Brake booster

The brake booster cannot be repaired. Only the following may be serviced:

• the air filter,
• the check valve.

REMOVAL

Disconnect and remove the battery.

Remove:

• the master cylinder (follow the method described previously),
• the battery protection plate (4 screws, 1 nut),
• the two mounting nuts of the expansion reservoir, and move it towards the engine.

Disconnect the flexible vacuum hose from the brake booster.

Inside the passenger compartment:

• remove the pin (A) from the clevis connecting the brake pedal to the pushrod by releasing the clip,

• remove the 4 mounting nuts of the brake booster,
• remove the brake booster.

INSTALLATION

Before refitting, check:

• dimension L = 104.8 mm,
• dimension X = 22.3 mm.

Refit in reverse order of removal.

Bleed the brake circuit.

Petrol engine

LEAK TEST

When carrying out a leak test on the brake booster, make sure there is a perfect seal between it and the master cylinder. If there is a leak at this point, replace the seal (A).

The brake booster leak check must be carried out on the vehicle, with the hydraulic circuit in working order.

Connect the vacuum pump between the brake booster and the vacuum source (intake manifold) using a "T" fitting and the shortest possible hose.

Run the engine at idle for one minute.

Clamp the hose (clamp Mot. 453-01) between the "T" fitting and the vacuum source.

Stop the engine.

If the vacuum drops by more than 33 mbar (25 mmHg) in 15 seconds, there is a leak that may be located either:

• at the check valve (replace it),
• at the pushrod diaphragm (in this case, replace the brake booster).

If the brake booster is not working, the braking system still functions, but the pedal effort required to achieve equivalent deceleration is much greater than with power-assisted brakes.