The reasons for a malfunction of the main brake cylinder are wear or loss of elasticity of the cuffs, wear of the working surfaces of the cylinder and pistons, swelling of the cuffs (due to the ingress of mineral oils into the system), clogging of the compensation hole.
If the fluid level in the reservoir of the master brake cylinder has decreased, and when examining the connections of pipelines and assemblies, including the brakes, no fluid leak is found, then in this case the brake fluid may leak through the outer cuff into the vacuum booster cavity.
If, when a constant force of 50-100 N (5-10 kgf) is applied, the brake pedal moves halfway, and then gradually moves to the cab floor, the main cuffs are damaged or swollen.
In the event of swelling of the cuffs and the valve of the secondary piston, non-braking of the system may occur.
To determine this malfunction, it is necessary to disconnect the pipes from the master cylinder.
In a serviceable cylinder, liquid dropping (gravity) from both cylinder bores and a decrease in the liquid level in the tank should be observed.
To remove the master cylinder, you need a 13 wrench, a TORX E30 wrench, a syringe or a bulb, a flat-blade screwdriver, a 12 special wrench for the brake pipe nuts.
Disconnect the negative cable from the battery.
We pump out the brake fluid from the reservoir of the master brake cylinder with a rubber bulb or syringe.
Disconnect the brake fluid level sensor wiring block
We loosen the tightening of the hose clamp in the clutch drive
We move the clamp along the hose and disconnect the hose.
After disconnecting the hose, do not lower it down, but secure it in the upper position in any way possible.
The brake fluid will remain in the hose, then after installing the reservoir, it is not necessary to pump the clutch release hydraulic drive.
Unscrew the screw securing the reservoir to the master brake cylinder
Removing the tank
If during operation there was a leakage of brake fluid through the connecting sleeves, pry the sleeves with a screwdriver and remove them from the holes in the cylinder body.
Before installing the reservoir, insert new connecting sleeves into the holes of the brake master cylinder.
To facilitate the installation of the connecting sleeves into the cylinder and the reservoir pipes into the sleeves, moisten them with fresh brake fluid.
Unscrew the pipe fastening nuts
Moving the pipelines to the side
We put suitable plugs on the tubes or wrap them with a piece of cellophane film.
We unscrew the two nuts securing the brake master cylinder to the vacuum booster
Remove the master brake cylinder
Before installing the reservoir, insert new connecting sleeves into the holes of the new brake master cylinder.
Install a new O-ring on the brake master cylinder.
Install the master brake cylinder in reverse order.
Fill in the brake fluid and bleed the brake system (article - Fluid change and brake bleeding Gazelle Next).
Removal and installation of the vacuum amplifier
The performance of the vacuum amplifier is checked as follows.
When the engine is not running, it is necessary to press the brake pedal 3-4 times, and then, keeping it pressed with a force of 300-400 N (30-40 kgf), start the engine.
If the amplifier is working properly, the pedal will move to the floor and you will hear a hiss of air passing through the amplifier filter.
If the pedal does not move or is difficult to move, the cause is a defective amplifier.
It is also necessary to make sure that the vacuum amplifier and the check valve are tight.
To do this, stop the engine, wait 1-2 minutes and press the pedal several times.
During the first three clicks, you should hear the noise of the air entering the amplifier.
If this does not happen, the vacuum booster or check valve is faulty.
To remove the vacuum amplifier, you need a socket for 13, a Phillips screwdriver.
Loosen the clamp and disconnect the hose from the vacuum check valve
Remove the master cylinder as described above
The master cylinder can be retracted without disconnecting the tubes.
Remove the lower decorative instrument panel
Disconnect the vacuum booster pusher from the brake pedal. Slide the finger spring retainer to the side
Remove the retainer
We remove the finger from the holes of the pusher fork and pedal
We unscrew the four nuts securing the vacuum brake booster to the bulkhead and remove the vacuum booster towards the engine compartment.
Install the vacuum amplifier in reverse order.
If the pipes of the master cylinder were unscrewed, then fill in the brake fluid and pump over the brake system.