MOT No. 30
The engine must be off.
Press the brake pedal 10 times.
Keep the brake pedal now fully depressed and start the engine.
With a working brake booster, the pedal should move a little at this moment. If this does not happen, then the brake booster is faulty.
Most likely, you should look for a malfunction in the vacuum system: a leaky vacuum hose from the intake manifold to the brake booster, faulty check valve in the vacuum hose near the booster, a rubber ring between the brake master cylinder and the booster, or the booster membrane.
To check the non-return valve, disconnect the vacuum hose from the brake booster.
Blowdown should be possible, but not suction.
The non-return valve can only be purchased together with the corresponding vacuum hose.
To replace a damaged rubber ring between the brake master cylinder and the booster, the cylinder must be dismantled.
A faulty brake booster cannot be repaired. Replace.
Removing the brake booster
Remove the brake master cylinder.
Remove vacuum hose.
Remove the shelf on the left under the dashboard, as well as the air duct (chapter «Salon»).
Remove the pivot pin in the head of the brake booster control yoke.
Unscrew the self-locking nuts securing the brake booster in the passenger compartment.
Then remove both nuts securing the brake booster in the engine compartment.
The distance between the center of the fork head hole and the four stud bearing surface must be 230 mm (tolerance 0.5 mm).
After adjustment, tighten the locknut thoroughly.
Lubricate pivot bolt with grease prior to installation.
Use only new hinge pin retainer and new self-locking nuts. Install a new O-ring between the brake booster and master cylinder.
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