DIY: Replacing Brake Wheel Cylinders

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.

Rebuilding Wheel Cylinders:

1. Do steps 1 and 2 above.

2. 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.

3. Using the appropriate size box wrench or socket, Loosen the bleeder screw. I would use a socket if possible; it grips the bleeder screw much better. If it is hard to turn, you can try tapping it with a small hammer. Some times this will break it loose. Don't it too hard or it may become damaged. If it does break you will have to replace the wheel cylinder.

   Note: Most times the wheel cylinders can be rebuilt without removing them. On some cars you will need to remove them. If you have to remove them, follow the procedure as outlined above.

   Disassembling Wheel Cylinders:

4. Pry boots away from cylinders and remove.

5. Press in on one piston to force out other piston, cup, spring -- with cup expanders -- cup and piston. Do this with the bleeder open so you don't force air into the hydraulic system.

6. Wash wheel cylinder, pistons, and spring in clean brake fluid or brake cleaner. Clean thoroughly and blow dry with compressed air. Do not use a rag as lint from the rag will adhere to bore surfaces.

7. Inspect cylinder bore and piston for scoring and pitting. Wheel cylinder bores and pistons that are badly scored or pitted should be replaced. Cylinder walls that have light scratches, or show signs of corrosion, can usually be cleaned with crocus cloth, using a circular motion. Black stains on the cylinder walls are caused by piston cups and will not impair operation of cylinder.

8. Using a drill and wheel cylinder hone, hone out the inside of the wheel cylinder. Move the hone fairly quickly, you want about a 45-degree angle to the hone pattern.

   Assembling Wheel Cylinders:

9. Before assembling the pistons and new cups in the wheel cylinders, dip them in clean brake fluid.

10. Coat cylinder bore with clean brake fluid.

11. Install expansion spring with cup expanders in cylinder. Install cups in each end of cylinder with open end of cups facing each other.

12. Install piston in each end of cylinder having the flat face of each piston contacting the flat face of each cup, already installed.

13. Install a boot over each end of cylinder. Use care not to damage boot.

14. 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.

   To rebuild both sides will run about three hours including bleeding.

   Before you decide to replace or rebuild, get prices for a new wheel cylinder and a rebuild kit. You may decide the price difference is not worth the extra work. At random, I checked the price of a wheel cylinder for a 1991 Chevrolet Camaro RS. A new wheel cylinder is $61.50 (OEMSRP). The price of a rebuild kit is $29.25 (OEMSRP). In this case rebuilding would save you over $60.00.

_{Additional Information provided courtesy of ALLDATA DIY}

   _{Copyright © 2000 - 2003 Vincent T. Ciulla All Rights Reserved}