Vacuum brake booster: how to check? Car maintenance

Most modern carsare equipped with hydraulic brake system. It is supplemented by a vacuum amplifier. This mechanism increases the force imposed by the driver on the pedal several times. In other words, it is much easier to brake with a vacuum cleaner. However, like any other mechanism, the amplifier can malfunction. In today's article, we will look at how the vacuum brake booster is arranged, how to test it and what its operating principle is.

Device

The design of this element assumes the following details:

• Diaphragms.
• Atmospheric channel.
• Pusher.
• Stock.
• The vacuum channel.
• Piston and return spring.

How does it work?

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

When the vehicle is moving or idling(when the pedal is not pressed), the aperture is stationary. As soon as the driver presses the brake, the discharge is blocked by a follow-up valve. The diaphragm moves towards the brake cylinder and pushes the rod. The latter and increases this effort. If you press the pedal against the stop, the hole will increase. At greater atmospheric pressure, the discharge increases. As a result, the response to the pedal becomes sharper. When the pedal is released, the diaphragm returns to its place. The brake pads are released.

How to check? Method number 1

There are several methods for diagnosing thiselement. All of them will be considered in our article. So, how to check the valve of the vacuum brake amplifier by yourself? You can diagnose the device without removing it from the installation place.

So, start the engine and after 10 or moreseconds of work muffle it. Then press the pedal with the usual effort until it stops. If the element is working, the system will work once and the vacuum will pull the diaphragm spring. At subsequent pressures, the pressure in the system will be dissipated. The pedal will progress less and less. But it is important for us to provide the braking force at the first push. If the device has coped with the test, it is in working order. Important point: the pedal on the next start (if it is clamped in the floor) should go down. This indicates that the system has accumulated enough pressure. Both circuits are serviceable.

Method No. 2

This method of verification is as follows. You need to start the engine and press the pedal. Then stop the engine. In this case, the pedal is held in the floor, not releasing it. After 20-30 seconds, release it. The mechanism must return to its original position, because excessive pressure was generated in the circuit. If the pedal "failed", this indicates a leak in the vacuum chamber.

It is required to repair or replace the vacuumbrake booster. The price of the new element is about a thousand rubles. For foreign cars such as Mitsubishi Lancer, this figure is several times larger (3-4 thousand). Therefore, repair of the vacuum amplifier of brakes is sometimes expedient. Below we will consider how to do this.

Repair of the vacuum brake booster: what goes wrong?

Often with breakage of the "vacuum cleaner", the diaphragm breaks down. In the presence of ruptures from the outside of the housing, air enters the vacuum cavity. Because of this, the system does not provide the required discharge.

But the check valve also failsamplifier. Breakage can be and in the banal "suction" of air. Because of this, too, does not work the vacuum brake booster. How to test it? When the engine is running, it will emit a characteristic hissing sound. The sucker arises because of poorly twisted clamps or leaky nozzles. The lowest power amplifier does not work because of the lack of compression in the cylinder. The vacuum hose is connected to the fourth cylinder. If the compression in it is below 9 points, there may be problems with the vacuum cleaner.

Dismantling

Replace failed components in placeit will turn out. It is necessary to remove the vacuum brake booster. VAZ classic models (including the "Samara") is equipped with this element near the engine board. So, open the hood, turn off the amplifier from the main brake cylinder. The important thing is that the tubes stay in place. If they are removed, the system will be airborne.

There is nothing fatal about this, but you will have toto carry out repeated pumping of brakes (and this additional time). So just take the cylinder with the tubes aside. Remove the hose from the non-return valve. In the cabin we dismantle the bracket, which fixes the brake pedal. So we will release the pusher "vacuum cleaner". After that, it remains only to unscrew the 4 fixing nuts of the amplifier itself in the engine compartment and get it out.

Disassembly and repair

Next, we will need a vise. Clamp the amplifier in a vice and bend the grooves of fixing the two "halves". This is done with a minus screwdriver. On the last rivet, try to hold the outer part of the case. Since there is a spring inside it, when the case is analyzed, it can shoot. Further we remove from fastenings two rubber covers and a plastic casing with a pusher.

Now we remove the parts from the repair kit and install them in place of the old ones. The repair kit includes the following elements:

• Diaphragm.
• Cuffs.
• 2 cases.
• Anthers.
• Valve.

Having installed new parts, we collect it backthe vacuum amplifier of brakes. How to test it, we already know. When assembling, the diaphragm must immediately be fastened to the plastic casing. The spring can be installed by either side. However, when assembling the body, you need to make efforts to get it on the studs.

Assemble in the reverse order. Before starting, make a visual inspection. All hoses and clamps must be snug and securely fastened. If the motor is moving, then the air is sucked. Perhaps one of the hoses has been damaged.

So, we found out what a vacuum brake booster is, how to test it and repair it yourself.

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