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Thread: Caliper Cylinder Should Push Out, Right?

  1. #1
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    Caliper Cylinder Should Push Out, Right?

    Hi all, 1995 525i 5SPD 280k

    My passenger rear brakes are locking up, I believe. I removed the caliper two days ago, pumped the brake pedal so that the cylinder would slide out so I can clean and lube up but, did not budge. It was difficult to press the cylinder into the caliper. Is the caliper toast, or should I attempt to pump the brakes until the cylinder eventually slides out and clean up and lube?
    I drive 60 miles a day and I can't drive it right now because it will start to smoke within 3 miles, which means that sucker is locked on that rotor and I do not want to warp the rotor.

    Thanks in advance.

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    Do you mean the allen head bolts that attach the caliper?
    These need to be unscrewed, pumping the brake won't do anything.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Rebuilt calipers are real cheap.
    demet

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    If you cant push the piston back in easily using a G cramp, you either inserted it an angle or it is seized. If in any doubt, replace calipers, rotors and pads. Bear in mind that a duff flexi hose can act as a one way valve and hold the brake on though

  5. #5
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    Thanks for the input. How can I bypass that caliper until I can get a replacement? I apologize. I meant piston, not cylinder, that's giving me a hard time. Obviously it will push out when I apply the brakes but, remains applied.I tried pushing the piston back in with a C clamp and it was difficult. Is it worth cleaning it up or should I just get a replacement? In the meantime, I still need to drive the car but, is there a way to bypass that caliper until I get a replacement?
    Thanks in advance..

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    Quote Originally Posted by drewusmaximus View Post
    Thanks for the input. How can I bypass that caliper until I can get a replacement? I apologize. I meant piston, not cylinder, that's giving me a hard time. Obviously it will push out when I apply the brakes but, remains applied.I tried pushing the piston back in with a C clamp and it was difficult. Is it worth cleaning it up or should I just get a replacement? In the meantime, I still need to drive the car but, is there a way to bypass that caliper until I get a replacement?
    Thanks in advance..
    Not any safe way to do this. Remans are cheap

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by ross1 View Post
    Not any safe way to do this. Remans are cheap
    I don't think I can get a reman by this weekend. Isn't there an end cap strong enough to cap the end of the brake hose? I'm assuming the Duff Flexi Hose is something I can use as a temporary fix but, not sure how that works.

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    Quote Originally Posted by whiskychaser View Post
    My apologies. Duff means defective. If the hose breaks down inside it may not allow fluid to flow back but holds the brake on. Dont drive with 3 brakes, even to the corner shop
    So basically, I'm SOL unless I pull out the piston, give it a good clean, reassemble, and hope that works? I was hoping there was a cap/plug that would screw on the end of the brake hose that connects to the caliper and hold the pressure in the hose.

    - - - Updated - - -

    something like this
    https://shop.advanceautoparts.com/p/...Fc0EDAodH_EB0A

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    I would much rather we talked about this in a few days than you drove around with 3 brakes. And as a result we couldnt.

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    Quote Originally Posted by whiskychaser View Post
    I would much rather we talked about this in a few days than you drove around with 3 brakes. And as a result we couldnt.
    Agreed but, I have to drive the car. Basically, either way you look at it, I'm stuck between a rock and a hard place

  11. #11
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    I understand your predicament. Calipers can be rebuilt at home... with a ~50% success rate if they're just leaking, and lower if they're seizing. Furthermore you'd need a piston seal kit; can't (= "really shouldn't even in the off chance it works") reuse the old seals. You need a new caliper. I can sell you one, but south42 is closer to you. Drive *CAREFULLY* , especially regarding following distances, and you can get away with two front and one rear brakes. As for how to accomplish that... standby...

    Two ideas, NEITHER OF WHICH ARE ENTIRELY SAFE AND I DO NOT RECOMMEND YOU ACTUALLY DO THIS. I am not responsible for what you do with your brakes or the consequences thereof. Capisce? Good. Now...
    1. Bypass fluid pressure. Disconnect the correct brake line from the ABS pump, attach to a hose that dumps back into the reservoir. You will spill brake fluid and the open cap will allow water ingress, so you'll need to flush them thoroughly (which you'll need after replacing a caliper anyway). Or...
    2. Bypass mechanical force. Remove the caliper and fasten as securely as you can to the trailing arm. Stick an object into it to block the piston from extending too far.
    Last edited by moroza; 10-12-2018 at 03:07 PM.

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    Quote Originally Posted by moroza View Post
    I understand your predicament. Calipers can be rebuilt at home... with a ~50% success rate if they're just leaking, and lower if they're seizing. Furthermore you'd need a piston seal kit; can't (= "really shouldn't even in the off chance it works") reuse the old seals. You need a new caliper. I can sell you one, but south42 is closer to you. Drive *CAREFULLY* , especially regarding following distances, and you can get away with two front and one rear brakes. As for how to accomplish that... standby...

    Two ideas, NEITHER OF WHICH ARE ENTIRELY SAFE AND I DO NOT RECOMMEND YOU ACTUALLY DO THIS. I am not responsible for what you do with your brakes or the consequences thereof. Capisce? Good. Now...
    1. Bypass fluid pressure. Disconnect the correct brake line from the ABS pump, attach to a hose that dumps back into the reservoir. You will spill brake fluid and the open cap will allow water ingress, so you'll need to flush them thoroughly (which you'll need after replacing a caliper anyway). Or...
    2. Bypass mechanical force. Remove the caliper and fasten as securely as you can to the trailing arm. Stick an object into it to block the piston from extending too far.
    Capisce! I appreciate the advice. Are there actual people out there that would fasten the caliper to the trailing arm and block the piston from expanding??? That is scary.. Can't I disconnect the hard line form the ABS and cap that connection? Wait!! My car has an ABS???

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    I'm hoping I can do something like this but, on a rubber brake hose.
    https://rennlist.com/forums/997-foru...ake-lines.html
    Go down the page and you'll see the design i'm looking for. I'm hoping someone tried this already on our cars.

  14. #14
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    Glad you appreciate that these are spooky propositions. Not to give you any ideas, but I once drove my Hilux up and down a meaningfully steep logging road with no brakes at all, just a handbrake that I never used (and would've done little as there was no bed either; two people could deadlift the entire rear off the ground). 4LO, tires at 10psi and I kept it at a crawl.

    All E34 except some early Euro strippers have ABS.

    The lines are going to be hard to cap because they're male at the caliper, male at the previous junction, and the one before that (soft hose between the body and the trailing arm) is hard to reach. You'll also need a bolt of the right thread pitch, which is slightly obscure (M10x1.0?). Now that I consider the implementations, I think that's your best bet, actually.

    Since you're likely going to the hardware store anyway, the Rennlist idea (female M10x1 fitting) is a good one too.
    Last edited by moroza; 10-12-2018 at 03:37 PM.

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    Quote Originally Posted by moroza View Post
    Glad you appreciate that these are spooky propositions. Not to give you any ideas, but I once drove my Hilux up and down a meaningfully steep logging road with no brakes at all, just a handbrake that I never used (oh and there was no bed either; two people could deadlift the entire rear off the ground). 4LO, tires at 10psi and I kept it at a crawl.

    All E34 except some early Euro strippers have ABS.

    The lines are going to be hard to cap because they're male at the caliper, male at the previous junction, and the one before that (soft hose between the body and the trailing arm) is hard to reach. You'll also need a bolt of the right thread pitch, which is slightly obscure (M10x1.0?). Now that I consider the implementations, I think that's your best bet, actually.
    I'll do my best to clean it up and order a reman. I once had an 87 accord, 5 speed with no brakes. only the parking brake. I had to drive 60 miles round trip to and from work on an interstate, slowing down with the gears. People behind me were not happy since I had to downshift quite early..

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    The only problem with that design is, it's a hard line that he is capping. I have to cap the rubber line to the caliper, which I think is a male end. So, a fitting like the one in the picture would work, if there is such a fitting that would match the thread.. it's time to take a trip to Ace..

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    I don't condone this but you could plug the abs ports to the rear brake(s). Use brake line from an auto parts store. Crush one end with a hammer on a hard surface and fold it over a bunch of times. Get into an accident with this kludge and you could be in very deep doodo.
    demet

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    Junkyard caliper for a temp?
    Considered just getting a rental car?

  19. #19
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    If the piston is backed off now, just compress the hose to stop the brake operating. Even vice grips will do that. And I will claim somebody stole my phone if you quote me

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    Don't be that guy. You are really asking for trouble by deliberately defeating your brakes. Not just your ass is in jeopardy either.
    You don't "have to" drive this car. Take a cab. Any parts store can get you a caliper in a day.
    Are you the guy that stops in the middle of the road when you miss a turn?
    Last edited by ross1; 10-14-2018 at 10:51 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by moroza View Post
    Glad you appreciate that these are spooky propositions. Not to give you any ideas, but I once drove my Hilux up and down a meaningfully steep logging road with no brakes at all, just a handbrake that I never used (and would've done little as there was no bed either; two people could deadlift the entire rear off the ground). 4LO, tires at 10psi and I kept it at a crawl.

    All E34 except some early Euro strippers have ABS.

    The lines are going to be hard to cap because they're male at the caliper, male at the previous junction, and the one before that (soft hose between the body and the trailing arm) is hard to reach. You'll also need a bolt of the right thread pitch, which is slightly obscure (M10x1.0?). Now that I consider the implementations, I think that's your best bet, actually.

    Since you're likely going to the hardware store anyway, the Rennlist idea (female M10x1 fitting) is a good one too.
    What appears to be illustrated here is an inverted flare union with a bleeder screw in it. Aside the fact that this is a profoundly stupid idea to begin with, a bleed screw has a male flare same as that union so there is no reliable seal there.
    Last edited by ross1; 10-14-2018 at 11:36 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by drewusmaximus View Post
    Hi all, 1995 525i 5SPD 280k

    My passenger rear brakes are locking up, I believe. I removed the caliper two days ago, pumped the brake pedal so that the cylinder would slide out so I can clean and lube up but, did not budge. It was difficult to press the cylinder into the caliper. Is the caliper toast, or should I attempt to pump the brakes until the cylinder eventually slides out and clean up and lube?
    I drive 60 miles a day and I can't drive it right now because it will start to smoke within 3 miles, which means that sucker is locked on that rotor and I do not want to warp the rotor.

    Thanks in advance.
    If you remove the piston you'll be able to sand off any corrosion on the calliper that's causing this issue. And also eyeball the piston to see if its still a perfect cylinder. You also need to see if the calliper pins are good. Its a good idea to get new ones they are cheap.

    If you need to, you should tie off both the rear brakes instead of just one wheel. Unbalanced braking is very dangerous.

    AFAIK 2/3, 3/5 or basically the majority of the braking force goes to the front wheels. If you are very conservative on turns, following distances , speed, and wet weather travel, you can probably live without the rear brakes for a short while.

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    You can also open the nipple on both rear callipers and pump out some of the brake fluid on that calliper alone by stepping on the brakes a few times then forcing the piston back in. Air will get sucked back in and basically that calliper will become a sponge. Then close the nipple. Or hell you could leave it open throughout. Brake pressure will go out the nipple and not push the piston out. Experiment with both methods and top off the reservoir while doing this.

    You're not going to loose the whole brake reservoir of fluid at all. Just imagine fluid in a long straw moving back and forth two inches . Anyway losing too much fluid is not an issue if you open the nipple and basically brake out some fluid from that calliper alone, then close. You will need to rebleed of course but you already had to do that when installing the new calliper.
    Last edited by alang1990; 10-14-2018 at 02:05 PM.

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    A reman rear caliper with hardware can be had for less than $40.....

    Why is this a thread?

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    Quote Originally Posted by zubbie View Post
    A reman rear caliper with hardware can be had for less than $40.....

    Why is this a thread?
    This^^
    To be fair to the OP he hasn't posted since the first day of this and ostensibly has repaired it properly by now.
    Some of the proposed solutions are, given the circumstance, absurd. More absurd is the willingness to contribute to this folly and that this thread will persist, so someone, someday may employ one of these methods as a repair and there will be bad consequences.
    I don't debate the effectiveness of(most) the proposed bodges, just the idea that the circumstances, convenience for the OP, call for it.
    Our OP isn't stuck in the middle of the desert without water. This car doesn't have to and shouldn't be operated on the road.
    I'm all for creative repairs and am proud of some that have gotten me by in a pinch. We are talking about brakes and there is no emergency here.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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