Workshops use a device to remove air, which is connected to the brake fluid expansion tank. The device creates pressure in the brake hydraulic circuit (max 2.0 bar).
If air has to be bled from the entire system, the operation is performed separately for each wheel brake cylinder. This is the case when air has penetrated into each brake cylinder. In the case where only one caliper or wheel brake cylinder has been replaced or repaired, it is usually sufficient to bleed the air from this cylinder.
The sequence of operations for removing air:
1 - rear right brake caliper, 2 - rear left brake caliper, 3 - front right brake caliper, 4 - front right brake caliper.
Remove the dust cap from the brake cylinder bleed valve. Clean the bleed valve, attach a clean hose to it, and insert the other end into a container half filled with brake fluid.
Ask an assistant to press the brake pedal until pressure appears in the brake system. This is felt by increasing resistance when pressing the pedal.
If sufficient pressure has been achieved, press the pedal all the way down and hold it with your foot.
Open the air bleed valve on the brake caliper with a key about one turn. Collect the leaking brake fluid in a container. Make sure that the end of the hose in the container is always below the level of the liquid poured into it.
Once the brake fluid pressure drops, close the air bleed valve.
Release the brake pedal and repeat the pumping process until the brake fluid pressure increases. Leave the brake pedal pressed, open the air bleed valve until the pressure drops, then close the valve.
The process of removing air from the brake cylinder is repeated until air bubbles stop flowing in along with the brake fluid that flows into the container.
After removing the air, remove the hose from the valve and place the dust cap on the valve.
Caution: When bleeding air, observe the fluid level in the expansion tank. The fluid level must not drop too low, otherwise air will be sucked in through the expansion tank. Always top up with new brake fluid!
Similarly, bleed air from the other brake cylinders.
After removing the air, top up the fluid level in the expansion tank to the MAX level. Check the rubber sealing gasket "1" for damage. Screw on the tank cap.
Attention: Perform a safety compliance check:
- Are the brake hoses tightened securely?
- Is the brake hose in the holder?
- Are the air bleed valves tightened?
- Is there enough fluid in the brake system?
- With the engine running, perform a leak test. To do this, apply a force of 200 to 300 N to the brake pedal for about 10 seconds (from 20 to 30 kg). Do not release the brake pedal. Check all connections for leaks.
After bleeding the air, the brake pedal should not "fall through". If this happens, repeat the procedure for bleeding the air from the brake system.
Note: Handle brake fluid as special waste.