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Rear brakes locked up!


LuckyLobo

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I try very hard to look through the forums first, before wasting any time. I can't find the answer to my problem. Today, out of the blue, I drove my 1989 BII XLT three miles down the road. At times, I have noticed my rear brakes sticking a bit. I try to not use my emergency brake, because it old and it does have a tendency to stick. The cables are old. I was mostly fine, until I stopped to get my mail, 1/4 down the road at my box. I started up and backed out and noticed a lot of pressure, like the back brakes were on. I drove forward for a bit and had to pull over to make sure I didn't the e brake pushed down a bit. it was not. I turned off the engine again to chat with a friend. I started back up to drive home and could not move. I tried reverse and forward, to see if they would break loose. I had to put it in 4x4 low and in first gear just to get it to the end of the driveway. That was it! I got underneath to check the ebrake cable. it was limp. I took a hammer and smacked the drums. Both back wheels are locked up! I tried again, in 4x4 low to rock back and forth with no luck. Very strange that this would happen at the snap of a finger. Could this be an ABS failure of some sort? What can I check? I did find an electrical connection that was dangling down behind the ebrake pedal, but maybe it's always been disconnected. Thought? Things to check? I'm dead in the water and live in the middle of nowhere with no mechanics, at all.

Tom
 


3rd Petal

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I'd start by trying to get the drums off to see what it looks like in there. If the brake shoes are locked up against the drum, that will make it very difficult to get the drums off. You can crack the bleeder valve loose if you cant get the drum off, and that should relieve the pressure if it is somehow holding hydraulic pressure in the brake system.
It is also possible that something broke or came loose and is now wedged inside the drum.
One more possibility is that it isn't in the brakes, it could be something in the 3rd member. So if you get the drums off and still cant turn the rear end, you've got a problem inside the axle
 

ab_slack

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Wheel bearings could be an issue too.

I am assuming you lifted each wheel (one at time or both at the same time) and had it in neutral and verified neither would turn.

It does seem very odd that both would be locked at the same time.

Parking brakes usually don't hold that hard, they would have had to been dragging before you stopped and maybe with warmth have froze?

Sounds like hydraulic pressure wasn't releasing for the rear to hold that hard.

I immediately would suspect a collapsed brake line. I had that problem with my front brakes but I don't think that happens with metal break lines. What I mean by collapsed is with rubber break lines there are multiple layers and over time the inner layer can start coming apart. Externally they look okay but rubber than has come loose can act like a flapper valve preventing pressure from getting to your brakes, or in a case like this, act like a check valve allowing fluid to go to the brakes but not release.

The problem is that I don't think the rear brakes have a rubber line. At least not at the wheels. If there is a rubber line someplace I would be suspicious of that.

You can opening the bleed valve and see if there is pressure built up there.

It is also possible something in the RABS hardware not letting pressure release or the master cylinder.

It seems unlikely that the hydraulic cylinders in each wheel went bad at the same time.

Getting back to the parking brakes, I rebuilt my rear brakes and replaced parking brake cables last summer. My cables were loose under the car but corrosion in the last stretch of the cables going into the drums had frozen. Consequently they were stuck in the engaged position and because of that the return springs on the brake shoes couldn't pull them back and they were dragging. Without those springs pulling back the cables, the cables underneath were VERY lose. I won't say they should never be loose but the springs in the drums should pull the cable back so if everything seems really loose it may actually be a sign that your parking brake is stuck.

Getting the drums off can be a pain. First thing first, turn the adjustment screws to release the pressure from the drum. If I recall correctly it should help release the pressure be the source from the hydraulic system or parking brake.

Even without brakes jammed the adjustments should be loosened just cause drum wear will tend to make a small lip so extra clearance is needed to slip the drum off.

Getting the adjuster screws in the drums to turn doesn't require a special tool. I did with a screwdriver. The pain is that you need to push against the self adjuster plate otherwise you can only tighten them and not adjust them looser. I used one screwdriver to hold that plate off the adjustment screw and used the second to push against the teeth on the adjuster to turn it. It is somewhat tedious but is much better than trying to get the drums off with pads pressing against the drum.


Did they release after sitting awhile? I am trying to recall if there are any rubber lines in the rear break path. If there are
 

jayterrence

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Brakes

I have a 1990 XLT and i am having the same problem with the rear wheels locking up, only after a hard application, the rears will stay locked on until the springs push the fluid back and they finally release. i happened a couple times in the past 2 years and i began my search as to the cause. Most common reported cause is the ABS modulator, or RABS module located on the drivers frame rail just above the fuel filter, they get plugged and won't release, this model was used on many vehicles and they have had reports of them doing this for years but even though it was investigated, they were never recalled and considered safe. I am about to replace every part on the the rear, but not before i order a new RABS , $114.00 plus core charge of $57.00 online USA, and here in Canada they wanted $700.00, what a rip!!!!
 

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