Author Topic: stuck caliper  (Read 249 times)

raueda1

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stuck caliper
« on: 30 June 2019, 08:22 AM »
 If it's not one thing it's another.  When I arrived at a friend's about 5 miles away smoke was pouring up f th one one wheelwell.  Looks like the caliper stuck.  Wheel and tire were very hot.  No brake problems in the past.

How common is this and are there typical known causes?  I'm ready to rebuild the calipers assuming kits are out there (haven't looked yet but I'm sure there are).  This is also a good time to replace brake hoses.  I'll have car on a lift later this afternoon for better diagnosis.  Still, in the meantime if anybody has comments They'd be appreciated.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

kepa75

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Re: stuck caliper
« Reply #1 on: 30 June 2019, 08:26 AM »
Hello,

This happened to me lately on a back wheel.

Ciao,

Peter

raueda1

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Re: stuck caliper
« Reply #2 on: 30 June 2019, 09:01 AM »
After sitting overnight the wheel moves freely so car is more or less mobile. 
General brake question:  the pads are pretty new.  If so, and if rotor looks ok, can old pads be put back (in same positions I assume)?
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Squiggle Dog

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Re: stuck caliper
« Reply #3 on: 30 June 2019, 01:06 PM »
One likely cause could be old brake hoses--the rubber inside breaks down and they clog, so they work like a check valve-- you can apply the brakes, but then the fluid can't return, so the pressure stays applied to the disc. I find this is the most common cause of dragging brakes.

Another cause could be brake pads and rotors that are worn down too far. If this is the case, then simply replacing the brake pads might make things right again. But, I see that your pads are new, so this won't apply, unless your rotors are very worn and have a lip. If the pads are glazed from overheating, then you can try sanding the glazed surface off, but otherwise they should be replaced.
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revilla

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Re: stuck caliper
« Reply #4 on: 30 June 2019, 01:26 PM »
Not a rare occurrence.
Last summer we did the brakes of a friend’s 450. Both rear brakes were dragging, one of them quite severely! In that case the root cause was corroded pistons and calipers chambers (with even pinholes of corrosion in the pistons lateral surface). Also the rubber seals were quite hard. We changed the pistons and seals. He brought a MB light blue tube caliper grease that a local MB dealership manager lent him. Sorry I don’t have the PN. We didn’t do the calipers, we simply cleaned them internally. We didn’t change the hoses neither but I reckon we should have.
This summer (weather permitting, because we have quite hot temps around here these days) I have to do mines. I think you should put new pads by principal, especially considering they aren’t expensive.
Robert
W116 1977 280SEL & 1979 280SE

daantjie

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Re: stuck caliper
« Reply #5 on: 30 June 2019, 01:59 PM »
I would do new pads, rotors and hoses in addition to the caliper fix  I find the Textar pads to have the best bite. I am amazed every time at the great brake feel these cars have when sorted. I replaced all brake components save for the booster when I got my 6.9 and it completely transformed the brake feel and performance.
Daniel
1977 450 SEL 6.9 - Astralsilber

Jed

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Re: stuck caliper
« Reply #6 on: 30 June 2019, 04:32 PM »
Yes! what he said! (Daniel)

I have never rebuilt calipers but if they look like my old ones just replace them, ideally in pairs.  If they were dragging for any significant amount of time the rotors likely heated up and may have warped.  So change pads, rotors, calipers.  If you have no record of hose replacement then change them too...hoses are cheap!

Easy work with a little patience.  If your fittings are corroded spray them with PB Blaster the night before and be sure to have good flare nut wrenches for the hoses and caliper metal lines. If they are stuck use heat and don't mess up the metal line fittings.

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w116john

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Re: stuck caliper
« Reply #7 on: 30 June 2019, 04:43 PM »
discs pads and hoses are reasonably priced and it is no harm changing them.

 front calipers are more expensive than the rear and that would be the last option

my fronts were getting sticky when hot and after replacing most brake components

it was the front hoses that caused my problem.

all the best

john




raueda1

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Re: stuck caliper
« Reply #8 on: 30 June 2019, 05:13 PM »
Thanks to all for the helpful comments.  This afternoon I got it all taken apart and diagnosed.  The caliper on the smokey wheel was leaking fluid from one of the pistons.  The pads were relatively new with ~7mm of meat left.  The rotors look good too - a very small wear lip on the outer edge but no serious scoring, no apparent warping and both sides look the same.  The caliper failure event clearly didn't take out the rotor with it.  The rotor did have some black junk where the fluid was leaking, causing me some brief alarm.  Brake cleaner took it right off though, so I assume it's just semi-burnt fluid.  The hoses weren't so nice. 

So, my plan:  new calipers and pads in front and new hoses all around.  Obviously I'll do a system flush. I just can't see much good  reason to replace rotors.  If anybody thinks this seems like a false economy please advise.  And so the adventure continues.....
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

TJ 450

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Re: stuck caliper
« Reply #9 on: 30 June 2019, 07:58 PM »
If the rotors check out OK, I would keep using them. When the time comes to replace them you could consider doing the wheel bearings at the same time, since you have to remove the hub anyway.

The caliper would have failed due to festering brake fluid at some point I would imagine.

Tim
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Squiggle Dog

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Re: stuck caliper
« Reply #10 on: 30 June 2019, 11:03 PM »
I would do new pads, rotors and hoses in addition to the caliper fix  I find the Textar pads to have the best bite. I am amazed every time at the great brake feel these cars have when sorted. I replaced all brake components save for the booster when I got my 6.9 and it completely transformed the brake feel and performance.

Textar pads have a good bite and I enjoyed the performance. However, I could not live with the excessive brake dust, so I went to Akebono ceramic pads. I also had the new genuine Mercedes rotors cryogenically treated so they will last longer, as ceramic pads can be harsh on rotors. I'm very happy with my decision as there is no brake dust to speak of. I took off my front hubcaps after a couple years and they are still sparkling clean on the backside.
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