The vacuum brake booster reduces the force applied to the brake pedal, thereby making driving easier. The principle of operation of the vacuum brake booster is based on the use of vacuum in the intake manifold. When the vacuum booster fails, the brake system does not work, but it is necessary to apply much more effort to press the brake pedal.
Press the brake pedal several times with the engine off to create the same pressure in the cavities of the vacuum booster, close to atmospheric. At the same time, by the force applied to the pedal, determine if the valve body is sticking. Stop the brake pedal in the middle of its travel and start the engine. With a working vacuum booster, the brake pedal should move forward after starting the engine.
If the pedal does not move forward, remove the vacuum hose from the brake booster and start the engine. Close the end of the hose with your finger and check if there is a vacuum in the hose.
If there is no vacuum, check the tightness of the vacuum hose and replace if necessary.
On a diesel engine, disconnect the vacuum hose from the vacuum pump and check for vacuum at the pump nozzle. The vacuum pump on a four-cylinder engine is flange-mounted to the rear of the cylinder block, while on a six-cylinder engine it is located on the side of the left cylinder head.
If there is no vacuum, replace the vacuum pump.
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