The main factor of malfunction of the vacuum brake booster is its complete or partial inability to create a vacuum in the working chamber. A potential source of the problem is an open or depressurized hose connection between the engine intake manifold and the amplifier.

Interferences in the operation of the unit are also caused by defects inside the amplifier - due to a violation of the integrity of the working surface of the diaphragm or loss of elasticity by the valve. In order to detect malfunctions of the vacuum brake booster, certain tests are carried out.

Methods and signs of detecting malfunctions of the vacuum brake booster

1. For instance. Start the engine and turn it off after a few minutes. Then press the brake pedal some times with the usual effort. With a working amplifier, at the moment of the first pressing, the pedal will be pressed, as expected, all the way. The system will work, and the created vacuum will attract the diaphragm, which helps to push the piston of the brake master cylinder through the rod.

   Further, the valve will equalize the pressure in the chamber with atmospheric. During the second and subsequent presses of the pedal, the discharge will not be taken from anywhere, which makes the pedal travel less and less. If there is no difference between the initial and further pressing on the pedal, then it is clear: this device does not provide additional force in the master brake cylinder.

2. Following the experience done, it is useful to perform another one. The engine is off. The brake pedal has been depressed several times in a row. Her move testified to something. Either the results of the experiment seemed inconclusive, or there was a desire to make a control approbation. The following actions are performed. The brake pedal is depressed and the engine starts when the pedal is depressed.

   With a working vacuum amplifier, a vacuum is formed in its vacuum chamber, due to which the membrane presses on the rod, the rod pulls the pusher connected to the pedal, and the latter is slightly lowered.

   In the case when the pedal remained in place, the conclusion is drawn: the expected chain of events did not take place due to a malfunction of the vacuum brake booster. Such checks reveal significant damage to the part.

3. Another test makes it possible to determine the presence of small air leaks. With the car engine running, press the brake pedal, then, without releasing it, turn off the engine. Hold the pedal in the same position for half a minute.

   Due to the leakage of the amplifier, the pressure in the vacuum chamber will increase. The diaphragm, under the influence of the return spring, having lost the support of the force that balances its position, will press on the pusher and raise the brake pedal.

If this is not observed, then there are no malfunctions, and the vacuum brake booster is working normally. In any case, if there is a need to repair any brake unit, it is taken into account that there may not be a second chance for repair, therefore, they turn to car service professionals for assistance in diagnostics and repairs. They can produce.

VACUUM BRAKE BOOSTER OVERVIEW

MP-BS 3151-3510010

DESCRIPTION OF THE DEVICE AND PRINCIPLE OF OPERATION OF THE STANDARD VUT

The vacuum brake booster (VUT) is one of the most common devices applied in brake system of a modern car. VUT provides a decrease in the force applied to the brake pedal, while maintaining the efficiency of the service brake system.

Before proceeding to the description and review of the design of a VUT manufactured by MetalPart, we will briefly outline the principle of operation of this unit of the vehicle brake system using the example of a standard vacuum brake booster.

The vacuum brake booster is sealed, made as a single unit with the main brake hydraulic cylinder located on it. VUT is located in the engine compartment directly in front of the brake pedal.

There are ( see fig.):

Elastic diaphragm - the main working part of the device. The diaphragm divides the VUT body into two chambers. The first - vacuum, directed towards the brake cylinder, the second, atmospheric - towards the brake pedal. In this case, the vacuum chamber communicates through the check valve with a vacuum source. In the initial position, the pressure in the chambers is equally low.

- The piston rod of the main brake cylinder - passes through the diaphragm and is connected at one end to the brake pedal, and the other to the brake cylinder piston.

- Pusher- linked to the brake pedal.

- Follower valve - closes the channel connecting the atmospheric chamber with the vacuum chamber.

- Return spring- puts the amplifier diaphragm into standby state.

Figure: 1. The device of the standard VUT

The action of the VUT is based on the creation of a pressure difference in its chambers.

The depressed brake pedal transmits force through the tappet to the follower valve, which closes the channel between the atmospheric and vacuum chambers. The movement of the valve creates a communication of the atmospheric chamber with the atmosphere through the corresponding channel, as a result of which the vacuum in the chamber drops. After overcoming the spring resistance due to the pressure difference, the diaphragm moves the piston rod of the brake cylinder.

In proportion to the force of pressing the brake pedal, additional force is generated on the piston rod of the master brake cylinder. The maximum additional effort realized with the standard VUT is related to the effort from the driver's leg with a coefficient equal to 3.5.

After releasing the brake pedal, the atmospheric chamber is connected to the vacuum chamber, the pressure in the chambers is equalized. Under the action of the return spring, the diaphragm returns to its original position, the device is again ready for operation. These are, in general terms, the device and the principle of operation of a standard VUT.

TECHNICAL CHARACTERISTICS VUT MetalPart

ADVANTAGES AND DESIGN FEATURES OF VUT MetalPart

• gain 7,0 ... The specified coefficient is achieved through the use of two vacuum chambers. VUT MetalPart provides effective braking with less effort on the brake pedal ;
• the presence of two diaphragms. A longer service life of the VUT is provided - the load on each of the diaphragms is reduced. In case of failure of one of the VUT diaphragms MetalPart continues to work in the standard VUT mode, with a gain of 3.5;
• smaller overall dimensions in comparison with the standard one. Free engine compartment space is increased;
• steel union of the non-return valve. Provides a longer service life.

ANATOMY WUT MetalPart MP-BS3151-3510010

The vacuum brake booster is delivered in a three-layer corrugated cardboard package that protects the product from mechanical damage during transportation.

To protect against corrosion, the VUT housing is made of 2 mm thick galvanized metal and painted with powder enamel.

The tightness and durability of the device is ensured by the use of 16 padlocks at the junction of the case with the lid. This type of connection excludes the "suction" of air and ensures the integrity of the VUT structure when exposed to vibration transmitted by the car body.

The photo below shows a stem follower and a polyurethane foam filter seal. This filter element provides air purification and protects the atmospheric chamber from dust and moisture.

In a vacuum booster MetalPart a durable steel check valve is installed. The photo below shows a close-up of the check valve threads with traces of the compound used to seal the connection.

Shown below is a lock washer that secures the piston follower collar securely in the seat.

Having dismantled the washer, we remove the pusher collar.

Shown below is the cuff bore with three working edges - they ensure the tightness of the vacuum chamber. This constructive solution allows to exclude the "suction" of air into the vacuum chamber and ensures the stability of the VUT MetalPart at low engine speeds.

Additional seal in the VUT cover provides a cuff with four lips that protect the follower valve body from dust and moisture ingress.

To demonstrate the main structural difference of VUT MetalPart dismantle the housing cover. In a vacuum booster MetalPart situated three cameras - two vacuum and one atmospheric. The photo below shows the diaphragm separating the atmospheric and first vacuum chambers.

The use of two vacuum chambers and two diaphragms in the VUT design made it possible to double the total usable area of \u200b\u200bthe diaphragms, which led to an increase in the VUT gain MetalPart to the value 7,0 .

In case of failure of one of the VUT diaphragms MetalPart continues to work in the standard mode, with a gain of 3.5.

This is how the cavity of the first vacuum chamber looks like:

To demonstrate the cavity of the second vacuum chamber, we dismantle the diaphragm separating the two vacuum chambers.

This overview was prepared by engineers MetalPart to clearly demonstrate the advantages of our company's vacuum amplifier.

Company MetalPart guarantees the high quality of its own products, as well as its long and flawless service, subject to the rules of installation and operation.

The vacuum booster is designed to create additional force applied to the master brake cylinder rod. The vacuum in the brake booster is created by the reduced pressure in the intake manifold.

The vacuum amplifier cannot be repaired and is replaced in the event of a malfunction. If an unusually large pedal force is required to achieve sufficient braking when the engine is running, check the brake servo.

Check vacuum amplifier carry out in the following order:

Press the brake pedal 5 - 6 times with the engine off to create the same pressure in the vacuum and atmospheric chambers of the vacuum booster, close to atmospheric (remove the vacuum);

Keeping the brake pedal depressed, start the engine;

With a working vacuum booster, the brake pedal after starting the engine should “go forward” and weaken the resistance force on the leg;

If the brake pedal does not "move forward", check the tightness of the connecting hose between the inlet and the booster or the serviceability of the vacuum booster itself.

A non-return valve may also be the cause of a malfunction of the vacuum booster. Using a screwdriver, carefully squeeze out the valve and blow in the direction of the arrow that is stamped on the valve. Purge air must exit from the other side of the valve. If you blow against the arrow stamped on the valve, then the air, on the contrary, should not come out from the other side. When installed, the valve is pressed into the brake booster.

Removal and installation of the vacuum booster without installed ABS system

Withdrawal - carry out the vacuum amplifier in the following order:

Remove the “-” wire from the AB terminal;

Remove the noise insulation located in the engine compartment of the engine;

Remove AB;

Remove the coolant expansion tank;

Disconnect the multi-pin connector for the coolant temperature display and remove the two bolts;

Unscrew two bolts and remove the right partition of the AB compartment;

Unscrew one bolt and remove the left rear AB compartment bulkhead. Set the expansion tank aside;

Disconnect the connector block on the brake fluid reservoir cap and unscrew the reservoir cap;

Using a siphon-pear, pump out the brake fluid from the reservoir and remove the master brake cylinder;

Disconnect the vacuum hose going to the brake booster;

Remove the driver's side instrument panel lower casing;

The hydraulic drive of brakes and clutches of cars contains a unit that facilitates the control of these systems - a vacuum booster. All about vacuum brake and clutch boosters, their types and designs, as well as the selection, repair and replacement of these units - read the article presented on the website.

Vacuum brake booster: stopping the car effortlessly

Braking a car sometimes requires a lot of effort on the pedal, which leads to driver fatigue and carries a potential threat - at some point, the driver simply does not have enough strength for normal braking. All these problems are solved by a special unit - a vacuum brake booster. Read about what it is, about the operation of the amplifier and its operation in this article.

The effectiveness of a vehicle's brakes is of great importance - if the braking system is not applied 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 you press the pedal.

Repair of the vacuum brake booster is necessary if the brakes become "wadded", and the pedal has to be pressed with great effort in order to brake.

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

The vacuum brake booster (abbreviated as VUT) of VAZ cars makes it easier for the driver - it enhances the effect of pressing the pedal in the braking system (TC). This assembly consists of the following main parts:

• valve;
• metal case;
• diaphragm;
• piston;
• stock;
• powerful return spring;
• a pusher that connects to the brake pedal;
• protective cover;
• flange for installing a check 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 closes the check valve installed in the VUT flange. Air (vacuum) by means of a rod and a piston when pressing the brake increases the braking effect, thereby facilitating the work of the driver - there is no need to press the pedal with great force. After releasing the pedal, 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 cars VAZ-2106-07 and VAZ-2108-10, brake boosters that are different in appearance are installed, but the principle of operation of the devices is the same. We check the serviceability of the VUT as follows: press the brake pedal and start the engine - if the pedal "falls through" (falls under the pressure of the foot), the VUT works.

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

• the "vacuum" check valve is faulty;
• there is an air leak from the hose connecting the intake manifold with the brake booster;
• there is no compression in the internal combustion engine cylinder, where the vacuum comes from.

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

The repair of the VAZ 2106, 2107, 2108, 2109, 2110 vacuum brake booster should begin with dismantling 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 easy to do. We remove the node as follows:

It is not difficult to disassemble 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 of the VAZ-2109 vacuum amplifier has a diaphragm, a cuff, a boot, covers (2 pcs.) And a valve. All parts should be changed so that later you do not have to redo the work. When assembling the vacuum amplifier, it is better to immediately fix the diaphragm to the plastic casing, so it will be easier to mount the unit.

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

Repair of the vacuum brake booster UAZ

Malfunctions of the vacuum amplifier of UAZ vehicles can be determined by the following signs:

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

If there are smudges of "brake" in the area of \u200b\u200bthe VUT, it is necessary to urgently change or repair the GTZ, but if the liquid has already entered the vacuum amplifier, most likely, the VUT will also have to be repaired.

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

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

the two lower nuts of the amplifier bracket are located in the passenger compartment, they are on a turnkey basis for 17, we turn off this fastener;

Features of the repair of UAZ vacuum amplifiers

Unlike the vacuum amplifiers of VAZ cars, the VUT body on UAZ cars is very durable, and it is not at all easy to halve it. You can bend the protrusions with a pry bar and a hammer, but this is how the work is done in violation of the technology - according to the instructions, one half must be turned relative to the other. The biggest problem during disassembly is the "halving" of the case - sometimes these parts boil so much that it is impossible to disassemble the unit. Car owners of cars advise in no case to press one body into another - then turning will definitely not work.

Another problem in the repair of "vacuum equipment" is the low quality of spare parts in the repair kit, sometimes the installed parts are not enough for six months. Motorists advise not to repair, but to buy a new spare part, although there is another disadvantage here - VUT for cars such as 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 dismantling station, which has a master brake cylinder suitable for the mountings, and install it on the car by fitting. As a result, it is cheaper and more reliable - imported parts, even in a used condition, serve for several years without any complaints.

Often, after replacing the VUT, problems appear, and the car does not slow down as much as it used to be with a working “vacuum cleaner” - the brake pedal takes over at the very end, or the system does not completely release the brake. The whole point here lies in the rod, which presses on the GTZ piston - it may not be adjusted from the factory. This stem has an adjusting screw that is secured with a locknut. On UAZ vehicles (we do not take into account the Patriot model), check the rod adjustment as follows:

Even on UAZ Hunter, the pedal can "take" at the very end, and it has a large free travel. It is necessary to pay attention to the position of the pedal - if it is too low from the floor in the passenger compartment, it must be adjusted: