Attention! When handling brake fluid, keep the following in mind:
- Brake fluid is poisonous. Under no circumstances should it be sucked out by mouth through a hose. Pour brake fluid only into containers that prevent human misuse
- Brake fluid is corrosive and should not come into contact with car paint. If brake fluid gets in, wipe it off immediately and wash the surface with plenty of water
- Brake fluid is hygroscopic. this means that it absorbs moisture from the air, which lowers its boiling point. Therefore, store brake fluid only in closed containers
- Brake fluid that has already been used once in the brake system must not be refilled. When removing air from the brake system, fill only with new (fresh) brake fluid
- Brake fluid specification: FMVSS 116 DOT 4
- Brake fluid must not come into contact with petroleum products. Even small impurities of petroleum products make the brake fluid unusable or lead to failure of the brake system. Plugs and cuffs of the brake system become unusable when in contact with products containing petroleum products. When cleaning, do not use rags soaked in petroleum products
- Brake fluid should be changed every two years, if possible after the winter period of operation
Attention! Brake fluid must be disposed of at designated collection points.
Air removal
After any repair of the brakes, in which the brake system was opened, air can enter the pressure lines of the hydraulic drive.
In this case, it is necessary to remove this air from the brake system.
The presence of air in the pipelines can also be judged by the fact that when you press the brake pedal, no strong resistance is felt. In this case, it is necessary to eliminate the leakage and remove air from the system.
In workshops, bleeding from the system is carried out using a combined device for filling brake fluid and bleeding the brake system.
Attention! It is mandatory to use a combined device if the brake hose was disconnected, one of the chambers of the expansion tank was completely emptied, or if it is necessary to bleed the clutch hydraulic drive.
In all other cases, you can do without the specified device. In this case, the air from the brake system is removed by pumping with the brake pedal. An assistant is needed for this operation.
If you need to bleed the entire system, then you need to remove air from each wheel cylinder. This is necessary when air enters all wheel cylinders. In this case, a combined device should be used.
If the caliper of only one brake mechanism was replaced or repaired, then, as a rule, it is enough just to remove air from the corresponding wheel cylinder.
Attention! If one of the chambers of the expansion tank for the brake fluid has been completely emptied, for example, due to a leak or due to inattention when bleeding the brake system, then the fluid should be drunk. It is also recommended in such cases to contact a workshop to remove air from the brake system. because air in this case enters the ABS hydraulics. If the vehicle is equipped with an EDS system, you must first bleed the brake system, and also perform a basic adjustment using a diagnostic tester.
When installing a new brake hose, the system must also be bled using a combination tool.
Air removal sequence:
- A) brake mechanism of the front left wheel;
- b) brake mechanism of the front right wheel;
- V) rear left wheel brake;
- G) rear right wheel brake.
1. Mark the direction of rotation of the wheel with an arrow on the sidewall of the tire and loosen the wheel bolts.
2. Jack up the car, jack it up and remove the wheels.
Attention! Access to the fittings for pumping the brake mechanisms of the rear wheels is possible only after removing the rear wheels.
3. Add brake fluid to the expansion tank up to the maximum mark.
Attention! Loosen the bleeder fittings carefully so as not to strip the threads. It is recommended to apply a rust converter to the fitting threads two hours before bleeding the system or caliper. If the fitting, despite the measures taken, does not open, it is recommended to contact the workshop and perform pumping there.
Attention! During pumping from time to time check the level of brake fluid in the expansion tank. The level of brake fluid in the reservoir must not be allowed to drop to the limit or that the reservoir was at all «devastated» In this case, air will be pumped into the system. Replenish the amount of brake fluid in the expansion tank, adding only fresh fluid.
4. Remove a protective cap from the union of prorolling of the working brake cylinder.
5. Clean the fitting, put a clean hose on it, lower the other end of the hose into a container half filled with brake fluid (see illustration).
6. Ask an assistant to depress the brake pedal to the end («sway») several times until the pressure builds up in the brake system. It is felt by the increase in resistance when the pedal is depressed.
After the appearance of sufficient pressure, the pedal should be squeezed out to the stop and held in this position.
7. Unscrew 1 bleed screw about half a turn with a wrench (see illustration).
Collect escaping brake fluid in a container. To unscrew the fittings, use a wrench designed for unscrewing the bleeding fittings, for example, HAZET 4968/5. Make sure that the end of the hose in the container for collecting the escaping brake fluid is constantly below the fluid level.
8. Wrap the prorolling union as soon as pressure of a brake liquid in system decreases.
9. Repeat pressurizing the brake system with the brake pedal. Then press the brake pedal down to the stop and hold it with your foot. Open the bleeder valve and, as soon as the pressure in the system drops as the brake fluid flows out, close the bleeder screw.
10. Repeat bleeding the system on one wheel cylinder until no more air bubbles appear in the liquid flowing into the container.
11. After removing the air, remove the hose from the bleeder fitting, tighten the fitting with a force of 10 Nm and put a dust cap on it.
In the same way, remove the air from the remaining wheel cylinders, while observing the bleeding sequence.
After bleeding is complete, add brake fluid to the expansion tank up to the MAX mark.
Ventilation with combined device
12. Remove the cover from the expansion tank with brake fluid and screw on the bleeder adapter instead.
13. Create an operating pressure of 2 bar in the brake system.
14. Vehicles with EDS. First, bleed the air from the brake system if one of the chambers of the expansion tank was emptied during its calcination. First, bleed the brakes of the front wheels at the same time, and then the rear wheels. To do this, put a hose on the fittings of both mechanisms, open the fittings and let the brake fluid drain until no air bubbles appear in it. After that, close the fittings and configure the system using a diagnostic tester. After adjustment, bleed the brake system again.
15. All cars. Bleed the air from each brake cylinder following the bleeding sequence above. To do this, put a hose on the fitting, open the fitting and let the brake fluid drain until no air bubbles appear in it. After that close the fitting.
16. Remove the adapter from the expansion tank together with the bleeder. At the same time, remember that. that the brake system is under pressure.
17. Bleed each brake additionally in the usual way without a bleeding device at least 5 times.
18. Establish the removed wheel according to the marks put at removal.
19. Screw in wheel bolts and lower the car on wheels.
20. Tighten the wheel bolts in a cross pattern to 120 Nm.
Attention! Make sure that:
- A) brake hoses are securely connected,
- b) brake hoses are fixed in holders,
- V) brake bleeders are screwed on,
- G) there is enough brake fluid in the expansion tank.
21. Perform a brake leak test by starting the engine. To do this, depress the brake pedal with a force of 200-300 N (20-30 kg) and hold it for about 10 seconds. The pressure in the system and, accordingly, the resistance of the brake pedal, should not decrease. Check all connections for tightness.
22. Apply a few brakes on a light road. At least one braking should be done with the ABS active, which is felt by the pulsation of the brake pedal.
Attention! When checking the brake system in this way, take into account the situation on the road and keep an eye on the traffic behind you.
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