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Technical How do you get pistons out of brake calipers?

Discussion in 'The Hokey Ass Message Board' started by WhitewallWill, May 22, 2022.

  1. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    20220522_141120_resized.jpg 20220522_141134_resized.jpg Rebuilding my calipers. Front end could have been sitting in the dirt forever before I got it. Front end is from a '86 Jag XJ6 so OT here but, belongs to the front of my 1965 F100. I've blasted the outside of the calipers. Bought stainless steel pistons and new seals. I split the caliper, because you can on these, then checked the small seal that surrounds a port going from one side of the caliper to the other. Gave each of the pistons a good smack to break them loose in their bores then bolted them back together and threw a rag between the caliper sides and gave them 90 lbs of air pressure to pop them out. No Go. What new or old world trick is there to get these pistons out? I can drop them in a bucket of Evaporust I guess but, hoping to get at these today.
     
  2. Budget36
    Joined: Nov 29, 2014
    Posts: 13,174

    Budget36
    Member

    Maybe a small hole and a slide hammer? Probably going to mar the surface of the bores up though.
     
    Flathead Freddie likes this.
  3. pwschuh
    Joined: Oct 27, 2008
    Posts: 2,827

    pwschuh
    ALLIANCE MEMBER

    That is odd. After they soak, maybe up the PSI to 120?
     
  4. FF8C2D53-446F-4E27-AED1-1EC2C8810426.jpeg When I would rebuild those calipers a grease gun pipe threaded into an air blower and it threads perfectly into the brake line hole.

    a 1/2” or so bit of ply wood so the pistons have something to hit against .

    and WATCH YOUR FINGERS !!!!! When the pistons finally decide to come out nothing will stop them and the fu)&ing hurt !!!!

    tapping around the calliper with a hammer helps to free them up as well .

    pistons , dust covers and seals are all readily available, hone the caliper . Clean everything and install “ wet” with brake fluid and your good .
     

  5. gary macdonald
    Joined: Jan 18, 2021
    Posts: 308

    gary macdonald
    Member

    If air wont move them , use adapter with grease gun . First separate halves , use wood or other to seal passages , do one half at a time and limit the amount the pistons can come out as to keep a seal if one piston doesnt move
     
    WhitewallWill likes this.
  6. deucemac
    Joined: Aug 31, 2008
    Posts: 1,483

    deucemac
    Member

    Trade them in and let the rebuilder worry about getting them out!
     
  7. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,245

    theHIGHLANDER
    ALLIANCE MEMBER

    If you smash a finger you soak it incider...:rolleyes:


    But seriously, if the grease thing isn't for you mix 50/50 acetone and standard trans fluid, not synthetic. Soak em good overnight or even a couple days. If that's not for you, heat and candle wax. Not too hot, just enough to get the wax to run around the edges and permeate the sides. Goes pretty quick, and candles seem better than straight parafin. let us know how it went.
     
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  8. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,719

    1971BB427
    Member
    from Oregon

    When I find problem pistons on brake calipers I dig the outside seals out first, and then blow them out with air. Often once the outer seal is removed I can spray some penetrant down around the piston and let it soak. Then they'll come out easy.
     
    WhitewallWill likes this.
  9. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    All sounded good dudes, thanks. Looking at my pile of debris I ended up popping the seals off and blasted them with Sea Foam. After swearing at them I'm onto another task. F'in calipers!
    20220522_154313_resized.jpg
     
    VANDENPLAS likes this.
  10. BE CAREFUL WITH AIR!!! Those things will come out like a fucking bullet!! Try adapting a grease gun and pump them out. Lots of cleanup afterwards, but safe!
     
  11. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    I'm with you man. I stuff a rug between calipers after bolting together and shoot them. 90 psi is my limit, not the compressor's.
     
    Black Panther likes this.
  12. deathrowdave
    Joined: May 27, 2014
    Posts: 3,519

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    This is a total force , physics issue . Area of the piston x the pressure applied to the piston is the total psi force applied to the piston . Believe me it will hurt you terribly , use caution and up most safety . Brake fluid alone to the eyes is not a good way to loose vision
     
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  13. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    Like the joke goes, when the old ranch hand couldn't find the emasculators he sends the young ranch hand to go find a couple of good sized flat rocks. The young ranch hand says, jeebuz man, won't that hurt? and the old guy replies, "Only if you get your thumbs between the rocks".
     
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  14. I've always used a grease gun on the really stubborn ones. The zerk adaptor will usually fit right onto the bleed screw, just start pumping grease into it. One advantage over air is the grease isn't compressible so no worries about the piston flying out at high velocity; it'll only move by the amount of grease injected. With multiple pistons, once one is most of the way out, put a clamp on it so it won't come out more then start in with the other one. Like is said, it leaves a mess but there's no smashed fingers or other damage. If they won't move with a gentle squirt of air, more air usually isn't a good idea...

    As to the condition of the piston bores, if the main seal fits in a groove in the bore, hone to get the lumps out but that's all you really need. If the main seal fits on the piston, then a damaged/pitted bore generally means a new caliper or a sleeve.
     
  15. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    Always have ear plugs and safety glasses on. I'm a house builder by profession. Need to be in one piece to put viddles on the table.
     
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  16. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    Will switch to grease! Good idea.
     
    Tow Truck Tom likes this.
  17. clem
    Joined: Dec 20, 2006
    Posts: 4,188

    clem
    Member

    Seems that I am the only one that uses a pair of vise grips………..:eek:
     
    Desoto291Hemi likes this.
  18. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    Tried this. These puppies are stubborn. Also 4 piston calipers, if one pops and the others don't the show's over. Have them soaking now in the sea of the foam.
     
    clem likes this.
  19. B.A.KING
    Joined: Apr 6, 2005
    Posts: 4,039

    B.A.KING
    Member

    Grease, you can move the world with hydraulic, if you can hook it up.
     
  20. deathrowdave
    Joined: May 27, 2014
    Posts: 3,519

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    You can move the world with hydraulics if you have something to push against
     
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  21. lostone
    Joined: Oct 13, 2013
    Posts: 2,820

    lostone
    Member
    from kansas

    Put a penetrating fluid in them thru the brake hose hole, let them soak for a while. After a day or 2 pour it out. Put a 1x4 or if enough room a 2x4 piece of wood in between the pistons and apply air. The wood will catch the pistons and keep them from flying out of their bores and no worry about getting hit with anything.

    The board trick works great. Literally done 100's that way.

    .
     
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  22. Beanscoot
    Joined: May 14, 2008
    Posts: 3,056

    Beanscoot
    Member

    It might be kind of late now, but I'd disconnect a front brake line on my car and rig up a line to the assembled caliper. Put a spacer between the pistons and pump the brakes to push out the pistons. Once they've come out half an inch or so the rest should be easy.
     
    brEad, Happydaze, RmK57 and 1 other person like this.
  23. Harv
    Joined: Jan 16, 2008
    Posts: 974

    Harv
    Member
    from Sydney

    When using air, run the airline outside. Don't blow pistons out inside the shop. When they let loose, they either spray brake fluid or dribble it. Murphy's Law says that spray of brake fluid will find the nearest painted surface. A small amount of brake fluid on the concrete outside the shed is no big deal. A small amount of brake fluid on your freshly painted car will induce a coronary.

    Vandenplas' wood packer idea works. Make the packer thick enough (a couple of layers of ply or a pine offcut) that the pistons can't escape, just move a bit. Once they have broken free, user lower air pressure and fewer/no packers to drive them out.

    Cheers,
    Harv
     
  24. brading
    Joined: Sep 9, 2019
    Posts: 704

    brading
    Member

    You could push them out using a bench mounted M/C connected up to the caliper I have done this. Or you could connect a pipe up from your car M/C.
     
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  25. When I used air in the shop, I always put a plastic pail over the caliper in case a shower of brake fluid came with it. A small cardboard box works.
     
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  26. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,778

    Moriarity
    SUPER MODERATOR
    Staff Member

    when I was a mechanic back in the 1900's (70's and 80's)I would push them out with the master cylinder, before I disconnected them from the car
     
    brEad, winr, Mr48chev and 6 others like this.
  27. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    Whoa Ho! My set up is right beside the truck. Think I might try this before the grease, the cleanup could be a bit simpler, thanks.
     
  28. I made an adaptor to fit onto a hydraulic porta-power, just have some clean undies handy when they let go!
     
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  29. WhitewallWill
    Joined: Mar 5, 2014
    Posts: 645

    WhitewallWill
    Member
    from N. Van, BC

    The cleanup might be simpler I said. Reminded me of a friend's dog story. He had 2 of them, a Jack Russel and a Burnese Mountain dog, and a new BMW. Ripped into the Liquor store and came out to see Roscoe, the Jack Russel, up on the package tray but, obscured in the back window. Opened the door to find the Burnese had an unfortunate but, explosive ass hammering diarrhea session. Not sure Roscoe among other things was ever the same.
     
    Algoma56 likes this.
  30. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,719

    1971BB427
    Member
    from Oregon

    If you have a block of wood to stop piston travel it will also avoid the issue of one coming out, and the other stuck still. Once both have come out against the block of wood you can then hit it with air again, or grab the piston with large channel locks to pull them. Usually come out easy once you've gotten them to move a little.
     
    winr, Happydaze and sunbeam like this.

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