2. Keeping the pedal depressed, start the engine. If immediately after starting the pedal slightly "fails", therefore, the vacuum brake booster is working properly.
Leak test
1. Run the engine for a couple of minutes, then shut it off. Slowly depress the foot brake pedal several times. If at first the pedal stroke gradually decreases with each squeeze, however, after three or four strokes it stabilizes, then the tightness of the vacuum booster assembly is not broken.
2. Depress the foot brake pedal while the engine is running. Keeping the pedal depressed, turn off the engine. If after 30 seconds of keeping the pedal depressed, its reserve stroke does not change, therefore, the tightness of the vacuum booster assembly is not broken.
Checking the amount of protrusion of the pusher rod
Remove the GTZ assembly from the vacuum booster (see Section Removal and installation of the main brake cylinder).
Note. There is no need to disconnect hydraulic lines from the GTZ - make sure that they are not deformed during the removal of the assembly. Using a manual vacuum pump, create a vacuum in the brake booster servo assembly to a depth of about 508 mm. rt. Art., press the pusher rod with a force of about 2 kgf and measure the length of the protrusion of the rod. Compare the measurement result with the requirements of the Specifications, if necessary, replace the amplifier assembly.
Replacement
Note. The vacuum brake booster unit cannot be repaired and must be replaced as an assembly in case of failure.
1. Remove GTZ (see Section Removal and installation of the main brake cylinder).
2. Disconnect the vacuum hose connected to the booster from the engine. Be careful not to damage the hose when removing it from the fitting on the booster assembly.
3. In the passenger compartment, remove the lower section of the panel trim and find the connection point for the vacuum booster pusher rod to the foot brake pedal (use a flashlight if necessary).
4. Remove the cotter pin, remove the cylindrical pin and disconnect the split finger of the pusher from the pedal lever.
5. From the cabin side, give four nuts securing the vacuum booster assembly to the bulkhead of the engine compartment, remove the washers (use a flashlight if necessary).
6. Go to the engine compartment and remove the vacuum booster assembly from the rear bulkhead. Pull the assembly strictly along the axis of its installation until the pusher rod is completely released from the bulkhead. Remove the assembly from the engine compartment.
7. Install in reverse order (first check the correctness of the setting of the adjusting dimensions).
Adjustment
Measure the distance from the end surface of the vacuum booster assembly to the hole in the split pin of the pusher rod. Compare the measurement result with the requirements of the Specifications, if necessary, loosen the locknut and turn the split pin to achieve the required value. Don't forget to tighten the locknut.