The process of removing air from a hydraulic brake system is called bleeding. The air is compressed, and any air in the system is compressed during braking, causing the pedal to come loose. When braking, the correct order is recommended. This saves time and ensures that the whole system is bleeding.
The usual RWD program is to empty the components in the following order:
1. The master cylinder
2. Combination valve (if equipped with relief screw).
3. Wheel cylinder and caliper successively, starting with the longest brake line and ending with the shortest brake line. On most vehicles, the order is right back, left back, right front and left front. This may or may not be true for every car; The best advice is to use the bleeding sequence manually. Doing so might find the sequence.
4. FWD diagonal segmentation system; The order will be completely different and will vary by manufacture.
General Tips:
If the caliper has two release screws, release the inner part first and then the outer part. If drum brakes have two cylinders, drain the lower one and then empty the upper one. Most vehicles with ABS require special bloodletting procedures. Some are manual, some are caused by bleeding, and some require a scanning tool to start a pump or solenoid valve. View recommendations from specific manufacturers.
These are the most common (4) methods:
1. Gravity bleeding
2. Manual bleeding
3. Pressure bleeding
4. Vacuum bleeding
Gravity bleeding: The gravity method simply allows fluid to flow down the caliper and wheel cylinder.
Manual bleeding is the most common method. The master cylinder and brake pedal are used as pumps to allow fluid to flow through an open bleed screw. The fluid flow should flush the air.
Manual bleeding should be carried out smoothly to avoid turbulence in the liquid resulting in foaming. Foam fluid contains tiny bubbles that are difficult to remove.
Pressure relief Hydraulic oil flow through the bleed screw is usually done using a pressurized tank of brake fluid.
Pressure bleeding has the advantage of solo surgery and is an effective method of removing air and flushing hydraulic circuits.
Vacuum bleeding uses a pump to extract fluid and air from the drain screw. This is a simple and efficient operation.
Brake fluid: To ensure the maximum boiling point of the brake fluid and reduce corrosion, the brake fluid of the system using DOT 3 or DOT 4 brake fluid should be replaced every two years. This is a fairly simple operation, but it is not performed very often.
I strongly recommend it for two main reasons: security and the economy. Many FWD vehicles with heavy traffic will have brake fluid near the boiling point; As the oil boils, this will cause the pedal to pedal low. A quick tightening of the master cylinder and the ABS hydraulic regulator are very expensive parts that need to be replaced and the old oil will destroy them.