How Brake Bleeding Works

If you want to bleed your brakes alone, there are a couple of products designed to make your job a lot easier. These items can be purchased at the auto supply store or obtained online.

Vacuum pumps work by sucking the brake fluid out of the system through the bleeders. There can be a problem, however, if the pump is not securely attached to the bleeder threads. Air can sneak into the line if the bleeders aren't clean. Before attaching the pump, clean the bleeder and the bleeder hole with brake cleaner. Not all vacuum pumps are the same. Read your owner's manual to learn how to use the pump properly.

Pressure pumps work by forcing the brake fluid out through the bleeder valves. The fluid-filled pump attaches to the master cylinder and forces pressure through the system as you open one valve at a time. Because the pump holds fluid, you don't have to refill the fluid reservoir constantly. [source: Dempsey]

One-way check valve bleeder screws allow the air and fluid to come out while snapping closed before air can get back in. Attach the check valve to the bleeder on one end, and attach your clear tubing to the other end. Apply pressure to the brake pedal, and the check valve works like a hiccup — no air will go back in.

With the vacuum and pressure pump methods, you will need to bleed each line several times to make sure no air was moved through the system.

Have a friend you want to torture? Read on to learn about the wildly popular two-person pump-and-hold method.