Brake Wheel Cylinder Replacement
What is a brake wheel cylinder?
Wheel cylinders are the component used to press the brake shoes against the inner lining of the brake drum on a drum brake system. They are the drum brake equivalent to the brake caliper used on disc brakes.
How does the brake wheel cylinder work?
The wheel cylinder functions by use of hydraulic pressure supplied by the master cylinder. When the wheel cylinder receives this pressure, both ends are pressed outward, forcing the brake shoes into the brake drum. The brake drum rotates with the wheel, so the hydraulic pressure from the wheel cylinder is transferred to the shoes, then the brake drum, and ultimately slows or stops the tires.
Wheel cylinders need to be replaced when they begin to leak fluid, as they can damage other components and become corroded. Replacing them is recommended as preventative maintenance when other brake work is being performed.
If fluid from a leaking wheel cylinder has contaminated the brake shoes, the shoes will need to be replaced.
What are the symptoms related to a bad brake wheel cylinder?
Brake wheel cylinder failure occurs in two different ways, with two opposite symptoms. The wheel cylinder can become seized, in which case it will not release the brake shoes from the rotor. The seized cylinder will cause the vehicle to brake constantly on one side of the vehicle, forcing the vehicle to move toward that side. Also, this pulling will be accompanied by a strong odor from one wheel. Another way wheel cylinders fail is by leaking. If there is a leak, the brake pedal will be noticeably easier to push, and will sink all the way to the floor when held. After only a few repetitions of pressing the brake pedal, the braking ability of the vehicle may become completely compromised. There may also be brake fluid leaking onto the wheel.
Can I drive with a brake wheel cylinder problem?
It is not safe to operate any vehicle with any braking problem. If there is any sign that the brakes are not performing as originally intended, the vehicle should immediately be placed out of service, and repaired.
How often do brake wheel cylinders need to be replaced?
Wheel cylinder failure on some vehicle's is more frequent than others. On most vehicle's, they will need replacement at some point. It is most common to replace wheel cylinders on vehicle's with over 75,000 miles.
How are brake wheel cylinder issues diagnosed?
Upon a visual inspection, the servicing technician will notice the brake shoes are severely worn on one wheel, the wheel cylinder does not provide sufficient clamping force to stop the vehicle, or brake fluid leaking out of the brake drum. The wheel cylinder in question will be inspected to verify a reliable diagnosis has been reached.
How is a brake wheel cylinder replaced?
Replacement requires removal of the wheel and tire, brake drum, brake shoe hardware, and brake shoes. Then the brake line is disconnected from the wheel cylinder, and the cylinder is unbolted and removed. Once the new wheel cylinder is installed the brake shoes, brake shoe hardware, brake drum, and wheel are installed. The brakes will then be flushed, bled of air, and adjusted prior to placing the vehicle on the ground and tightening the wheel nuts to proper specifications.
We recommend having the brake hydraulic system flushed any time a component in the hydraulic system is replaced or if the hydraulic system is opened.