Most modern cars are equipped with a hydraulic brake system. It is complemented by a vacuum booster. This mechanism increases the effort placed on the pedal by the driver several times. In other words, it is much easier to slow down with a vacuum cleaner. However, like any other mechanism, an amplifier can malfunction. In today's article, we will consider what the vacuum brake booster is designed for, how to test it, and what is its principle of operation.
Device
The design of this element requires the following details:
- Aperture
- Atmospheric channel.
- Pusher.
- Stock.
- Vacuum channel.
- Piston and return spring.
How does it work?
The principle of operation is based on the 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 connects to the follower valve. It controls the change of vacuum and adjusts the parameters.
When the car is moving or at idle (when the pedal is not pressed), the diaphragm 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 also increases this effort. If you press the pedal all the way, the hole will increase. At higher atmospheric pressure, the vacuum also increases. As a result, the response to the pedal becomes sharper. When you release the pedal, the diaphragm returns to its place. The brake pads are unclenched.
How to check? Method number 1
There are several diagnostic methods for this element. All of them will be considered in our article. So, how to check the valve of the vacuum brake booster with your own hands? You can diagnose the device without removing it from the installation location.
So, the engine starts and after 10 or more seconds of operation we turn it off. Next, press the pedal with the usual effort until it stops. If the element is serviceable, the system will operate once and the vacuum will attract the diaphragm spring. With subsequent clicks, the pressure in the system will be excised. The pedal will be less and less. But it is important for us to provide braking force exactly at the first press. If the device has completed the test, it is in working condition. An important point: the pedal at the subsequent start (if it is clamped in the floor) should lower. This indicates that sufficient pressure has accumulated in the system. Both circuits are working.
Method number 2
This verification method is as follows. It is necessary to start the engine and press the pedal. After that, turn off the engine. At the same time, we hold the pedal in the floor without releasing it. After 20-30 seconds we release it. The mechanism should return to its original position, since excessive pressure has formed in the circuit. If the pedal "failed", this indicates a leak in the vacuum chamber.
It is necessary to repair or replace the vacuum brake booster. The price of the new item is about a thousand rubles. For foreign cars of the Mitsubishi Lancer type, this figure is several times higher (3-4 thousand). Therefore, it is sometimes advisable to repair a vacuum brake booster. Below we will look at how to do this.
Vacuum Brake Booster Repair: What Fails?
Often when the “vacuum cleaner” breaks down, the diaphragm fails. If there are gaps from the outside of the housing, air enters the vacuum cavity. Because of this, the system does not produce the desired vacuum.
But also the check valve of the amplifier fails. Damage can also consist in a banal "suction" of air. Because of this, the vacuum brake booster also does not work. How to check it? When the engine is running, it will make a characteristic hissing sound. Choke occurs due to poorly twisted clamps or leaking pipes. Least of all, the amplifier does not work due to 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 box.
Dismantling
Replace failed elements in place will not work. It is necessary to remove the vacuum brake booster. VAZ of classic models (including Samara) is equipped with this element near the motor shield. So, open the hood, disconnect the amplifier from the brake master cylinder. An important point - the tubes remain in place. If you remove them, the system will be airy.
There is nothing fatal in this, but you will have to re-pump the brakes (and this is extra time). Therefore, we simply take the cylinder with the tubes to the side. Remove the hose from the check valve. In the passenger compartment, we remove the bracket, which fixes the brake pedal. So we will release the pusher "vacuum cleaner". After that, it remains only to unscrew the 4 fastening nuts of the amplifier itself in the engine compartment and get it out.
Dismantling and repair
Next we need a vise. We clamp the amplifier in a vice and bend the mounting grooves of the two “halves”. This is done with a minus screwdriver. On the last rivet, try to hold the outside of the case. Since there is a spring inside it, it can fire when the case is parsed. Then we remove two rubber covers and a plastic casing with a pusher from the mounts.
Now we take out the parts from the repair kit and set them in place of the old ones. Repair kit includes the following elements:
- Aperture.
- Cuffs.
- 2 covers.
- Anthers.
- Valve.
Having installed new parts, we collect back the vacuum brake booster. How to check it, we already know. When assembling, you must immediately attach the diaphragm to the plastic casing. The spring can be installed on either side. However, when assembling the case, you need to make an effort to get it on the studs.
We assemble in the reverse order. Before starting, carry out a visual inspection. All hoses and clamps must fit snugly and be firmly fixed. If the motor is troit, it means that air is leaking. One of the hoses may have been damaged.
So, we found out what a vacuum brake booster is, how to check it and repair it with our own hands.