Air is removed from the brake system by bleeding the brake pedal, which requires an assistant.
Note: The work performed on a vehicle equipped with ABS and without it is similar. At service stations, air is removed using a special installation connected to the expansion tank. When using this installation for a vehicle equipped with ABS, the brake system is released from air and by pressing the brake pedal.
If it is necessary to bleed the entire system, the air is removed separately from each cylinder. This is necessary if air gets into all cylinders. If only one wheel cylinder was replaced or repaired, it is usually sufficient to bleed the corresponding brake cylinder.
Air removal sequence:
- 1. Rear right brake caliper.
- 2. Rear left brake caliper.
- 3. Front right brake caliper.
- 4. Front left brake caliper.
Remove the boot from the brake cylinder air bleed valve. Clean the valve, put a clean hose on it, lower the other end of the hose into a container half filled with brake fluid.
The container should be positioned at least 30 cm above the bleed valve. This prevents air from entering the brake system through the bleed valve thread.
The assistant "pumps" the brake pedal until pressure is created in the system. This is felt by the increased resistance when pressing the pedal.
Once sufficient pressure has been created, press the pedal all the way down and keep your foot on the pedal.
Open the valve about half a turn. Collect the flowing liquid in a vessel. Make sure that the end of the hose is always in the vessel below the liquid level.
Release the brake pedal and press it about 12 times (pump up). The pedal does not offer resistance. Brake fluid flows through the hose into the container. Keep the brake pedal pressed, and have the assistant close the air bleed valve.
Repeat the process of removing air from one cylinder until there are no more air bubbles in the liquid flowing into the vessel.
After removing the air, remove the hose and put the boot on the valve.
Remove air from other cylinders in the same way.
Caution: During the bleeding process, monitor the fluid level in the expansion tank from time to time. The fluid level should not drop too low, otherwise air will be sucked in through the tank. Top up with new brake fluid only!
After removing the air, add brake fluid to the expansion tank up to the MAX mark.