Frozen brake caliper piston

[Fly Mach .86]

One of the pistons on my 79 911 SC is frozen in the caliper. I've blocked the other piston and used compressed air to blow out the frozen one and it won't budge. Any ideas? What can I try next? Do you think the caliper will still be rebuildable when I finally get the piston out?
Cheers, Elliot

[Evans, Marv]

Eliot:
Sometimes you have to put penetrating oil in and let it set. Also you may have to take channel locks & clamp on the shoulder of the piston that pushes against the pad and try to rotate it back & forth to loosen it. This shouldn't damage the piston to where it isn't usable (but don't get too radical about it). Plus you can always buy used calipers and new pistons for not too much. After you get the piston loosened and with a C clamp on the other piston, try to blow it out. But, try to block them to where you blow them out in stages so you don't have one completely out with the other still down in the bore. Good luck.

[Fly Mach .86]

Thanks Marv,
I got some PB Blaster soaking in as I type.
Cheers, Elliot

[Dave Taylor]

Hi Elliot,

Just finishing with my brakes and I had some difficult ones. I used a c-clamp to squeeze the stuck piston back in a little ways, then hooked it back up to the car's brake system. I monitored as my wife used the brake pedal. I clamped the one that moved to put pressure on the stuck one and it moved right out. I had to adjust the clamp to keep it out of the way several times.

You may have to bleed the brakes to get the full pressure like I did.

Good Luck and watch your fingers!

PS...car has been sitting for 18 years, but the piston bores were perfect.

18 Years In Storage…1974 911
18 Years In Storage…1974 911

[ecm911]

I just rebuilt all my brakes on my 78SC. I agree with all of the above. Would add two points. I had to really crank up the air pressure on my compressor to brak one lose. One last resort, we were able to get one out use thsi metho - ntoice there is a small lip on the pistons. We were ablt to choax it out with a little persuaion with a wide cheisel and hammer.

Again becareful !

Earl

[Fly Mach .86]

I just now got the little sucker out. I was able to work it in and out a few times, clamped the other piston down, put some air on it and KAPOW! It came right out. Thanks for all the good advice.
Cheers, Elliot

[3.8RSR]

My tip:
Chizels not necessary! My thanks to my mate Don who suggested this when air would not move mine (about 12 years ago!) Ive never forgotten this I was so happy, after many days frustration with 4 seized calipers on my project 911.

If you're without compressed air, or air wont budge it, or if youre still stuck... try a hand GREASE GUN!

1. Disconnect caliper. Remove brake fluid from caliper. Spray in or preferably soak in WD-40 to penetrate for a few hours, in a container.
2. Try to carefully tap piston inward slightly to break the corrosion fusion. I used a socket of similar diameter to the piston and tapped this with a hammer gently and as squarely as I could. Move the piston just a few mm inward.
3. Loosen the caliper bleed nipple or replace with a new nipple if yours is corroded.
4. Attach and pump the GREASE GUN and build pressure gently and the power of hydrolics should do the rest!
5. Finish by washing out your caliper to disolve Grease, with petrol/solvent/cleaner etc and inspect your bores for corosion pits and damage.

Hope this helps someone someday!

[Joeaksa]

Bruce,

Totally agree! The grease gun method is a lot safer than cranking up the air pressure. You can really get hurt using air.

JoeA

[mike f]

I know I am resurrecting a really old post, but have this same problem. How do you connect the grease gun to the caliper? Or If I use air, the same question applies- how do I hook it up? Any pictures would be great.

[Eagledriver]

You might be able to screw in a zerk fitting where the bleeder screw goes. Take a bleeder screw into NAPA with you to match the size. You'll also need to block the line holes with a suitable bolt.

I prefer to push the calipers most of the way out with the brake pedal.

-Andy