Different bleeding procedures
The braking process is consisted of brake lines that lead from the master cylinder to each wheel and transport brake fluid. The result from the pressing of the brake pedal is that fluid presses the brake shoes against the drums or disc causing the wheel to stop. When you change a component or when you feel that the pedal becomes spongy, you need to bleed the system.
Manual brake bleeding
To do this you will need an assistant. First fill the master cylinder with fresh fluid. Then go to the wheel farthest from the master cylinder and locate the bleeder valve. Open it and ask your assistant to press and hold the pedal like that. In this time, fluid will go out of the system. Close the valve and ask the assistant to release the pedal. You have to repeat this several times until the fluid that comes out is clear and with no air bubbles. The same procedure applies to all the wheels. In the end you must refill the master cylinder.
This time you replace the assistant with a power bleed device. You use this on the master cylinder reservoir to seal it air-tight. Now the device pushes pressurized brake fluid through the master cylinder to the brake lines and eliminates the air. All you need to do is to open the valve and then close it when the air is removed.
Master cylinder bench bleed
Air can be trapped in the master cylinder as well, requiring bleeding. You can keep the cylinder in the vehicle or remove it and hold it in a vise. Locate the master cylinder piston and push a screwdriver repeatedly on it and hold it firm. You use a brake line wrench and temporarily crack the brake line fitting allowing brake fluid to come out. You must repeat the procedure to each brake line fitting.