From digest.v7.n140 Tue Aug 19 14:08:41 1997
From: Bob Stommel <bob_at_trader.com>
Date: Tue, 19 Aug 1997 12:28:46 -0500 (EST)
Subject: How to rebuild brake calipers

[I just sent the following message in response to a fellow Digester and thought that others might be interested. The is the procedure I use -- it may not be the best, but it works for me. If anyone has an easier one, please post it.]

Get a factory caliper rebuild kit from the dealer or one of the Roundel mail order vendors. They run about $13-20 per caliper depending on the model. The kit includes the internal piston seal and the outer dust boot.

Here's the procedure:

1. Remove caliper. Remove brake pads.
2. Place a piece of wood between the piston and the caliper end and using compressed air (around 30 psi), force the piston all the way out of the caliper. The dust boot will come with it.
3. Remove the piston seal from inside the caliper.
4. Remove the brake fluid bleed nipple and spray down the entire inside of the caliper with brake cleaner and let it dry completely. You may have to use an old toothbrush to get all the crud out of the inside of the caliper. Clean the piston the same way. If there is stuff clinging tenaciously to the piston, use a Scotchbrite pad the clean it off.

[Before doing the next steps, make sure that your hands are surgically clean and that your work area is almost the same. Any dirt that gets into the caliper will cause you headaches later.]

5. Soak the caliper seals and dust boots in clean brake fluid.

6. Install the new piston seal in the caliper. Coat the inside of the caliper with lots of clean brake fluid.

7. Coat the piston with clean brake fluid.

8. Place the dust boot over the INNER end of the piston with the "lips" of the boot facing the caliper cavity and hanging over the edge of the piston. Press the lips of the dust boot into the groove inside the caliper cavity. Push the piston into the caliper -- this will take some effort as the new seal will be very tight. The piston WILL go in -- just be patient and make sure the piston is abolutely straight as you push on it.

9. Replace the bleed nipple, but don't tighten it.

10. Force brake fluid into the caliper through either the nipple or the opening for the brake line until fluid comes out the otter hole (if you don't know which hole is the otter hole, ask Duane Collie). This will "prime" the caliper so that bleeding it will be easier.

11. Reinstall caliper, brake pads, etc.

12. Pressure bleed the system. (Steve D'Gerolamo sells a neat metal cap for this that attaches to the brake fluid reservoir.)

Bob Stommel
Indianapolis