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    • #56387

      I am rebuilding my brake calipers, on my 72 MGB. They were seized. I
      found that my brake old brake hose gave me the perfect connection to my
      air compressor air nozzle. Just remove the threaded tip on the average
      air nozzle, and the smaller male thread which threads into your steel
      brake line fits perfect. This allows you to use your air compressor to
      push out your brake pistons, with a perfect air line seal. BE CAREFUL,
      MOVE UP THE PRESSURE IN SMALL INCREMENTS, until you get a pressure that
      will move the pistons. Remember to put blocking in the space between the
      pistons, so you don’t push one out all the way without freeing the
      other. I had to move my pressure up to 125 psi to move one of the
      pistons. Tip courtesy of Tom Wiencek

    • #59008

      Having done this myself I can say that it works well but it is very dangerous!! If not protected by something, the brake pistons or master cylinder pistons will pop out and can fly across the shop and spray brake fluid all over the nice car in your garage or if you are really unlucky, they will hit you in the head. Wrap an old towel around the caliper or cylinder before applying air to it. Or use the grease gun technique-adapt a fitting to allow you to use a grease gun on the caliper/cylinder. Pump full of grease and the piston will come right out-and usually not fly across the shop either! Eric

    • #59066
      jumpinjan
      Participant

      I have to agree with Eric on this one. If your calipers are that rusty, why play with them with very high air pressure??? By the way, most of the better air guns have a rubber end that makes a good air tight seal, so you don’t need the old brake hose approach. Be safe!

    • #59627

      If you have really seized pistons,(Northern Style) pull out the Mig Welder and a hunk of Flat bar HRS !! . This is not necessary for the daily driver that has been in use, but for resurecting the dead, pop off the pads and grip the calipers in your bench vise. Slide the bar through the cavity opening and weld it to the piston protruding out. A piece of 1/4″ by 1 ” and 18″ long can give you enough leverage to turn (partial rotations work) and pull the piston out.
      Let me add that I spin my own pistons from Stainless and have never thought twice about using the original pistons a second time. It was suggested long ago by an expert not to seperate the caliper halves and keep the heat away from the castings because there are seals between the two halves.
      Tigger

    • #59629

      Well here’s my spin on piston removal. I have done the grease and air many times before I came up with a better mouse trap. It is true, necessity is the mother of invention. Although I’m sure I did not invent this approach, it felt like I did at the time. There had to be a faster, easier safer away. The big problem with air and grease it is difficult to get both pistons out without a frustrating effort. Air will not get the tough pistons out. And air and grease cannot be easily applied to both pistons.

      Here’s my process. Separate the calibers, drill a hole through the center of each piston and tap it with either a 1/4 inch or 5/16 inch tap. Pound the piston in to brake (pun intended) it loose then screw in a bolt and it comes right out. It takes less time this way than cleaning up the grease and dealing with “the other“ piston to get out. I never found a piston that would not come out this way. Actually, I came up with the idea when I couldn’t get one out with air or grease.

    • #59636
      quote Tigger:

      If you have really seized pistons,(Northern Style) pull out the Mig Welder and a hunk of Flat bar HRS !!

      I just experienced the worst & troublesome rusted calipers from a Tiger. I didn’t weld a bar to the pistons, I used a large SAE washer and pulled each piston with an internal bushing/bearing puller. You just need to show it whos the boss.

    • #59637
      mikephillips
      Participant

      I recently did a set by breaking them in two, heating then quenching each half. The quick thermal cycle broke the rust bond and out the pistons popped.

      Seal leaked to much to get pressure and I couldn’t get them to rotate in the bores until that I did this.

    • #60385

      I just went through this today. I was able to get air into the caliper to pop one out, I used a piece of cardboard between the two with a rag around it to keep it from shooting off.

      What to do with the second one, though? Well, the key was to secure one with some clamps and use enough air to get the other out far enough that it could be popped out using the lip for the dust covers.

      Yes, it’s loud, and not to mention that atomized brake fluid goes everywhere. So, be very careful and make sure you use all the protection, and something between the pistons to absorb the shock.

      I’ll find out in the next couple of days if I need to do it again.

    • #60386

      I just went through this today. I was able to get air into the caliper to pop one out, I used a piece of cardboard between the two with a rag around it to keep it from shooting off.

      What to do with the second one, though? Well, the key was to secure one with some clamps and use enough air to get the other out far enough that it could be popped out using the lip for the dust covers.

      Yes, it’s loud, and not to mention that atomized brake fluid goes everywhere. So, be very careful and make sure you use all the protection, and something between the pistons to absorb the shock.

      I’ll find out in the next couple of days if I need to do it again.

    • #60387

      Hi Pete,

      I don’t know if my previous response got to you so I will send another.

      <<it’s loud, and not to mention that atomized brake fluid goes everywhere>>

      That is why I recommend using a grease gun. The pistons quietly pop out without spray and flying missiles. Someone complained that it took a lot of grease and was hard to clean out but you don’t have to use just grease, you can first fill the cylinder with water, then put in the fitting and pump the grease in. Once one piston moves just a little, you can clamp it and then pump some more grease in until the second one moves.

      John Logan

    • #60394

      Thanks John, sorry for the double post, I evidently wasn’t logged in.

      I had to use the air method because I drove the car to a shop and had to drive it back out in a couple of hours as it’s the auto hobby shop on base. Otherwise, no ride home! So, I didn’t have the time or tools to put together a grease gun adaptor. But, that would be a much more controlled option of getting them out.

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