Bleeding your brakes is one of those things that young mechanics learn early. Most start by sitting in the seat, pressing the brake pedal when your father yells; “Push it down and hold it.” We all do what we are told. “Now, let it up.” You do it or risk getting the wrath of your angry old man. An old man with no sense of humor concerning the boring redundancy of brake pedal actuation in the bleeding process. As you repeat the process for all four wheels, you wonder if there was a way to simplify the procedure.
Our friends at Classic Performance Products (CPP) have found the silver lining in replacing a major component of the brake system. If you are replacing the brake system’s master cylinder, there is good news. Bench bleeding the master cylinder can be done before the process of bleeding the entire brake system, which significantly reduces the bleeding process in the car. Bench bleeding is typically done on a workbench (hence the name), and probably with the master cylinder held securely in a bench vice.
Why Do You Have To Bleed Brakes Anyway?
The brake system in a car is a closed hydraulic system that relies on the fluid to move energy created by stepping on the brake pedal, to actuate a hydraulic slave cylinder which applies braking pressure to the brake rotors or drums.
Anytime the system is opened, through mechanical means or component failure, air can enter the system. However it happens, air that gets into the brake system must be removed because it acts as a sponge to absorb the transfer of energy. Air is easily compressed where hydraulic fluids are not. Therefore, if the energy is being used to compress air in the system, it is not being used fully by the slave cylinder. In order to restore complete braking potential, the air bubbles must be removed through the brake bleeding process.
Bench bleeding ensures that air bubbles in the integral passageways of the master cylinder are completely removed. Attempting to bench bleed the master cylinder in the car will not be effective because the power booster does not actuate the master cylinder’s piston the full length of travel, so air will still be trapped in the passages. Trying to get these air bubbles out will leave you with a mess that you could have avoided if you had bench bled the unit.
What You Will Need:
- Bleeding syringe (Part #CP0105)
- Bleeder kit (Part #CPP-BK)
- Brake Fluid
- Bench Top Vise
You can try to bleed the master cylinder without CPP’s bleeder kit, but you will risk contamination of the fluid or difficulty with the proportioning valve. The kit contains a tool that keeps the proportioning valve in place while bleeding, making the process an easier task.
For more information on this or other information on braking systems, please visit CPP online at www.classicperform.com.