconnected from the manifold by means of a check valve, which is why the vacuum brake booster is very dependent on the operation of the motor and can only function when the engine is running.
After the brake pedal is activated by means of a follower valve, the atmospheric chamber is connected to the vacuum chamber and the atmosphere. The brake pedal is connected to the pusher, due to which the follower valve moves. The diaphragm is connected to the GTZ rod from the side of the vacuum chamber, thanks to which the brake fluid is pumped by the piston to the working cylinders.
The return spring returns the diaphragm to its original position after the end of braking. The design of the amplifier may also contain an electromagnetic drive rod. The ESP system uses an active brake booster, its main purpose is to prevent rollover.
Possible malfunctions of the vacuum brake booster.
First of all, attention should be focused on the inefficient operation of the braking system, that is, the deterioration of vehicle control (TC), the need to exert more effort in order to brake. The following faults are considered classic:
1. Malfunctions inside the vacuum booster itself (diaphragm rupture or valve rubber aging). In this case, the valve will poison the air.
2. Depressurization or complete breakage of the hose that connects the engine manifold to the vacuum brake booster. As a rule, such a malfunction is accompanied by a hiss of this device. Be sure to check the tightness of the clamps, as well as the hose for cracks and breaks.
How to check the vacuum brake booster yourself?
1. If the motor began to work unevenly (intermittently or troit), it is necessary to diagnose the serviceability of the vacuum booster. Often, depressurization is accompanied by air being sucked into the air intake manifold pipe, as a result, the air-fuel mixture entering the cylinders is sharply depleted.
2. Alternatively, you can try to diagnose a malfunction in this way: make 5-6 strokes with the brake pedal with the engine “switched off”. After that, in the middle of the stroke, lock the pedal, then start the engine. If the pedal fails during start-up, the vacuum booster can be considered working. If the pedal remains motionless, repair or complete replacement of the vacuum brake booster is necessary.
3. Conduct a visual inspection, and carefully look at whether there are any smudges on the vacuum booster housing.
Repair of the vacuum brake booster.
In order to repair or replace, you need to have some skills and knowledge, it will not be superfluous to look into the repair and maintenance manual for your car. In addition, you will need tools, usually a standard set is enough.
Below I give you a step-by-step instruction on the procedure for repairing a vacuum brake booster:
1. Read the manual (manual) for the repair and operation of the car in detail, determine for yourself the key nuances.
2. Disconnect the booster drive linkage from the brake pedal, which is located under the steering shaft.
3. In the engine compartment, remove the GTZ.
4. Depending on the breakdown, repair or completely replace this device.
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