Vacuum brake booster — removal and installation (Renault Symbol 2)

Tightening torques:

• Brake master cylinder nuts - 18 Nm
• Vacuum booster nuts - 23 Nm

The brake booster is not repairable. During operation, the booster air filter and check valve are replaced.

Removal

1. Disconnect and remove the battery.

2. Remove the brake master cylinder.

3. Unscrew the four bolts and one nut securing the battery protection, remove the protection.

4. Unscrew the two expansion tank mounting nuts, remove the tank and secure it to the side.

5. Disconnect the vacuum hose from the vacuum booster.

6. In the salon:

• remove the clip (A) securing the brake pedal pin to the booster rod;
• unscrew the four nuts securing the amplifier.

7. Remove the amplifier from the engine compartment.

• check the adjustment dimensions of the amplifier (Figure 7.22) and restore them if necessary.

Installation

Installation is carried out in the reverse order of removal.

Remove air from the brake system drive.

Checking the amplifier

Without starting the engine, press the brake pedal several times to remove the vacuum in the booster chamber and, holding the pedal pressed all the way down, start the engine. Simultaneously with the engine running, the brake pedal should "fall" slightly, this means that the vacuum brake booster is working properly.

If the pedal does not "fall through", you should check the booster air filter. To do this, remove the rubber cover in the rear of the booster in the passenger compartment near the brake pedal and slide the cover along the rod.





To replace the filter, it is not necessary to remove the vacuum booster: under the control pedal support, use a screwdriver or a metal hook to remove the old filter (F).

In the new filter (A), make a radial cut and put the filter on the vacuum booster rod. Put the filter in place and straighten it.

Using a screwdriver, as shown in Figure 7.23, remove the old air filter. Then, having made a cut in the new filter, install it in its proper place, making sure that it covers all the holes. Install the rubber cover and check the operation of the amplifier again.



If the result is unsatisfactory, try replacing the booster check valve. To do this, disconnect the vacuum hose from the vacuum booster. Pull out the check valve (Figure 7.24), rotating it to remove it from the rubber seal.

Blow the valve, air should flow only in one direction - from the booster side. If the valve does not blow or blows in both directions, replace it. Check the condition of the rubber seal. Assemble the unit, connect the vacuum hose and check the operation of the booster.



If the amplifier still does not work, replace it, as the company does not supply a repair kit of parts.

Checking the seal

Special devices:

• Pressure gauge and adapters - Mot. 1311-01

1. Check the condition of the seal between the master cylinder and the vacuum booster.

If there are any signs of leakage, replace the seal, see. "Master brake cylinder".

(Original article is on the portal RENAULTBOOK)



2. Install the pressure gauge Mot. 1311-01 between the vacuum booster and the intake manifold:

• a) Remove the vacuum hose.
• b) Place a technological piece of hose on the check valve nipple (1).

• c) Secure the adapter (B) from the Mot. 1311-01 kit with clamps (2).

• d) Connect the pressure gauge hose to the intake manifold fitting. The pressure gauge tap should be located on the intake manifold side. Open the tap.

3. Run the engine at idle speed for one minute.



4. Close the pressure gauge valve and turn off the engine.

5. The pressure gauge should register a vacuum of about 613 mbar. If the vacuum decreases at a rate greater than 33 mbar in 15 seconds, then there are leaks in the system (either in the check valve or in the amplifier itself). If the amplifier is leaking, replace it as an assembly.