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Rear Calipers STUCK Clamped; Won't Release!


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13 replies to this topic

#1 MorganM

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Posted 15 September 2004 - 09:03 PM

So I finally get the wheels on and go for a test drive. Completed a rear disc conversion last week. Ran some hardline in the rear. Bleed the system lastnight and pedal is solid. Fire her up tonight to move it into the street for my windshiled install tomarrow and to test my new rear discs.

While putting on my wheels I can feel the calipers are clamped down. I figure no big deal they will bust loose when I get moving. Fire her up and back out... still grabing hard. Went down a block and came back. Could hear them the whole way and feel that they were clamped down hard.

When I had the calipers off I pushed the piston on the brake cylinder in so the pads would slip over the rotor. Seemed VERY easy to push them open. I lubed up all the seals right there around the piston and the whole caliper. Repacked every boot with new grease.

Any ideas on how to bust them loose or to get them functioning properly? I'm at a loss and need some ideas to atleast look into.

Thanks!

#2 edrach

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Posted 15 September 2004 - 09:15 PM

You are so lucky! The first one ever to have trouble with the rear disk conversion. Only thing I can think of is there's air in the lines that's expanding and causing the rears to lock up. What really puzzles me is why the fronts aren't giving you the same problem. I'd consider opening the bleeder on each rear separately when they are locked and see what comes out. You might have some particles in the brake fluid causing it to act like a checkvalve and keeping the pressure up. Bleed enough fluid out and you might fix the problem. Are both rears grabbing or just one?

#3 PoorManzImpreza

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Posted 15 September 2004 - 09:41 PM

discs really corroded? new brake lines installed correctly? new brake fuid in the entire system? bleed the entire system?

dunno man sounds pretty weird..I've had dragging in the front cause I rebuilt the calipers but neglected to readjust the handbrake when I put em back on..duh..lol but on the back? dunno man..

#4 MorganM

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Posted 15 September 2004 - 09:43 PM

One seems to be grabing harder than the other since one would I could barely spin with my hand and the other I could not spin at all.

I thought air in the lines meant it would be extra squishy... less pressure.

#5 edrach

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Posted 16 September 2004 - 12:52 AM

You're right about air in the lines...my fault. How about water? Brakes get hot, water turns to steam, and now you have lots of pressure. Bleed and replace the fluid; use new fluid which hasn't had time to absorb water. I still don't know why it shouldn't affect the fronts at the same time.

One seems to be grabing harder than the other since one would I could barely spin with my hand and the other I could not spin at all.

I thought air in the lines meant it would be extra squishy... less pressure.



#6 TomRhere

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Posted 16 September 2004 - 03:06 AM

Would suggest taking a look at the pads again, just to make sure they a sitting in the caliper where they are suppose to be. Could have them in wrong.

#7 MorganM

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Posted 16 September 2004 - 09:31 AM

Would suggest taking a look at the pads again, just to make sure they a sitting in the caliper where they are suppose to be. Could have them in wrong.


Hmm possibly. I've never done rear pads and these were almost new. Maybe I didnt slip them back fuarther and make more clearance for the rotor?

As for water and steam; all this happend before moving. No heat built up to create steam :( I put on the calipers, bled them quickly (4 pumps at each point) and they were just locked up in the rear. I certainly agree with more bleeding :)

Ugh... prolly time to pull them off and find out :rolleyes:

#8 stephenw22

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Posted 16 September 2004 - 10:28 AM

Last time I did rear brakes on my '85, the passenger-side rear caliper acted the same way. After a long process of elimination, I eventually decided that there was probably something in the caliper that was catching or sticking when it was pushed in that far. My guess is that moisture in the fluid had rusted the caliper internals a bit.

Solution - I took a grinding wheel to my new brake pads and took off about 1/3 of the pad material. I put the 'pre-worn' pads on the car, and the problem went away. A new caliper would have been the ideal solution, but brake pads are a lot cheaper than new calipers.

#9 MorganM

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Posted 16 September 2004 - 10:37 AM

Shadow: No rear porportioning valve. All the lines back there to it and the valve itself were so teribly rusted they were not salvagable when the lines finally started leaking :( Would a stuck Hill Holder calmp down just the rears and not the fronts? I thought it worked cross directionaly... so only one rear would clamp; right?

stephenw22: Certainly a possibility with the rusted internals. The calipers (and everything else with teh swap) was salvaged off a junkyard GL10 turbo wagon. Not a whole lot of rust on her but sitting there for so long with any water in the lines I'm sure isnt good.

Good idea with the pads ;) The ones on there are practicly new; and very beefy. I could try shaving them down some. I'll prolly bleed it a bunch more first with fresh fluid. See if something gets dislodged in the rear caliper cylinders. Iff that dont work I'll pull them off and look again. All else Ill try the pads.

#10 MorganM

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Posted 16 September 2004 - 01:14 PM

Called all my local Subaru stealerships and talked to service techs. Most seem baffled or unwilling to talk about it. One said I have to use the master cylinder off of the car with rear discs. This seemed fishy to me so I called up a parts department. Asked if there was any difference in master cylinders on an '88 GL with rear drums vs rear discs. He said the only difference is if you had a hill holder or not; other than that they were the same.

I have 2 more techs to call that were out of office for a few hours. I spose I'll see what they say also. Wish I was at home worknig on them intead of just sitting here wondering :(

#11 Qman

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Posted 16 September 2004 - 07:27 PM

I have seen bad rubber hoses allow fluid flow in one direction and not the other. It could be a rust situation I suppose. That is easy to find out though. All you have to do is remove the caliper and remove the piston. Clean the surfaces with a very fine emery cloth and reassemble with new o-rings and dust boots. Basically a rebuild of the caliper. Try opening the bleeder valve and see if the pressure releases itself. If you can turn the rotor with the valve open then it's a problem with the rubber lines or the caliper itself.


Ken

#12 MorganM

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Posted 16 September 2004 - 09:45 PM

Thanks for all the suggestions guys. I had some time tonight so me and my son jacked it up, took off the wheels and started looking for the problem. Found it pretty quickly. :)

Typical; it was just something stupid I had forgot to do.... washers are key :rolleyes:

Now onto my custom bumpers and I'm ready to go to the Castana Offroad Event !_!

#13 edrach

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Posted 16 September 2004 - 10:53 PM

Glad it's fixed. It just goes to show ya, stop looking for the difficult things and stick with the simple stuff.

#14 archemitis

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Posted 17 September 2004 - 09:36 AM

har! ye be smokin too much crack matey!




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