Seized-Part Job · Car & Truck

How to Remove a Seized Brake Caliper Bolt

It has been clamped down for 60,000 miles. It is not letting go on the first date.

Caliper guide-pin bolts are small and usually come out with a ratchet. Bracket bolts are the problem: they are torqued high, often thread-locked from the factory, and sit right where road salt collects. Most "seized" caliper bolts are a mix of corrosion and thread locker, so penetrant and leverage beat brute speed.

The Method

Step by Step

1
Support the car and pull the wheel
Jack stands under a solid point, wheel off, steering turned so the bolt heads face you.
2
Clean the threads that stick out
Wire-brush the exposed threads on the back side of the knuckle. Penetrant cannot get past a crust of rust.
3
Soak from both ends
Spray the bolt head and the exposed threads behind the knuckle. Use a straw so it goes on the fastener, not the rotor.
4
Wait, then shock it
Give it 30 minutes minimum. Rap the bolt head several times with a hammer and a socket extension to crack the rust.
5
Break it with a 6-point socket and a breaker bar
Steady pull, not a jerk. A 6-point socket grips the flats instead of the corners. An impact wrench is fine here and often works better than a bar.
6
Clean, then reassemble to spec
Chase the threads, clean the rotor and pads with brake cleaner, and torque the bolts to the service-manual figure with the thread locker it calls for.

Heat call: Heat with care

Heat on the caliper body cooks the piston seal and the slide-pin boots. Only heat a bracket bolt if you are replacing the caliper and bracket anyway, and never with penetrant still wet on it.

Safety

Keep penetrant off the pads and rotor face. Oil-soaked pads do not come clean; replace them.
Clean the rotor with brake cleaner before the wheel goes back on, then test the brakes at low speed.
Never work under a car held only by a jack.

What to Spray