Contaminated brake fluid
A hydraulic braking system is using brake fluid to produce friction against the discs or drums, resulting in stopping the vehicle. This fluid in time gets old and can have air trapped inside, or other contaminants. For this, there is the bleeding procedure that cleans the system.
First you need to make sure the master cylinder is full. It is usually located under the hood near the engine compartment on the driver’s side. Remove the cover from it and check the level. After that you will need to find the bleeder valve, in order to mount a tube on it, through which the fluid will pour inside a plastic container, already filled with fluid.
The main activity here is pressing and holding the brake pedal. By doing this, fluid will go through the tube and into the container. When the pedal is released, the bleeder valve must be closed so that air won’t go into the system. Always check the level on the master cylinder. It must always be half full, because otherwise air will get in the system as well.
Closing the system
You stop the bleeding when the fluid coming through the tube is clean and clear. Remove the tube from the bleeder and wipe the remaining drops. Again you must refill the master cylinder. Repeat the procedure to the remaining wheels as well.