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  #1  
Old 04-10-2016, 07:30 PM
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caliper will not retract pad

Over time, my driver side caliper would not retract and stay in contact with the rotor. Finally it pretty much locked up and would not release.
What I've done:
1. New rotor and pads
2. Replaced the hose to the caliper.
3. Bleed with a griots garage brake vacuum bleeder. Master cyclinder never went below min line.

The caliper would still not retract. The caliper would not retract when I cracked open the bleeder valve. Does this mean there is air in the line somewhere?

4. Installed a new reman caliper, bled it again and still same issue, won't retract.

Any ideas? Thanks!

Last edited by vstech; 04-11-2016 at 02:12 PM.
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  #2  
Old 04-11-2016, 01:31 PM
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Different poster response. Your caliper is bad. The presence of air in the system is not relavent. Piston or pistons stuck on with the bleeder open is a bad caliper.

As for the actual piston retraction. Normally in operation it is only a slight movement back from the disk.

Welcome to the site. You perhaps should have started a new thread though.
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  #3  
Old 04-11-2016, 02:15 PM
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Welcome to the forum!

first off, what year and model car are we discussing?

I moved your post and created your own thread, as your situation is not the same as the other thread OP.

it sounds like a piston or sleeve in your caliper is shot.

time for a new or a PAIR of remanufactured calipers. DO NOT install a single reman on the front of these cars... a single NEW is fine, if you know the other side is original.

change all the hoses while you are at it, and flush out all your fluid with fresh fluid. old fluid absorbs water from the air, and it collects in the lowest points... the caliper pistons.
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Old 04-11-2016, 02:27 PM
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For those that don't know, the only thing that retracts caliper pistons is a slight rotation of the square O-ring. There is no spring return. It works amazingly well, but only if the piston is free to slide. Some of the earliest front calipers on 60's Mustangs and Darts would get stuck from rust, which is how after-market Stainless Steel Brake Company got their start.
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  #5  
Old 04-11-2016, 07:59 PM
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From what I understand, this is common when a car of our flavor sits. I need to replace both front calipers on mine. They stick more than they should, but the car is drivable.
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Old 04-11-2016, 08:11 PM
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Quote:
Originally Posted by BillGrissom View Post
For those that don't know, the only thing that retracts caliper pistons is a slight rotation of the square O-ring. There is no spring return. It works amazingly well, but only if the piston is free to slide. Some of the earliest front calipers on 60's Mustangs and Darts would get stuck from rust, which is how after-market Stainless Steel Brake Company got their start.
I understand that the piston seal is supposed to retract the pads slightly, but in my experience it does not. It is common to have the pads drag on the disk when one turns the wheel by hand. This is normal. The pads are pushed back a bit by the bearing run out on the first few corners one takes after releasing the brakes. If you want to spin the wheel with out having the pads drag, you can kick both front and rear of the tire. This will push the pads back enough to allow the wheel to spin, but it takes a very firm kick.
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Old 04-11-2016, 08:36 PM
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Thanks for the replies and ideas, very much appreciated. I didn't realize when I did my google search for stuck caliper that this was a thread in a Mercedes based forum so I appreciate the help.

It is my dads old work truck, 1994 Mazda B3000. As Barry mentioned, now that I was able to watch, the caliper does retract ever so slightly. Slight friction and turns with a little drag. The odd (to me anyway) of those hammer in caliper clips you tap in (not the bolts I'm used to working with). I replaced the passenger side caliper and brake lines. Bled it from the back to front and it seems to be working now. The one thing I did was on the clip, I might have hit them in to far instead of centering it so the outer pad glides, but gives the inner fender wall side where the caliper is, room to retract slightly.

I'll know for sure tomorrow as I only test drove it down around the neighborhood and back...road test tomorrow to see if it's fully good to go.

Thanks again for the advice and troubleshooting ideas!

Tim
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Old 04-12-2016, 10:58 AM
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Quote:
Originally Posted by BillGrissom View Post
For those that don't know, the only thing that retracts caliper pistons is a slight rotation of the square O-ring. There is no spring return. It works amazingly well, but only if the piston is free to slide. Some of the earliest front calipers on 60's Mustangs and Darts would get stuck from rust, which is how after-market Stainless Steel Brake Company got their start.
I also suspected that any small amount of run out of the brake rotor. Just might help the retraction of the piston or pistons a little as well.

As calipers age. The pistons ability to slide easy is perhaps deteriorating as well. It is odd that the slight play in the bearings is also a factor I never considered this as well. Yet agree.

I have noticed a few times people doing brakes and not cleaning and lubricating the caliper slide systems. There are specific lubricants but others can be used with caution. This should always be done as well. It usually only takes a few minutes.
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Old 04-12-2016, 03:06 PM
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Like Barry, I don't put much faith that the "rotating square O-ring" retracts the caliper piston except in new calipers. Certainly, slight play in the wheel bearings and even rotor waviness help push it back.

Most cars have "sliding calipers", like my 300D's. Note that the pins do not take the force of braking. That acts upon the "caliper bracket" which is integral with the spindle (knuckle) in many cars. The caliper pins just keep it aligned radially. In my 1985 300D, I hear a slight click when I first apply the brakes, which is probably excessive gap between caliper and bracket. Some pads come with shims for that, though I don't recall any last time I replaced 300D pads.

Many people consider "fixed calipers" better, and they are common in racing. The caliper body is bolted rigidly to the spindle. There are pistons on both sides. Early ones, like on 60's Mustang's had an external tube route fluid to the outside pistons. Of course, in tuner world much is bling, with flashy calipers w/ 6 pistons.
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