How to Replace Your Wheel Cylinders
What you will need:
- Line wrenches
- Socket set or wrenches
- Jack and jack stands
- Drip pan
- Fresh brake fluid
- Brake cleaner
- CRC 5-56 or similar
- Wheel cylinder hone
- Rubber gloves (Optional)
Why replace your wheel cylinders?
After a period of time the wheel cylinders will start to leak. When they do the braking force will diminish and, in extreme cases, could cause loss of braking. You probably won't know something is wrong until you notice the pedal is a lot lower than it used to be, or it slowly sinks as you hold it. If you have your brakes inspected at regular intervals, a leaking wheel cylinder will be caught before it has a chance to ruin your brake shoes.
There are two ways of dealing with a leaking wheel cylinder. One is to replace it, the other is to rebuild it. Neither one is really difficult to do. It just requires a little work and a couple of things to keep in mind as you do it. The choice to rebuild or replace is dependent on a couple of things. Usually it is faster to just replace the wheel cylinder. Another factor is the bleeder screw may be so deteriorated that opening it is impossible. That makes replacement the only option. Rebuilding is cheaper, but takes longer to do.
Before you start:
Follow these instructions carefully. Read and be sure you understand them before you begin.
Gather together all of your tools and supplies before you begin. Allow plenty of time to do the job so you don't have to hurry.
Remember that these are general instructions. For more detailed instructions pertaining to your specific vehicle, consult an appropriate repair manual.
Safety is important whenever you're working around machinery. Beware of hot objects, sharp instruments and hazardous materials.
Don't substitute tools unless you're sure you won't compromise either your safety or the performance of your vehicle.
Never work on a vehicle that is only supported by a jack. Use jack stands to support the vehicle while you work. Work on a solid, level surface. Never jack a car up on dirt or grass.
Okay, let's put on some old clothes and get to work. Make sure that your car is parked on a level grade, rather than on any sort of hill or inclined driveway. Jack up the car and place your jack stands under the frame to support the vehicle. Block the wheels to prevent rolling. Make sure the new wheel cylinders are the same as the ones you are replacing. Most are interchangeable left to right, but some are for the left or right sides and can't be swapped around. And don't forget, wheel cylinders are replaced or rebuilt in pairs. If, for some reason, one side can't be rebuilt, then replace both. Don't rebuild one and replace the other.
REPLACING WHEEL CYLINDERS:
Jack up the car and place jack stands under the frame to support the car. NEVER work on a car supported by the jack alone.
Remove the tires, brake drums and brake shoes. If the brake shoes are soaked with brake fluid, replace them. Mark the drum to the hub so you can replace it the way it was.
Spray the hydraulic line and fitting with CRC 5-56 or a similar rust penetration spray. You might want to do this first so it has time to work. Put your drip pan underneath it to catch any over flow and brake fluid.
Using the appropriate size line wrench, loosen the hydraulic fitting. I recommend a line wrench because they are designed specifically for working on hydraulic fittings. A standard wrench will work, but the chances of ruining the fitting are greater. Don't try to turn it out in one shot, work it back and forth and spray some CRC 5-56 on it as you work it out. This will keep the line from twisting as you remove the fitting.
Before you take the fitting off completely, remove the two mounting bolts. Then take the fitting off by hand and remove the wheel cylinder. You do this to avoid any possibility of bending the line. As soon as the fitting is off, brake fluid will start to run out. Plug the end of the line with a suitable plug, I use a piece of vacuum line with a bolt in one end.
Note: Some cars use clips or snap rings to attach the wheel cylinders. Most notably GM vehicles. Some applications require special tools to remove and install them.
Now that the fitting is off and the old wheel cylinder is out, you can install the new one.
Start the fitting in the new wheel cylinder and turn it is as far as possible by hand. Then mount it on the backing plate and install and tighten the mounting bolts. Don't go crazy here; you don't want to snap the bolts off.
Once the mounting bolts are tight, tighten the hydraulic fitting.
When you have both wheel cylinders replaced, open the master cylinder and fill it with clean, fresh brake fluid. Then open the bleeders on the wheel cylinders, one at a time, and close them when you see a steady stream of fluid coming out.
Reinstall the brake shoes and drum. Adjust the brakes and then bleed the wheel cylinders. Have someone hold pressure on the brakes and make sure there are no leaks.
And that's it; you're done. If everything goes smoothly it will take about an hour a side to do, including the bleeding.
© 2001 Vincent T. Ciulla