How to Replace a Brake Wheel Cylinder
A wheel cylinder is an important braking component. Its purpose is to hydraulically expand brake shoes causing them to tighten against a brake drum. Thus, they assist in stopping the vehicle. On newer vehicles, wheel cylinders are usually only found on the rear brakes. Some vehicles with 4 wheel disc brakes no longer use them but rather have replaced the wheel cylinder with abrake caliper. However, wheel cylinders are still commonly used on your vehicle, and remain on many used vehicles. Remember, these are general directions. If you require more detailed instructions, contact us or you may want to purchase arepair manual specifically designed for your vehicle. A wheel cylinder is usually a very dependable component. However, with wear, they can begin to leak brake fluid past the inner pistons.
When this happens, it can cause the rear brakes to leak brake fluid, grab or lock up, you may notice a slightly lower brake pedal, and in the some cases cause the rear braking system to fail completely. Please understand that in the event that the rear brakes fail, the manufacturer’s have designed into thebrake master cylinder a safety that will allow the vehicle to still have front brake assistance. Therefore, even though the brake pedal may go to the floor, you should be able to stop the vehicle. Note: If the wheel cylinder is leaking and the brake shoes are saturated with brake fluid, they need to be replaced. If there is only a small amount on them, spray them with brake cleaner, wipe them dry, and we recommend sanding them clean with sandpaper. We also recommend that before going further, spray the steel brake hose fitting that screws into the rear of the wheel cylinder (behind the backing plate) with a quality penetrating oil so it is easier to remove.
Park your car on level ground with the engine off and theemergency brake off. Block both sides of the front wheels. Always raise a car according to the manufacturers recommended instructions and secure with jack stands. Also, we will be dealing with brake fluid so be sure to wear protective clothing, eyewear and gloves.
Tools and Supplies Needed to Complete this Job
- Hydraulic Jack
- Jack Stands
- Wrench set
- Line wrench set
- Ratchet and socket set
- Pan to collect brake fluid
- Brake cleaner
- Penetrating oil
- Vacuum hose or plug to fit over steel brake hose to eliminate fluid leakage
- Brake fluid
- Replacement wheel cylinder
- Brake shoe removal tools
Step 1 - Locate and release the hood latch, then release the secondary hood safety release and raise the hood.
Step 2 - Remove the hub cap if applicable.
Step 3 - With the vehicle still on the ground, loosen the wheel’s lug nuts ¾ of a turn.
Step 4 - Double check the blocks on the frontwheels so the vehicle can’t move, then jack the wheel to be worked on off the ground.
Step 5 - Place a jack stand under the vehicle’s frame or the manufacturer’s recommend location to support the vehicle’s weight. (note: never work under a vehicle that is not safely supported with a quality jack stand. Never trust a hydraulic jack alone to hold the vehicle’s weight. Hydraulic seals can fail causing the vehicle to fall.
Step 6 - Now that the vehicle is safely lifted and secured on the jack stand, remove the lug nuts and the wheel. This is a good time to spray the steel brake line fitting with penetrating oil where it attaches to the wheel cylinder so it can begin loosing the any rust that exists.
Step 7 - Now that the wheel is off, the brake drum needs to be removed. Often they are difficult to remove and require the brake shoes to be lowered. If that is the case, behind the backing plate is a rubber plug. Remove the plug and loosen the star wheel (self adjuster) to loosen the shoes. If you turn the wrong way, the drum will get tighter and not turn. If the self adjuster will not allow you to loosen the brake shoes you will need to push a small flat blade screw driver to release the adjuster arm.
Step 8 - Once the drum is removed, place a drip pan under the brake shoes and inspect the brake shoes and hardware for any damage. If the shoes are saturated with brake fluid, replace them. Using brake cleaner, spray the area to eliminate dirt and brake fluid. Remove thebrake hardware and brake shoes.
Step 9 - Next, with your drip pan in place, locate the steel brake line on the backing plate where it screws into the wheel cylinder. If you have line wrenches, use the correct one to loosen the steel brake line. A standard open end wrench will work; however, they are more likely to strip or damage the brake line fitting. (note: when removing the steel brake line fitting, you can easily damage the steel tubing). Work the line a little at a time while you continue spraying penetrating oil on the fitting to help eliminate damage.
Step 10 - Then, prepare a small piece of vacuum hose that will fit tightly over the steel brake line. Place a bolt or screw in one end. Fully remove the fitting and place the vacuum hose over the line to eliminate brake fluid from leaking out of the system.
Step 11 - Locate the two retaining bolts on the backing plate that hold the wheel cylinder in place. With a socket/ratchet or wrench, loosen and remove the wheel cylinder. Once the old wheel cylinder is off, you can replace it with the new one. (note: some wheel cylinders are held in place by a snap ring).
Step 12 - Carefully start threading the steel brake line fitting into the new wheel cylinder. Screw it in as far as you can by hand making sure it doesn’t cross thread.
Step 13 - Insert the bolts into the wheel cylinder back on to the backing plate and tighten.
Step 14 - Next, tighten the brake line fitting into the wheel cylinder, make sure the brake master cylinder is full of fluid, open the bleeder valve on the wheel cylinder until brake fluid begins to drip, this process will eliminate any air in the system. Refill the brake master cylinder with brake fluid.
Step 15 - Tighten the bleeder and replace the brake shoes and hardware and brake drum. Make sure to have cleaned the drum and all components with brake cleaner.
Step 16 - If when the job is completed the brake pedal is spongy you may need to manually bleed the air from the brake system. Again, make sure the brake fluid is full. Have a helper pump the brake pedal four to five times, slowly. On the fifth time, have your helper keep pressure on the brake pedal.
Step 17 - While the pressure is on the brake pedal, open the bleeder valve, air bubbles and brake fluid should shoot out. Tell your helper that they should expect the brake pedal to go to the floor when you open the bleeder, but should not let off the pedal until you retighten the bleeder. If the brake pedal is allowed to raise with the bleeder open, it will suck air into the system and cause more trouble. Continue this process until only brake fluid is released with no air bubbles coming out of the bleeder. (note: continue to check the master cylinder to make sure it stays full while doing this process.)
Step 18 - Clean up all brake fluid and check for leaks. Make sure both the steel brake line fitting and bleeder valve are tight and not leaking.
Step 19 - Replace the wheel and torque it to the manufacturer’s recommendations, and adjust the rear brake shoes if needed. Replacing a wheel cylinder is a common job. A vehicle will fail state inspection if one is leaking. On average, one could expect to spend 150.00 to have the job done at a shop. However, the average part cost is usually under $30.00. It will take a little time, but the savings of doing it yourself is well worth it.
CAUTION: Brake fluid is corrosive. It has the ability to remove the paint finish from your vehicle. If it gets on your vehicle’s paint, wipe it off as soon as you can with a clean soft rag. Make sure to then clean the area with soap and water. Also, some brakes contain asbestos. Avoid using compressed air or anything to clean the area that will cause the brake dust to become air born. Make sure to wear a dust mask to help eliminate breathing in the dust.