All About The Brake Cylinder

The brake cylinder, a small 2″ by 3.5″ piece of empty metal, it has such an important job to do! Let me tell you all about the brake cylinder.

The brake cylinder is used in the drum brake which is on the rear wheels. Not all vehicles use drum brakes in the rear. Some use the disc brake system for all four wheels. The 1989 Chevrolet Dually employs disc brakes on the front and drum on the rear.

From the moment you decide to step on the brake to the moment that the brakes actually contact the rotor, or drum, is just seconds. Every part of the brake system is important.

The .gif below will give you a good idea of how the brake cylinder is actuated and what it does when it is:

Did you notice in the above .gif, on the backside of the cylinder, there is a brake fluid line connector and a bleeder valve. The bleeder valve is where you place a hose line to bleed the air out. Anytime you have removed a brake part that opens the brake lines to air, you must bleed the system of that air.

When I replaced the brakes and cylinders on my truck I only bled the rear brakes. Since I did not expose the front brake lines to air it was not necessary to bleed them.

When, or if, you need to bleed the whole system, you always start at the brake farthest away from the Master Brake Cylinder under the hood. On most vehicle that would be the right rear brake. Then, work your way to the left rear, right front then left front.

And that’s about all there is to the brake cylinder!

By the way: The boot on the pegs, on either side of the cylinder, can become worn by a piece of the brake that is right up against the rubber boot. This is a spot to pay particular attention for when looking for a leak in the brakes. It’s difficult to see the back side of the boot that is up against the metal, but is many times exactly where the leak is at.

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