Frozen Brake Caliper

How am I supposed to get THAT out? When that question comes up, an argument takes place in my brain. Half of my brain tells me I can’t do it, the other side is all can-do. The pessimist side telling the optimist side I can’t do something is like telling a dog he can’t sniff trees and fire hydrants. If you are like me, I like figuring difficult things out.

Screen shot 2013-11-04 at 2.57.32 PMI’ve been refreshing a 78 Midget that hasn’t been on the road in well over a decade, maybe two. Now that I have the painting done, I’m taking my time putting it all back together, renewing components as I go. Today’s project was to revive the front brake calipers. Initial inspection revealed that the brake pads didn’t have very many miles on them. Apparently, since replacing the pads the outside half hadn’t moved. Now it was frozen. Sitting for an additional 10+ years didn’t help this condition. Here lies the problem. How do you get that piston out of there when it is fully pressed back into the caliper half? There isn’t anything to get a hold of. I even popped the first seal out so I had at least a little something to grab, but nothing doing, that caliper was stuck in there tighter than a seat on United Airlines. Not only that, there are warnings in the manual not to separate the two halves, and there’s a reminder of that fact in the Moss catalog if you try to buy the little o-ring needed to put them back together again. So, in my mind there has got to be a way to get that piston out. The inner side has a hole where the pressure line connects, you can use a 5/16-inch dowel rod to push that piston out. And there may be a special tool out there but I don’t have it and don’t want to buy one for just one job.

Screen shot 2013-11-04 at 2.58.00 PMIf the caliper was still on the car I could just restrain the inner piston and just use brake pedal power to push the outer piston out. In fact I thought of that, but when I pulled the master cylinder out of the storage box it was so rusted and corroded up it looked like it had been lying on the ocean floor for 75 years, complete with barnacles. I had ordered a replacement but I didn’t expect to see it for another 4 or 5 days. That just wasn’t a viable option at this stage of restoration.

Then it occurred to me that I could still use fluid pressure to pop that piston out so that I could clean and renew the seals. I inserted a 5/16-inch dowel rod through the pressure hole and tapped the inner piston out till it was even with rotor slots in the caliper. Then I removed the caliper from the vise and set it on my bench with the pressure line hole facing up and topped off the brake fluid.

Screen shot 2013-11-04 at 2.58.32 PMNext, I used the copper washer from the pressure hose, a regular washer and fine thread 3/8-inch X 3/4-inch bolt to plug the pressure line hole. Now I had a caliper solid full of fluid and sealed off so nothing could escape. I put it back in the vise.

I used two c-clamps and applied pressure evenly on both sides of the inner piston by tightening the clamps simultaneously. The idea was that by compressing the piston on the inner half it will put pressure on the outer half to push it out

It took some serious pressure but it finally started to move. Success! Take that pessimist side of my brain! Victory.

By Jere McSparran


'Frozen Brake Caliper' have 8 comments

  1. December 14, 2013 @ 5:22 am Jonathan

    I had similar problem with my 66 Healey. I ended up installing a grease fitting where the bleed screw goes. Then using a grease gun I filled the caliper with grease forcing the pistons out. (Do not use air pressure. This can send the piston shooting out at a dangerous rate!)


  2. December 15, 2013 @ 4:14 am Andy O

    Sorry I think it’s great that you were able to get out the piston to solve your problems but if i am restoring my car ,new calipers in the brake system are a must, always remember in any project SAFETY is a #1 concern


  3. February 14, 2014 @ 6:29 pm Sean O

    Andy, why do you equate ‘rebuilding’ with ‘unsafe’? Can you please provide some evidence to support that position? What if the technician who assembled your new caliper had a ‘bad’ day? For me, safe is when I know that it was done right. By the way, can I have your old ones? :)

    Jonathan, thanks for sharing your brilliant idea. I used it to successfully remove two very stuck pistons. While the pistons are toast, fortunately the calipers are in very good shape and are perfect rebuild candidates. Instead of using a bolt, I used the bleeder from the rear wheel cylinder (which I am replacing Andy). I also had switch from c-clamps to two bench vises to get the last piston out. I placed the caliper between the two vises and inserted foot long crow bars – one behind and the other through the caliper. The vises made short work of it. No damage and no mess. Thanks again.


  4. June 22, 2014 @ 5:40 pm Wes gray

    Whenyou know you’ve done it right. Yes… Rather than someone you don’t know at all.
    Many years ago my jousts with MGA and Dunlop disc brake calipers… The folks at BMC
    In SF nought I was daft, thinking I could buy the caliper middle fluid transfer seal…
    The caliper halves were the most perfect machined surfaces… In addition to just putting back the original seal since could not get it… I used the then newish permeates 2000 pink beads that compresses to thin plastic when pressured…
    Figuring things would self seal, maybe never come art again. Tightened down the half securing bolts
    Drove that car another ten years, never a bit of trouble from front calipers… Almost fun…


  5. June 24, 2014 @ 8:39 am Michael C. Papadopoulos / owner of MICCI

    An much easier way is available, but it ( is not for the ” Know it all people ” !.!.!.), for the asking.
    MICCI ( MCP, or call 630-898-2560, Leave name, Ph. #, short message.
    No solicitations please.( FYI, 53 years on Brit/Euro classics.)


  6. April 17, 2016 @ 6:08 am Mike Sutton

    i have a 1966 BJ8 that the brakes are sticking.I have rebuilt calipers and replaces brake master cylinder to no it the rubber brake hoses or the servo?


    • October 29, 2019 @ 3:11 pm Keith P.

      I had he same problem with a front brake on my 71 TR6. I rebuilt the caliper, but still locked up. So I replaced the caliper and disks, but still locked up. It was the rubber brake lines. They get squishy inside and let the fluid flow toward the brake, but not back out, thus locking the brake. Stainless steel braided brake lines solved the problem.


  7. February 6, 2017 @ 4:54 pm James Vierra

    Hello, I just bought two new calipers for my 1978 B. Next to the bleeder screw is the head of a small bolt. What is this and what if anything should be done with it.


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