The performance of the brakes is also affected by the condition of the tyres, the vehicle load and the alignment of the front wheels.
Checking the operation of the vacuum booster
Release the existing vacuum with the engine off by depressing the brake pedal several times at 5 second intervals. Fully depressing the brake pedal, start the engine. Make sure the clearance between the brake pedal and the floor panel decreases as the vacuum in the engine stabilizes.
Connect the vacuum pump directly to the brake booster.
Operate the vacuum pump several times.
Check that the vacuum does not decrease by more than 33 mbar in 15 seconds.
If so, then there is a leak either:
- through the check valve gasket, in this case replace the gasket;
- through the diaphragm of the pusher, in this case, replace the amplifier.
Leak test
Start the engine and let it idle for about 1 minute. Shut it off by applying vacuum to the booster. Press the brake pedal several times with normal force and release the existing vacuum. Make sure that the gap between the brake pedal and the floor panel gradually increases as the brake pedal is depressed. Start the engine. Press and hold the brake pedal, then stop the engine. Hold the pedal down for about 30 seconds or more and check that the pedal travel does not change.