Attention! Bleed the brake system while wearing goggles. If brake fluid accidentally gets into your eyes, rinse immediately with plenty of water and seek medical attention!
Note. Bleeding the hydraulic system is carried out in order to remove air from it that enters the path when servicing the brake mechanisms, replacing hydraulic lines or GTZ, as well as when lowering below the minimum allowable value of the liquid level in the master cylinder reservoir.
1. If air has entered the system due to a drop in the liquid level in the GTZ tank, or when the brake lines are disconnected from the GTZ, the brake mechanisms of all four wheels must be pumped. When disconnecting the lines from any of the calipers/wheel cylinders, it will be enough to pump only this particular brake mechanism.
2. If the brake line was disconnected from the fitting located between the GTZ and one of the brake mechanisms, only this part of the brake circuit is pumped.
3. Depress the foot brake pedal several times with the engine off to release the residual vacuum in the vacuum brake booster. Remove the cap from the GTZ reservoir, add fresh fluid to the reservoir if necessary, then place polyethylene under the cap and screw it into place.
Note. Remember to check the fluid level in the reservoir regularly while pumping. An excessive drop in the level is fraught with air entering the GTZ, which will nullify all the efforts made and entail the need to pump the entire brake system.
4. Enlist the help of an assistant, prepare a supply of fresh brake fluid, a transparent container partially filled with brake fluid, a piece of plastic hose that fits tightly over the bleed valve, and a suitable open-end wrench to release / tighten the valve.
Models with ABS
1. When replacing the GTZ, or after excessive lowering of the hydraulic fluid level in its reservoir on ABS-equipped models, begin the procedure by bleeding the brake lines connected to the master cylinder. Ask the assistant to slowly squeeze the gas pedal to the stop and hold it in the lower position. Loosen the fitting connections of the brake lines supplied to the GTZ one by one, releasing the liquid mixed with air from them. Repeat the procedure until air bubble-free liquid begins to be ejected from the cylinder. Now you can proceed to pumping the hydraulic pressure modulator.
2. To bleed the modulator, firmly place a piece of plastic hose on its bleed valve. After starting the engine, pressurize the modulator, then release the valve by 1/8÷1/4 turn, releasing the brake fluid mixed with air.
Attention! The hydraulic fluid in the modulator is under high pressure. Never loosen the bleed valve more than 1/4 turn to avoid a sudden burst of hydraulic fluid. Shut off the engine and bleed the rest of the braking system (see below).
Note. When the ABS warning lamp on the vehicle's instrument panel comes on, the procedure described in the last paragraph must be repeated.
All models
1. Slightly loosen the right rear brake bleed valve, then tighten it again so that it releases quickly and easily during the procedure.
2. Pull a suitable plastic or rubber hose over the valve, lower the other end into a transparent vessel partially filled with clean brake fluid (see accompanying illustration). The end of the hose must be completely immersed in the liquid.
3. Ask an assistant to slowly depress the foot brake pedal several times, thereby raising the pressure in the system.
4. With the brake pedal fixed in the lower position, slightly open the bleed valve so that brake fluid begins to be forced out of it. Watch for fluid to exit from the submerged end of the hose. After a couple of seconds, when the pressure weakens, close the valve and allow the assistant to release the pedal.
5. Repeat the procedures of the last two paragraphs until fluid free of air bubbles begins to flow from the valve, then go to the brake mechanism of the left front wheel. In the same manner, bleed this mechanism, then the mechanisms of the left rear and right front wheels.
Attention! Always make sure that the liquid level in the GTZ reservoir does not drop too low!
6. Never add old brake fluid to the reservoir - it is highly hygroscopic and absorbs a lot of moisture over time, which leads to a drop in its boiling point and, as a result, to a decrease in braking efficiency. In addition, the presence of moisture in the hydraulic system contributes to the accelerated aging of the material of flexible brake hoses.
7. Upon completion of pumping, add fresh brake fluid to the GTZ reservoir, bringing its level back to normal.
8. Check up efficiency of functioning of brakes. When depressing the pedal, it should provide firm resistance - a feeling of softness of its stroke indicates the presence of air in the hydraulic circuits and the need to repeat the pumping procedure.
Attention! In no case do not start operating the car without being absolutely sure that the brake system is working properly!