rear brakes dragging - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 7 Old 05-04-2011, 12:57 PM Thread Starter
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rear brakes dragging

Guys,

Had a great weekend at the track but was having a problems with my brakes dragging after coming off the track. You could not even push the car with two people. After about 40 minutes the brakes would release and I could push the car by myself.

I looked for a bent brake line but could not fined one. Also the back brakes were worse than the front.... at least I could jack up the car and turn the front tires alittle..... the back no way.

I don't have an e brake so thats not the problem, maybe the rear calipers are getting to hot and expanding against the rotor? Its aluminum, wilwood or I don't have the caliper centered on the disk but the pads are wearing evenly?


91 GT
349 A-4

Last edited by cgr7225; 05-06-2011 at 08:41 PM. Reason: spelling
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post #2 of 7 Old 05-04-2011, 04:08 PM
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Rotor "coning", going from a 2-D flat plane, into a 3-D cone, and thus dragging?
Just guessing?


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post #3 of 7 Old 05-04-2011, 11:04 PM Thread Starter
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Talking

Straight edged the disk on both sides and no coning as far the rest of your statement my friend.......... I don't know if you're blowing smoke having fun with me or that ending 2D/3D thing means anything but I did get a good laugh. Thanks!!

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post #4 of 7 Old 05-05-2011, 12:13 AM
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The pushrod coming out of the power brake booster is probably adjusted slightly too far forward. This keeps the m/c piston from being able to retract all of the way. The end result is the brakes stay locked. It almost always happens when the brakes are hot.

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post #5 of 7 Old 05-05-2011, 12:18 AM
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I'm also guessing but I think I would want to convince myself that it's a mechanical vs. a hydraulic problem. How does the pedal feel with the engine running (so there's vacuum) and the brakes locked up? The brake fluid cap, fluid level and reservoir look normal?

Maybe next I would pull a rear wheel and open the bleeder just to see if fluid comes squirting out under pressure with no brakes applied. If all that seems normal, while I had the rim off, I'd try pulling the pads just to see if either the inner, outer or both pads is just too tight against the rotor especially after you opened the bleeder and removed any hydraulic pressure.

Or, after I hit the post button, check what Jack recommends...

Last edited by SteveL1994; 05-05-2011 at 12:20 AM.
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post #6 of 7 Old 05-05-2011, 09:36 AM
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+1 on Jack's comment, the fact that they retract when cooled off tells you that they're probably not mechanically locking up or it wouldn't be so affected by heat (they'd stay locked up when cooled). Heating of the calipers may cause them to expand a little but the piston is what keeps the brakes applied, not the caliper body, so you're looking for a hydraulic issue. Since the fluid is allowed to return to the MC and the amount of return is adjustable there, the issue most likely stems there.

The only other thing I'd ask you is if there's any chance that there is any brake fluid contamination with a petroleum product (oil, power steering fluid, trans fluid, etc.) which could cause the rubber seals in the brake system to expand (moreso with heat). This is a bad situation and I've personally seen in it happen before (some bozo added power steering fluid to the MC by mistake).
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post #7 of 7 Old 05-06-2011, 08:54 PM Thread Starter
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Great idea Jack..... I should have commented on that in my opening thread. I took off the m\c from the booster when the brakes were locked just to see if that in fact was the case but the brakes remained the same, locked.

I do have a prop. valve next to a header and that may be the problem. I tried to insalute the valve with heat reflective material but maybe thats not enough.

I drove the car around the paddock trying to lock up the brakes again but the brakes refused to lock up. I mean they would stop and even lock up under brake application but would not lock up like they did before but of course I couldn't introduce the heat in the paddock like on the track. Must be something with the heat???

I'm the only one who works on this car so I'm sure no power stearing fluid found its way into the brakes. Thanks for the idea!!

I looked at the pads, M\C and fluid level, all look fine but I will have to check the bleed valve next time I can get the brakes hot enough to lock to see if the hyd fluid is under pressure just sitting there. Thanks guys. Keep the ideas coming.

91 GT
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Last edited by cgr7225; 05-06-2011 at 09:01 PM.
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