Wheel Cylinder: Fundamentals and Basics

REMOVAL
- Wheel cylinder retaining bolts, brake line fittings, and bleeder screws are often heavily corroded. Prior to starting the job you should spray these with a penetrating oil.
- A line (flare nut) wrench should be used when loosening the brake line fittings. These fittings round off easily.

OVERHAUL
- Light amounts of corrosion within the cylinder bore and on the piston may be removed with crocus cloth.
- Pitting and heavy corrosion should be removed with a hone. When honing the hone should be inserted and withdrawn quickly to achieve a 45 degree crosshatch.
- Closely inspect the areas of the cylinder where the pistons seals contact. It is very important these areas are absolutely free of deposits, corrosion, or pitting.
- Remove the bleeder screw and verify that the passage is clear.
- Leave the bleeder open when installing pistons and cups into the cylinder bore. If the bleeder is closed a large amount of air will be forced into the brake lines.
- Use brake assembly lubricant to coat the cylinder bore, pistons, and cups. Clean brake fluid is an acceptable lubricant when assemblying the wheel-cylinder but brake assembly lubricant is much slicker and minimizes the chance that the cups will be damaged.

WARNING: Do not use a petroleum based grease or oil to lubricate the wheel-cylinder components. This will cause the seals and cups to swell and deteriorate.

- When reassemblying the wheel-cylinder it is helpful to follow this sequence:
1. Rear cup (verify the cup is inserted properly, flat side towards the piston, concave side towards the center)
2. Rear piston
3. Rear dust cap (this prevents the rear cup and piston from popping back out when the spring and front components are installed).
4. Spring
5. Front cup
6. Front piston
7. Front dust cap

INSTALLATION
- Attach the brake fluid line fitting loosely to the wheel-cylinder prior to inserting and tightening the retaining bolts. The brake fluid line fitting is much easier to attach and start turning with the wheel-cylinder loose.

WARNING: Don't forget to tighten the brake line fitting after the retaining bolts are tightened.

- Leave the wheel-cylinder bleeder screw open and place a drip pan under the rear brake assembly. Refill the master-cylinder with new brake fluid and let the fluid gravity bleed through the open bleeder screw. When brake fluid begins to drip from the bleeder, close the bleeder screw.

NOTE: The brake system will still need to be flushed and bled, but this makes starting the process much easier.