How a Wheel Cylinder Works in Your Vehicle

a gray/silver car

The wheel cylinder is an important part of your braking system if you have drum brakes. If you have other kinds of braking systems, then you will also have a similar cylinder in your car, but it will not be exactly the same as the wheel cylinder used by the drum brake. This is a vital part of the stopping mechanism of these kinds of brakes. Knowing how this device works in your vehicle is an important piece of information that can help save you money at the garage.

What Is the Wheel Cylinder?

The wheel cylinder is a small round barrel, rather like a tiny rum barrel, that has a piston attached to either end so that it looks a little like a pregnant classical column. Each of the pistons are connected to the brake shoe, and the cylinder itself is connected indirectly to the brake pedal. When that pedal is depressed, fluid from the brake pipe moves into the wheel cylinder, the cylinder is filled with fluid, and the pistons are forced further outwards, coming into contact with the brake shoe and forcing it to touch the drum. This causes the car to brake. The harder the pedal is depressed, the harder the piston will touch the brake shoe.

Can the Cylinder Be Mended?

The cylinder is obviously a very complicated piece of machinery, but one which is essential to the good braking of your car. You may be lucky enough to have a warning light on your car telling you of cylinder failure, or you may first notice that your wheel cylinder is damaged when you find that you have to press more firmly on the brake to get it to stop. If this problem continues after the brake shoe has been removed and replaced, you will need to look at the wheel cylinder and see if that has been broken.

The cylinder can be broken, either by coming loose from its connections to the brake pedal or by loosing one of the pistons. If the piston has become dirty after regular use, it may fail to contract back into the cylinder. This will leave you with a brake shoe which is in constant contact with the brake drum in some circumstances, or not in contact at all in others. You will not be able to clean the cylinder yourself, and instead will have to either rebuild or replace it entirely.

In addition to being broken, the cylinder can also be corroded, due to the constant presence of fluid within the system. The corrosion cannot be fixed once it is there, but you can make sure that you don't get this problem by bleeding your brakes every so often.