When increasing the force on the brake pedal, it is necessary to check the performance of the vacuum booster
Checking the brake booster
Depress the brake pedal to the stop several times with the engine off and, keeping the pedal depressed, start the engine.
At the same time, due to the pressure drop in the cavities of the booster, the brake pedal should move forward.
If this does not happen, check the tightness of the vacuum booster hose connections and, if necessary, eliminate air leakage.
If this still fails, then the amplifier is defective and needs to be replaced.
To check the tightness of the vacuum booster, open the hood and start the engine for 1 minute.
Approximately 30 seconds after the engine has been turned off, press the brake pedal 2 times, while a characteristic hiss of air entering the amplifier should be heard.
Otherwise, replace the amplifier.
Blow out the hose with check valve at both ends.
Air must only pass through the side of the non-return valve. Otherwise, replace the non-return valve.
Replacing the vacuum brake booster
Remove the main brake cylinder without disconnecting the brake pipes from it (see Removing the main brake cylinder).
Loosen the clamp with a screwdriver
Remove the vacuum supply hose from the fitting.
The hose can also be removed with the fitting.
Remove the lock washer from the cabin side with a screwdriver.
Holding the pusher eye bolt with the “19” key, unscrew the nut with the “17” key
Remove the bolt from the pusher eye.
Remove two plastic bushings from the pusher eye
Using a “13” head with an extension from the cab, unscrew the four nuts securing the amplifier to the partition of the engine compartment
Remove the amplifier.
Remove the paronite gasket.
We install the new vacuum booster in the reverse order, while for the correct operation of the brakes, the position of the adjusting bolt should be adjusted.
To do this, holding the pusher with the “8” key, unscrew the lock nut with the “10” key.
Then, with the “8” key, unscrewing or tightening the bolt, ...
We achieve such a position in which the gap between the mating plane of the amplifier and the bolt head is within 1.35–1.65 mm.
After that, while holding the bolt, tighten the locknut.
Having lubricated the plastic bushings, we install the booster, after which we adjust the brake pedal travel.
To do this, holding the pusher of the amplifier with the “8” key (for clarity, it is shown on the removed amplifier), unscrew the lock nut with the “14” key and, ...
By rotating the pusher eye, we set the distance between the center of its hole and the mating surface of the vacuum booster housing - 131–133 mm.
Installing the master brake cylinder.
The free travel of the brake pedal with the engine off should be 3–5 mm.