The wheel cylinder is a critical component of your drum braking system. Usually mounted behind the drum or backing and typically above the shoes, these two way valves can often leak and fail, causing a dangerous braking condition. When you press on your brake pedal, the brake master cylinder piston pushes the hydraulic brake fluid through the brake lines and eventually into your wheel cylinders.
Wheel cylinders are hydraulic valves with two pistons mounted opposite of one another. When the brake fluid pressure forces the pistons apart, the action moves the brake shoes against the drum, bringing the vehicle to a stop.
This very small mechanism works much like your slave or master cylinder, and as such can leak from it's seals or become contaminated. When you have a problem with your brakes not responding as well as they once did, or your rear drum brakes leaking, replacing your wheel cylinders can be a quick and inexpensive fix.
Similar to the internal seals of a brake master cylinder, there are protective cups that seal the wheel cylinder from the outside elements. Over time and through many heat cycles, these rubber cups can deteriorate and fail. When this happens, your brake pedal will become spongy and non-responsive, and you may leak brake fluid.
Not only are these internal seals prone to failure, the exterior dust boots that cover each end of the piston and cylinder in which the piston travels can fail as well. Make sure to check our chart for your year make and model.
Needless to say this is a dangerous condition, and one that should be remedied right away if you want to drive your vehicle. Luckily, we have the guide to help you do this on your own, and if you don't find your application fill out our request a DIY form at My Pro Street for some help.