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Caliper piston removal

Discussion in 'XJ Technical Chat' started by jag3, Oct 23, 2020.

  1. jag3

    jag3 Member

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    Ok. I made the number one mistake on my calipers. I unbolted them from forks and then thought, ok I will be replacing my brake lines with stainless from Len (they look fantastic), thanks xj4ever. Anyway I unbolted the lines drained the fluid, you know where I'm headed, yep, didn't push the pistons out. What a mistake. I got one out by pushing grease through it, that is the biggest mess ever, 3 cans of brake cleaner and still needs more, no more grease to push them out for me. I read from another post someone reconnected theirs to the short line from the MC. Bleed the line and there's no air in it but the piston only moves a millimeter then goes back in when I pull the lever. The piston is about one third of the way out but that's from wear. The piston that I did get out has so much dirt and crap stuck inside the piston seal tracks i hope i can get it clean, i did get brushes from Len to clean them, he has everything. Does anybody have any suggestions for removing the other piston and why it only moves a hair and then retracks?
    Thanks for your help.
     
    Last edited: Oct 23, 2020
  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    Squeeze the brake lover and open the bleeder valve. Release brake lever closed bleeder valve squeeze brake lever. Keep repeating this process. Next option compressed air just be advised the Piston will fly across the room.
     
  3. jag3

    jag3 Member

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    Thanks for the help. I did the brake lever and opened the bleeder and closed it and released the lever many times and all the air is out and no additional movement onthe piston. I don't have a compressor to try that route.
     
  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    There is a tool like a set of pliers that you insert into the piston squeeze and it expands to grab the walls of the piston to pull the Piston out oddly enough it's called a piston puller never used one but they're easy enough to find.
     
  5. jag3

    jag3 Member

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    Thanks for the idea. Another tool to add to the collection. Auto parts store here I come.
     
  6. cds1984

    cds1984 Active Member

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    I have a tool set that I use to pull pistons from the callipers.
    It is ...
    Well a really long bit of square rod that came from somewhere and a big long bolt (about 300mm long) that I found on the road one day and a spring (that has no use in this application as a spring) in between.
    I think it may be reverse chop sticks.
    At any rate once I stick that into a calliper piston and jiggle it out. It makes my day.
    I'll post a pic shortly.
     
  7. cds1984

    cds1984 Active Member

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    There you have it.
    That'll take any piston out!
     

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  8. jag3

    jag3 Member

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    Thanks. I dont have a rod but I was able to get the piston out. Since it was about a third out and I bleed them, but didn't work at first, I pushed it back in a bit to force any residual air back though the MC and bleed it a coulpe more times. That worked for me this time. Now another question. How long can I leave the calipers in Gunk Parts Cleaner? I dont care if the paint comes off because I want to repaint them and can i soak the Master Cylinder in it?
    Thanks for all the help.
     
  9. jag3

    jag3 Member

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    How clean do the piston seal guides need to be? Inside piston cavity not done yet. 20201025_113202.jpg Is this good or does it need to be better? Picture below (other side) is how it started. 20201025_112948.jpg Can I use 400 or 600 grit wet sandpaper on the pistons and piston cavity and on piston? Do the pistons look ok? 20201025_112905.jpg 20201025_112948.jpg
    I used a brass wire wheel from Len to clean the seal channels but used the small one in my dremmel tool but it spins so fast it chewed it up. I used the larger brush for the inner seal in my cordless drill at a slow speed and holds up great and works excellently.
     

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    Last edited: Oct 25, 2020
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    groves need to be spotless ( at least cleaner than you have them) so it does not deform seals. chacal sells little rotory brass brushes to help clean them of deposits.
     
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  11. Polock

    Polock Well-Known Member

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    that tan color stuff in the seal groove got to go. if you blow your propane torch over it, just for a second, it turns to dust and brushes right out.
    no need to get it hot, should be able to hold it the whole time
     
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  12. jag3

    jag3 Member

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    Tried the brass brush and can't get the one in the first picture any better. The caliper in the second picture I'll try the torch for a few seconds, I havent done anything with that one yet. Do you think it will work on the first one to get rid of the black stuff in the seal channels to get it cleaner?
     
  13. jpacman

    jpacman Member

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    Back on the topic if getting the piston out of the caliper: once I had the caliper on the work bench, I removed the air bleeder, wrapped the caliper in several shop towels, and used air pressure to blow it out. Apply air pressure to the air bleeder hole with an air nozzle with a rubber tip so it seals in the hole. The piston will exit the caliper with some velocity (you've created an air cannon) so be sure to block the piston from becoming a projectile. This method meant I didn't need any specialized tools and didn't need to pry or pull anything out.
     
  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    That works sometimes, but a grease gun works 100% of the time. The pressure that you can exert on the piston with air is far, far less than what can be exerted by a grease gun (a few hundred PSI with air vs. around 10,000 PSI with a grease gun), and the pressure drops off almost instantly once the piston releases from the bore.
     
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  15. jag3

    jag3 Member

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    Used the grease gun and that was a big mess cleaning the caliper afterwards but it did work. Also attached the short brake line to the other caliper and bleed the line and that eventually worked and less messy. Now it's how to get the pistons and calipers clean enough to rebuild.
     
    Last edited: Oct 25, 2020
  16. Timbox

    Timbox Well-Known Member

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    Take a good look at those pistons and make sure there is no nicks on them. Run your finger of them if you feel anything on the pistons, send them down. Those nicks will put a tear in the new gaskets you put in for the rebuild. If you have or can find a good polishing wheel, polish those pistons mirror clean. Keep up the good work.
     
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