How to Know if You Have a Bad Wheel Cylinder

The wheel cylinder is a key component of a drum brake system. There is one on each drum brake. The wheel cylinder takes the hydraulic pressure that is sent from the brake pedal when you apply the brakes, and then uses it to push the brake shoes (which contain the friction material) against the metal brake drums, thereby slowing and stopping the car.

Does your car have drum brakes?

Drum brakes are usually found only on the rear wheels of modern vehicles, but not on all of them. Since the disc brake first became widely available on production cars in the 1970s, it has been universally adopted for the front brakes, which do the vast majority of the braking work in a four-wheeled vehicle.

To check on whether your car has drum brakes and wheel cylinders, look in your owner’s manual, in the “Specifications” section.

What are the signs of a failing wheel cylinder?

Once you have determined whether your car has rear drum brakes, there are several ways to tell that a wheel cylinder might be failing. Let’s go through the list:

• Your brake pedal feels soft or goes down farther than usual before working: This is a strong indication that you are losing brake fluid, possibly through a failing wheel cylinder. Check your brake fluid level in the reservoir under the hood, and top it up if necessary with the brake fluid that is recommended by your owner’s manual. Call your mechanic and have your braking system checked out right away.
• Your car’s brakes don’t stop the car well or evenly: You may notice that it takes a longer distance to stop your car, that there is a delay in response when you apply the brakes, or that it pulls to one side when you apply them. This can be a sign of a failing wheel cylinder. Call a mechanic immediately and have the problem fixed.
• Your brakes make an unpleasant noise: Sometimes, a failing wheel cylinder can stick in the “on” position, pushing the brake shoes into permanent contact with the brake drum. This can make a constant noise, which may turn into a grinding sound if you neglect it, as the friction material wears away to the bare metal. This may also create a bad smell, from the friction material being in constant contact with the drum, and steadily being “burned” away.
• You see a brake fluid leak on your rear wheels or tires: A failing wheel cylinder will often leak brake fluid onto a rear wheel or tire. You may notice a pool of fluid on the ground in this area, or you may need to look on the insides of your rear wheels with a flashlight to spot it. This is a sign that your car needs immediate brake system repairs.

Should you drive your car with a failing wheel cylinder?

The safest course of action when you discover a braking problem in your vehicle is to not drive it. Losing your brakes can cause accidents, sometimes with serious or fatal consequences. If you notice any sign that the brakes are not performing as originally intended, the vehicle should immediately be placed out of service. Do not compromise the safety of yourself or your passengers. Call a mechanic for guidance, which will probably include a tow to the repair shop.

How do you fix a failing wheel cylinder?

The easiest and most foolproof way to fix a failing wheel cylinder is simply to replace it. This involves disconnecting the brake line that carries the brake fluid to the wheel cylinder, removing the old wheel cylinder from its backing plate, attaching the new wheel cylinder to the backing plate, reattaching the brake line, bleeding any air from the brake line, and testing the new wheel cylinder to be sure it works correctly.

Can you replace a failing wheel cylinder by yourself?

Unless you have a fairly high level of knowledge and experience in automotive braking systems, you should not attempt to repair a failing wheel cylinder. You could cause more problems than you solve, due to the difficulty of working on brake components that are constantly exposed to the elements. Parts of the wheel cylinder assembly can corrode and rust together over time, which makes it very likely that you might break things as you attempt to disassemble them. Then you will have a much larger problem on your hands!

This is the perfect job for a professional mechanic, who has lots of experience dealing with failing wheel cylinders.