It’s frustrating for the do-it-yourself or seasoned mechanic to be confronted with stubborn caliper bolts during a routine brake repair. Since there are hundreds of caliper styles and different caliper bolt applications, it can become a challenge, even with a stocked tool box. While there are a few tricks that can help, patience, knowledge and the right tools are the best ways to free the bolts without breaking them.
1. Spray the caliper bolts with penetrating spray and allow the lubricant 10 to 15 minutes to soak in. If applicable, remove the rubber boots covering the bolts by gently prying them off.
2. Choose the suitable sized socket, hex-head bit or Torx-head bit to remove the caliper bolts. Attach the tool to a breaker bar and try to remove the bolt. Do not use excessive force if the bolt does not break free.
3. Light up the torch and apply heat along the inside edge of the caliper housing where the caliper bolt sticks out. Be sure all the rubber boots have been extracted or you will damage them with the torch. Do not heat the head of the bolt; just the caliper. Keep the torch away from the bleeder screw and the caliper piston. If necessary, also heat the housing of the caliper that embraces the entire length of the bolt.
4. Apply the breaker bar and suitable tool to the caliper bolt and try to break it free again. In the event the caliper bolt head strips, pound a bolt extractor onto the head of the bolt and use a suitable sized socket to mate to the end of the extractor.
5. Repeat Step 3 as often as necessary in order to break the internal corroded seal of the bolt. The hotter the caliper housing gets, the better chance of success for stubborn bolts. Once the caliper housing is red, apply Step 4 again in order to break the caliper bolt free. Once the bolt is ready to come out, you will hear it squeaking as you turn it counterclockwise. Reheat as necessary until the bolt is freed.
6. Drill or hone the caliper bolt hole in order to clean the internal corrosion that caused the bolt to seize. Use a suitable sized drill bit to match the diameter of the bolt. Some floating calipers may need to have the internal slides removed in order to properly re-lubricate.
7. Bring the old caliper bolt to the bench grinder and clean the surface and threads off using the wire brush wheel. In the event the caliper bolt was compromised in the extraction process, replace it with a new one.
8. Apply a coat of anti-seize compound to the slides and/or the smooth shoulder of the caliper bolt. Reinstall when desired and torque the bolt to the specifications of the manufacturer.