Vacuum Brake Booster: Testing and Inspection

Power brake booster, checking for leakage and/or correct operation

Special tools:
999 5843 VACUUM PUMP AT 999 5843 Vacuum Pump AT

1. Checking power brake booster for leakage

Connect vacuum pump




Ignition off.
Remove the engine splashguard. Remove the vacuum hose from the intake manifold by pressing down the retaining clip.
Connect vacuum pump 999 5843 VACUUM PUMP AT 999 5843 Vacuum Pump AT to the hose with an adapter and clip.

Testing power brake booster
Apply a vacuum to the power brake booster and note the reading of the meter.
If the vacuum drops, there is a leak.
Remove the vacuum pump from the hose.
Depress the brake pedal a few times so that there is no residual vacuum in the power brake booster.

Inspecting non return valve
Remove the engine cover, if necessary.
Remove the vacuum hose with the non return valve.
Inspect the non return valve and sealing ring. Replace if damaged.

Note! The non return valve is only to be replaced with hose.


Note! If neither the sealing ring nor the non return valve are damaged, the leak must be in the power brake booster itself. The booster must then be replaced. See Power brake booster in LHD-models, replacement, L.H.D Removal and Replacement or Power brake booster in RHD-models, replacement on how to do this.

Connecting power brake booster

Install
- the vacuum hose to the power brake booster.
- the vacuum hose to the intake manifold with the retaining clip; check the retaining clip, replacing it if necessary.
- the engine cover.

2. Checking correct operation of the power brake booster






Caution! Always check the power brake booster and vacuum hose for leaks first.

Depress the brake pedal several times, so that there is no residual vacuum in the power brake booster.
Keep the brake pedal depressed and start the engine.
If the brake pedal drops a little, the power brake booster is operating correctly.
If the brake pedal responds only slowly or not at all, the cause might be dirty air filters.
Check these, see operation Checking air filter in power brake booster.

Checking air filter in power brake booster




(in models with built-in power brake booster)
Remove the dashboard panel.
Slide the dirt guard, the cap and the air filters to the rear.
If necessary, pinch the air filters and remove them.
Clean the air filters and reinstall them.
Slide the cap and the dirt guard forward.
Install the dashboard panel.