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Help - 348 Brake caliper/piston locked?

Discussion in '348/355' started by vdettore, Dec 5, 2018.

  1. vdettore

    vdettore Formula Junior

    Mar 3, 2017
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    If you’ve read a couple of my other posts you know I’m replacing my cv boots and also will attempt a rear wheel bearing on my 90’ 348. ( hopefully someone can learn from my mistakes ).

    I decided to crank my car since it’s been sitting a couple of weeks and out of habit pressed the brake pedal when cranking. As a result my left rear brake caliper engaged (it’s removed from the rotor but still hooked up to the brake line) and ...well it looks like I messed up a brake piston?

    The piston in the picture seems locked. It was actually a little cock-eyed. And brake fluids was everywhere. I tried compressing the piston( after removing the cap from the brake/clutch fluid reservoir) but it is not moving.

    Can anyone tell from the picture and my description what’s happened and what I need to do to fix it?

    Thanks for the help - yes I feel like an idiot
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  2. Wade

    Wade Two Time F1 World Champ
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    You aren't the first person to do that... many, I'm sure, since the beginning of hydraulic brake servicing. ;)

    Have you tried opening the bleed port and then resetting the piston?

    Don't be surprised if you'll need a caliper rebuild (but you might get lucky instead).
     
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  3. 97 Spider

    97 Spider Formula 3
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    How did you try compressing it?
     
  4. dahveedem

    dahveedem Formula 3
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    Take a breath.
    Like Wade said, break open the bleeder valve on the caliper itself.

    Then if you don't have a piston tool, put a fkat piece of something in there against the piston. Then grab a c-clamp and collapse that piston back in.

    A thought before you do that... check that piston sleeve ...and see if there are any cuts in it... if not maybe you just pushed the piston past the sleeve.. no biggie if not torn just push it back in.

    If torn.. if they are brembo calipers i have the rebuild part numbers you'll need. Its a messy job but easy to do.

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  5. vdettore

    vdettore Formula Junior

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    I opened the cap where you add the brake fluid. Then tried compressing it with a clamp. Didn’t budge. But I see from other replies I need to crack open the bleeder screw


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  6. vdettore

    vdettore Formula Junior

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    Oh man, thanks for the info. Couldnt figure out why the piston wouldn’t budge.


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  7. vdettore

    vdettore Formula Junior

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  8. m.stojanovic

    m.stojanovic Formula 3
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    If it still sits jammed in a slightly angled position ("cock-eyed"), use a thin longer piece of wood placed on the inside edge of the piston and tap it in the direction to straighten it up first. Tap carefully only until you feel slight sideways movement of the piston otherwise, if you hit it hard, you may jam it in the opposite angle.
     
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  9. Dave rocks

    Dave rocks F1 World Champ
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    You should be able to move it with a c clamp with bleeder closed. It might be mechanically bound. I would remove piston and look for damage (before it gets worst)
     
  10. vdettore

    vdettore Formula Junior

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    How do you remove the piston?


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  11. Dave rocks

    Dave rocks F1 World Champ
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  12. dahveedem

    dahveedem Formula 3
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    Just be prepared... when i rebuilt my calipers it was prolly the dirtiest job I've ever done. Brake fluid everywhere as i had a stuck piston and torn boot.

    If you back out the bleeder screw.. it may relieve some pressure and allow you to manipulate that piston. BUT Dave knows his stuff.. so definately get it out and look at it.

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  13. Dave rocks

    Dave rocks F1 World Champ
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    I should add that removing the bleeder is fine but jus be prepared to squirt fluid from it ;)
     
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  14. dahveedem

    dahveedem Formula 3
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    Nothing wrong with a little squirting... mine was a gusher.

    Like i said... I've done a lot of jobs.. this was the dirtiest...maybe put yourself and the caliper in a bubble when you throw compressed air at it.

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  15. pnicholasen

    pnicholasen Formula 3

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    First you need to put clamps on the 3 pistons sitting properly in the caliper, otherwise the compressed air will blow all 4 pistons out. Next put a piece of wood in the jaws of the caliper next to the jammed piston so the piston has a very limited travel ( like a 1/2" or so). Compressed air can violently blow the piston out and you want to control that so you don't damage the piston or yourself. Once the piston is out, live it up with brake fluid, then carefully line it up straight with the cylinder and work it back in. Once you get it started by hand you will need a clamp to GENTLY press it back in.
    Don't forget to turn the ignition key to accessory when you bleed the brakes.

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  16. pnicholasen

    pnicholasen Formula 3

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  17. fatbillybob

    fatbillybob F1 World Champ
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    Do not remove the piston because old seals swell. Removing a piston is a good way to violate your seal then you will have leaks once back in service. You may have already damaged the seal. If you pushed the piston just past the seal that is what is mechanically binding your piston. You may push the piston back with some force but you may also cut the seal and violate it. This does not happen with a new seal for a number of reasons. Sometimes the piston is just hard to push back by hand and you have done zero damage to anything. You just don't have a feel for how much force you need. You will most likely be just fine if you make sure the piston is square to the caliper and push it back in. On the other hand if the car is old or high miles seems like a perfect time to upgrade your old brake system to new by rebuilding the calipers with all new seals. What you want to do is remove caliper from all lines. place a wood or plastic strip between the multi pistons so that when the pistons are driven out they can't come out all the way because if you blow one piston out how do you blow out the others? So with strip in place you used compressed air in the caliper inlet hole and blow. Wrap caliper in towel to catch all the spray. Don't get your fingers between pistons or you will be in for some pain. Failure to wrap caliper in towel means you will get brake fluid in your mouth and eyes and anything within 20ft.
     
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  18. pnicholasen

    pnicholasen Formula 3

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    You probably already tried this, but did you try fitting which ever size socket fits fairly tight into the cup of the offending piston and gently tapping the end of the socket with a hammer at various angles to see if it will un-jam itself?

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  19. vdettore

    vdettore Formula Junior

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    Thanks all for the replies and help! I’ll be reading everyone’s replies later today or this evening.
    Quick question, brake fluid was all over the floor. Where did it come from?


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  20. Dave rocks

    Dave rocks F1 World Champ
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    The piston is either out of the bore or the angle is causing a leak. I would just get some new seals and rebuild it. You will need to check for piston / bore scoring.
     
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  21. krazykarguy

    krazykarguy Formula Junior
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    I also suggest rebuilding it at this point. The escape of the brake fluid indicates that the seal has been compromised. Due to age, it's likely too old and swollen to fit the piston back in without damaging it.
     
  22. yelcab

    yelcab F1 Veteran
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    I would get a kit and rebuild the caliper now that it is in this position. You were looking for more things to do, right? You are way over the slippery slope right now. From a CV boot to a wheel bearing and rebuilding calipers. Did anybody tell you that you have to open up the gearbox to re-stake the ring nuts? How about repack the flywheel?

    You are gonna end up with CV boot clamp tools, caliper depressing tool, circlip remover, brake bleeder tool. Christmas is here, get more tools. Don't forget the Wheel hanger tool, 200 ft-lb torque wrench, a set of Ribe sockets (don't ask where it is used).

    Sorry, I am not helping.
     
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  23. dahveedem

    dahveedem Formula 3
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    Here's link to the parts you'll most likely need for the Brembo caliper. Double your order of the boots cuz you'll invariably tear one in the process.
    https://www.ferrarichat.com/forum/threads/348-brembo-caliper-rebuild-kit-and-or-calipers.493271/

    And Paul is correct... with this "First you need to put clamps on the 3 pistons sitting properly in the caliper, otherwise the compressed air will blow all 4 pistons out."

    I didn't care as I was rebuilding the entire caliper so I just put a piece of wood in between the pistons so they didn't go bouncing around the garage walls like a crazy squirrel. I only used a 100psi crappy compressor and they popped out against the wood pretty hard.

    as to the crooked piston... if you open the bleeders and reduce the pressure you may be able to push the piston back with your fingers or a clamp. I'd probably just go ahead and rebuild that caliper at this point though so you can get that piston out and verify it's ok.

    The brake fluid on the floor is most likely a torn piston boot by the way... I know that because after I rebuilt mine I didn't realize I tore the new boot and found a puddle on the floor.. :(

    There's also a video somewhere on rebuilding the caliper but I can't find it right now.. .do a google search. Paul in the thread has made a bunch.. I can't recall if he made one for a caliper rebuild or not. BUT that tool I have posted is worth all the money.
     
  24. vdettore

    vdettore Formula Junior

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    I can get a used working caliper for $300. Would it be worth it? Or should I try to rebuild?


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  25. dahveedem

    dahveedem Formula 3
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    "working" for how long? if you are doing the CV boots yourself... you can easily tackle the caliper rebuild. I think my cost from Zeckhausen was less than $80 with shipping for both calipers.
     

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