With the engine off, press the brake pedal several times until it stops and hold it in the extreme position.
Start the engine. If the amplifier is functioning flawlessly, the pedal may move a little more.
If the pedal does not go down, it is necessary to check: the vacuum hose leading from the inlet pipeline to the brake booster may be leaking. Or there is a defect in the vacuum hose check valve or in the rubber ring between the brake master cylinder and the booster. The amplifier diaphragm may be damaged.
To check the non-return valve, remove the vacuum hose near the brake booster.
It must be blown, but not sucked.
The non-return valve is only sold together with the corresponding vacuum hose.
The arrow on the valve must point towards the intake manifold.
To replace a damaged rubber ring between the main brake cylinder and the booster, the cylinder must be dismantled (see section "Removing the brake master cylinder").
A defective brake booster is replaced as a set.
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