Vacuum brake booster. Braking

Today, rarely anyone can imagine the operation of the brake system without a vacuum brake booster. Next, we will talk about malfunctions and methods for repairing the node in question. From a technological point of view, repairing a vacuum brake booster is not difficult, even if you decide to carry out the procedure yourself.

It is only recommended to take into account the design features of a particular car model, but the basic principle of the repair itself is similar for all models.

It is advisable to familiarize yourself with the device of this unit before direct repair or replacement.

Vacuum brake booster device

Structurally, the vacuum brake booster is combined with the GTZ into one unit. For a person with a developed intellect, the scheme of action of the element in question will not present any difficulties. The housing is divided into two parts, while the atmospheric part is located on the side of the brake pedal, and the vacuum part is located on the side of the main brake cylinder.

With the help of a check valve, the vacuum chamber is connected to the intake manifold, which in turn is a source of vacuum. An electric vacuum pump is often used on diesel engines to keep the vacuum booster running continuously.

When the engine is stopped, the vacuum booster is disconnected from the manifold by the action of the check valve, which is why the brake booster is only able to operate when the engine is active. In the event of a malfunction or failure of the element in question, a similar disconnection occurs.

Due to the follower valve, the atmospheric chamber in the initial position is connected to the vacuum chamber and to the atmosphere when the brake pedal is activated. A pusher is connected to the brake pedal, due to which the follower valve moves. A diaphragm is connected to the GTZ rod from the side of the vacuum chamber, it contributes to the injection of brake fluid through the piston to the working cylinders.

Due to the return spring, the diaphragm moves to its original position at the end of braking. The design of the amplifier can also have an electromagnetic drive of the rod. The active brake booster is used in the ESP system and its main purpose is to prevent rollover.

In general, the operation of the vacuum brake booster is based on the pressure difference in the atmospheric and vacuum chambers. It is due to this difference that the pusher is activated and contributes to the movement of the GTZ piston rod.

Malfunctions of the vacuum brake booster.

The first thing to focus on is that malfunctions of the node in question cannot contribute to the complete deactivation of the brake system. As a result, the control of the car becomes more difficult and the driver is forced to apply more effort by pressing the brake pedal. Traditional faults include the following:

• The presence of a malfunction inside the vacuum booster itself, for example, aging of the rubber of the valves or a diaphragm rupture. In this case, the valve will begin to poison the air.
• Breakage or depressurization of the hose, due to which the engine manifold is connected to the vacuum brake booster. In this case, you can hear the hiss of the element in question. Be sure to check the tightness of the clamps and the hose itself for breaks or cracks.

How to check the vacuum brake booster?

1. If the engine starts to triple, diagnose the serviceability of the vacuum booster. Depressurization is often accompanied by suction of air into the intake manifold pipe, therefore, the air-fuel system that enters the engine cylinder is sharply depleted.
2. As a second diagnostic option, make about five strokes with the brake pedal with the engine off. Further, in the middle of the course, fix the pedal and start the engine. If the pedal fails during starting, the vacuum booster is functioning. If it remains motionless, then it is necessary to replace or repair the vacuum brake booster.
3. During visual inspection, it is strongly recommended to pay attention to the presence of smudges that may appear on the vacuum booster housing.
4. The vacuum brake booster should be periodically adjusted.

For repair or replacement, it is necessary to prepare a standard set of tools or an appropriate kit.

Step by step repair procedure:

1. Study the car manual and decide on the key design nuances of the vacuum booster.
2. Disconnect the drive rod of the element in question from the brake pedal, which is located under the steering shaft.
3. Remove the GTZ in the engine compartment.
4. Depending on the malfunction, replace or repair this unit.

The principle of operation of the vacuum brake booster

How does a vacuum brake booster work? The solution is quite elegant and uses a resource that we have "under our feet", or more precisely - "above our heads". Remember, Ostap Bender spoke about a large column of air that presses on every person? So, he puts pressure and quite seriously on everything around. We do not notice this, due to the fact that we have internal pressure. Tires we have to inflate to create a pressure greater than atmospheric pressure. Do you remember what will happen to a tin can if the air is pumped out of it? That's right - atmospheric pressure will make a "bun" out of it. Or the Magdeburg hemispheres, which could not be torn apart by two teams of horses? The atmospheric pressure is very strong. Let's try to use it for peaceful purposes - to strengthen the brakes. You have already understood that in order to use it, and it began to act, air pressure must be removed from a certain chamber or, more simply, it must be pumped out. Or, on one side of the body, you need to create a pressure less than atmospheric pressure (this is how airplanes fly, by the way, and therefore, according to the same principle, a twisted ball flies along a curved trajectory). Otherwise, according to Newton's third law, the force of action will be equal to the force of reaction, and nothing will happen. Let us now take a sealed chamber and provide it with a membrane, dividing the chamber into 2 parts. Let's put a kind of "smart valve" in one half, which will open when we need it, connecting this half of the chamber with the atmosphere. Let's close this valve. And in the membrane we will also make a valve that will initially be open. Those. both halves will communicate freely.

The source of discharge in the vacuum booster is the engine

Now let's pump air out of the chamber. A vacuum will be created there, the same in both halves, thanks to the open valve. Nothing will happen. Now let's simultaneously close the valve between the halves of the chamber and let the atmosphere into one of the halves. It is not difficult to guess that all the force of the atmosphere will be directed to the membrane and begin to press with its inherent force of 10-odd tons (!) per square meter. The membrane will move and do the work we need due to the force of atmospheric pressure, and not our own. How cunning we are. Now it remains to attach the rod to the diaphragm and connect it to the brake master cylinder, which supplies brake fluid to the slave cylinders, which in turn move the brake pads. And on the other side of the membrane, we will attach the rod to the pedal and our atmospheric valve. And now we need very little effort to open the valves. We even have to increase it to feel the braking effort.

Now that the braking is done, it remains for us to close the atmospheric valve with the reverse movement of the pedal and open the valve connecting our halves. Will air be pumped out of the chambers again? and vacuum will be restored in the entire chamber. The system is ready to brake again! It remains to figure out how to maintain a rarefaction. An internal combustion engine consumes or even "sucks in" air to burn fuel with great voracity. Accordingly, in the intake manifold (this is the pipe through which the engine sucks in air) there will be a decent vacuum. Now let's just connect it, again, through "smart" valves, to the amplifier chamber. And when we need it, we will open the valve, and the engine itself will suck out all the air from the amplifier chamber. Elegantly? Undoubtedly. But sometimes they still install a special vacuum electric pump to eliminate uneven air intake by the manifold, especially for diesel engines, where the negative pressure is very small. What happens if we turn off the engine or turn off the vacuum pump? Recall that our membrane is connected to both the master brake cylinder and the pedal. Mechanical (kinematic) connection is not lost! Our pedal will directly move the master cylinder as before, simultaneously causing the already useless opening/closing of the corresponding valves. There will be no more amplification. Both sides of the membrane will have the same pressure, thanks to a special check valve that will turn off the vacuum line when the engine or electric pump is turned off. Yes, the effort will be significantly higher, but you can get to the service.

Scheme of the vacuum brake booster

And now that you know everything, look at the actual amplifier circuit

1 - flange of fastening of a tip; 2 - stock; 3 - diaphragm return spring; 4 - sealing ring of the master cylinder flange; 5 - the main brake cylinder; 6 - amplifier pin; 7 - amplifier housing; 8 - diaphragm; 9 - amplifier case cover; 10 - piston; 11 - protective cover of the valve body; 12 - pusher; 13 - pusher return spring; 14 - valve spring 15 - follow-up valve; 16 - stock buffer; 17 - valve body; A– vacuum chamber; IN– atmospheric chamber; C, D- channels.

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Additional safety when driving a car, in addition to the quality of the road surface, is created by a properly functioning braking system. And for such overall machines as VAZ, its work should be monitored especially carefully. The shorter the stopping distance of the car, the safer the movement will be. Reduce it, make better grip with the road surface, allows the vacuum brake booster VAZ 2110.

It is a device that ensures the normal process of braking a car by creating additional force on the brake pedal by discharging. This mechanism contributes to the smooth functioning of the braking system, while at the same time facilitating its control. This reduces machine wear and driver fatigue.

Troubleshooting the vacuum booster

Devices from different manufacturers may vary in characteristics and quality, and the price of the VAZ 2110 vacuum booster may also vary. Since the functioning of its mechanism affects the operation of other parts and assemblies, and above all the car engine, you should not save and carefully monitor its serviceability.

If a hiss is heard from under the hood, a burning smell of oil is felt in the cabin, and the brake works, like in a muffled car, only after repeated pumping of the brake pedal with your foot, then you should immediately contact a car service for diagnostics and, if necessary, replace this device.

You can test the “tens” vacuum brake booster for proper operation on your own. To do this, with the engine off, repeatedly press the brake pedal. This method checks the uniformity of pressure in the cavities. Everything is fine when the valve body does not stick.

Then, when you hold your foot on the brake pedal, the engine starts. If the pedal is moved forward simultaneously with the foot, then the amplifier is operational. Otherwise, you need to make sure that the malfunction lies precisely in it, and not in a problem with the tip flange or its fastening.

Still uncoordinated functioning of the pedal is possible due to a faulty connection of the fitting on the engine exhaust pipe to the hose. This all also has a detrimental effect on the performance of the braking system and its efficiency.

Troubleshooting

When the identified signs indicate a malfunction of the VAZ 2110 vacuum brake booster, you can try to provide first aid to your car on your own. In normal condition, the braking system should hold it in place when tilted 25º to the horizontal. If she does not cope well, it is worth loosening the lock nut and tightening the cable.

Then you need to check the full lever stroke, it is necessary that it be approximately 2-4 teeth. Having tightened the locknut tightly, it is worth performing a series of safety braking while simultaneously controlling the stroke of the lever. Moreover, the rotation of the wheels with the lever lowered to the end should be free, without effort. If such a test reveals the inability of the amplifier to cope with braking, this indicates the need to replace it.

Many car services provide such a relevant service today as tuning the VAZ 2110 brake system, the price of the unit in case of replacement is still higher than its improvement. It also affects the rear brake discs, in addition to the amplifier, the modernization of which is the installation of a special washer. This seemingly insignificant detail can significantly affect the operation of the amplifier and the braking process as a whole.

When the driver presses the brake pedal, the rod passing through the washer begins to exert pressure on the brake master cylinder. Because of this, the operation of the bypass valves begins a little later. Thus, installing a washer makes braking smoother, the pedal is softer, and its reaction in the event of a sudden stop does not change.

But if a hiss has already appeared, the engine stalls from pressing the brake pedal, or it has become very tight, it is necessary to replace the mechanism. Otherwise, driving such a car becomes unsafe for yourself and others. In preparation for replacing this assembly, disassembly of the rear of the engine compartment is required, removal of the elastic seal, upholstery and jabot.

The process begins by disconnecting the pad wiring from the sensor showing the brake fluid level. Supporting the check valve, disconnect the hose from the amplifier. Next, unscrew both fixing nuts of the master cylinder of the braking system. It is smoothly turned away from the amplifier to the distance required to extract the latter, and this is done without removing the brake pipes.

Under the instrument panel located in the passenger compartment, all four fixing nuts of the brake pedal bracket should be unscrewed, which is rather difficult due to their inconvenient location. Then the wires, the bracket and the amplifier itself are removed in the engine compartment at the same time as the brake pedal assembly.

Having disconnected the two fixing nuts, remove the lock plate of the fastening pin with a screwdriver and, pushing it out, separate the booster pusher from the pedal. Having unscrewed the damaged amplifier from the pedal assembly, a new one is placed in its place. Moreover, it is necessary to monitor the correctness of its location: the pedal should be at the bottom, and the hose fitting should be at the top. After that, all operations performed earlier are performed in the opposite order to removal.

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.

The effectiveness of the car's brakes is of great importance - if the brake system does not work effectively, an accident can occur. In order for the brakes to be clear, an amplifier is installed on all modern cars, it provides an instant stop of the vehicle when the pedal is pressed.

Repair of the vacuum brake booster is necessary if the brakes become "cottony", and you have to press the pedal with great effort to brake.

Repair of the vacuum brake booster VAZ 2106, 2107, 2108, 2109, 2110

The vacuum brake booster (abbreviated as VUT) of VAZ vehicles facilitates the work of the driver - it enhances the effect of pressing the pedal in the brake system (TS). This assembly consists of the following main parts:

• valve;
• metal case;
• diaphragms;
• piston
• stock;
• powerful return spring;
• pusher, which is connected to the brake pedal;
• protective cover;
• flange for installing a non-return valve.

The body of the device is divided by a diaphragm into two halves, and from the side where the vacuum is created, the main brake cylinder is installed. A vacuum (vacuum) is created by connecting this part of the body to the intake manifold of the internal combustion engine, and when the engine is not running, the channel is blocked by a check valve installed in the VUT flange. Air (vacuum) with the help of a rod and a piston, when the brake is pressed, enhances the braking effect, thereby facilitating the work of the driver - there is no need to press the pedal with great force. After the pedal is released, a powerful return spring allows the diaphragm inside the body to return to its original position. When the engine is turned off, no vacuum is created in the system and the vacuum brake booster does not work.

On VAZ-2106-07 and VAZ-2108-10 cars, brake boosters of different appearance are installed, but the principle of operation of the devices is the same. We check the serviceability of the VUT as follows: we press the brake pedal and start the engine - if the pedal “falls through” (falls under foot pressure), the VUT works.

The main problem with the vacuum booster is damage to the diaphragm. When the diaphragm has ruptures, air penetrates from the outer part of the housing into the vacuum cavity, and no vacuum is created in the device. But not necessarily the malfunction may lie in the device itself - often the VUT does not work due to air leakage or for other reasons:

• defective check valve "vacuum";
• there is an air leak from the hose connecting the intake manifold to the brake booster;
• there is no compression in the ICE cylinder where the vacuum comes from.

It should be noted that the vacuum brake booster on VAZ 2106-10 vehicles is connected by a hose to the fourth engine cylinder.

Repair of the vacuum brake booster VAZ 2106, 2107, 2108, 2109, 2110 should begin with the dismantling of this unit, then the VUT must be disassembled.

VUT on a VAZ-classic car is removed quite simply, and if you have minimal locksmith skills, this work is not difficult to do. Remove the node as follows:

It is not difficult to disassemble the VUT 2108-2109, but for disassembly it is necessary to fix the device. We disassemble the node in the following order:

Usually, the repair kit for the VAZ-2109 vacuum booster has a diaphragm, a cuff, anther, covers (2 pcs.) And a valve. All the details should be changed so that later you do not have to redo the work. When assembling a vacuum booster, it is better to immediately fix the diaphragm on a plastic casing, so it will be easier to mount the assembly.

Which side the spring is placed on does not matter, but when assembling the amplifier, you will have to make an effort to get the holes in the housing onto the studs.

UAZ brake booster repair

Problems with the vacuum booster of UAZ vehicles can be identified by the following signs:

• the engine troit, and since on the "UAZ" engines the vacuum hose goes to the manifold of the first cylinder, if the VUT is faulty, this particular cylinder does not finish;
• a hiss is heard under the hood - the diaphragm poisons the air;
• the brake pedal is hard and does not squeeze when starting the engine;
• there are wet smudges between the GTZ and the amplifier (brake fluid flows).

If “brake” smudges are found in the VUT area, it is urgent to change or repair the GTZ, but if the liquid has already entered the vacuum booster, it is likely that the VUT will also have to be repaired.

Another common malfunction in the brake system is the failure of the check valve. This simple mechanism is very easy to check - you need to blow into it. The valve should be blown freely in one direction (when rarefied air is supplied from the manifold), and in the opposite direction the air goes with great difficulty. If the valve is defective, it is blown freely in both directions.

The amplifier is removed on cars manufactured by the Ulyanovsk Automobile Plant according to the same principle as on VAZ cars. Consider the replacement of VUT using the example of a UAZ-31519 car:

the two lower nuts of the amplifier bracket are located in the passenger compartment, they are turnkey 17, we unscrew this fastener;

Features of the repair of UAZ vacuum boosters

Unlike the vacuum boosters of VAZ cars, on UAZ cars, the VUT body is very durable, and it is not at all easy to split it in half. You can bend the protrusions with a mount and a hammer, but this is how the work is done in violation of the technology - according to the instructions, one half must be rotated relative to the other. The biggest problem during disassembly is the "halfing" of the case - sometimes these parts boil so much that it is impossible to disassemble the assembly. Car owners advise not to press one body into another in any case - then turning will definitely not work.

Another problem in the repair of "vacuum trucks" is the low quality of spare parts in the repair kit, sometimes the installed parts are not enough for half a year. Motorists advise not to repair, but to buy a new spare part, although there is another minus here - VUT for cars like UAZ-469 or UAZ-452 is not cheap, about 3 thousand rubles. Alternatively, you can pick up a “vacuum” from a foreign car at a car disassembly, in which the main brake cylinder fits on the mounts, and install it on the car by fitting. As a result, it turns out cheaper and more reliable - imported parts, even in used condition, last for several years without any complaints.

Often, after replacing the VUT, problems appear, and the car no longer slows down as it was before with a working “vacuum” - the brake pedal takes at the very end, or the system is not completely released. The whole point here is the rod that presses the GTZ piston - it may not be adjusted from the factory. This stem has an adjusting screw, which is fixed with a lock nut. On UAZ vehicles (we do not take into account the Patriot model), we check the stem adjustment as follows:

Even on the UAZ Hunter, the pedal can “take” at the very end, and it gets a lot of free play. It is necessary to pay attention to the position of the pedal - if it is too low from the floor in the cabin, it must be adjusted: