[nixkdn]

When accelerating the rear brakes (I believe) will lock up for just a split second and release. This only happens on very hot days and after driving for a while and is very random. I cannot make this happen by doing the same things over. This typically happens after reaching 55+ mph. I have taken the vehicle to several dealerships and have yet to find the problem. Has anyone experienced this or have any suggestions as to what to look for? Any ideas or thoughts would be greatly appreciated.

 

[ImperialCrown]

Welcome to Allpar. Are there any pad marks left on the rotors from when they seize? Is there any wheel dragging noted when the brakes are hot and the wheels are off the ground? I would want to start with maybe a fresh set of premium brand name brake pads and fresh rotors if this hasn't been done already. Axle seal leaks will soak the parking brake shoes with gear oil.
Also investigate other drivetrain components that may be in trouble. Has the differential cover been off for an internal inspection? Any bearing or gear noises?
Brakes don't really know if you are accelerating or not.

 

[KOG]

Traction control?

 

[nixkdn]

IC - I have had Chrysler and independent mechanics look at this and none of the issues you described were mentioned to me. The pads and rotors show no abnormal wear and are probably less than 10k miles new. Not positive if differential has ben inspected. Did not think of that. I will call and find out. But no bearing or gear noise. Even if pads were soaked, that wouldn't randomly apply brake on its own would it???

I agree brakes do not know acceleration but this is the only time it happens so just throwing all common denominators out there. Just as it only happens in extreme heat. This problem never happens during winter.

KOG - What do you mean by traction control?

 

[ImperialCrown]

Does this have a traction control option (works with the ABS system to lock the spinning wheel)? You would have a TRAC OFF button somewhere on the dash if you did. I don't think that it would be active at higher speeds.

 

[nixkdn]

it is the Laredo, so no it doesn't have traction control.

I am leaning toward this being a circuit board going bad. When heating up it is sending/not sending signal through ABS system causing the brakes to be applied. But only a wild theory on my part as the ABS system is intended to keep brakes from locking up.

 

[ImperialCrown]

Live data on a scan tool while driving and being able to get it to act up may help diagnose this if it was electronic. Being very random makes diagnosis difficult.
If it left a fault code along with a freeze-frame, it might help to put together what is happening here. There are data recorders for engine controllers, but maybe not for passenger car ABS control modules.
Unplugging the module temporarily for diagnostic purposes is a possibility, but is dangerous if you needed an ABS stop and didn't have it available. Therefore I can't really recommend that. It's up to you.
ABS won't apply the brakes. That is why I'm leaning more towards an intermittent mechanical problem, but lets keep an open mind as to the cause for now.
http://mycollisionconnection.com/issues/1/abs_ecu.html

 

[nixkdn]

No fault code is being sent. I will ask my mechanic about the possibility of using a scan tool while driving. But being so random is the problem. It's been over 3 weeks since it has happened and all the conditions I mentioned earlier have been present. Texas summers makes it pretty simple to find hot conditions.

You mentioned the differential earlier. What was your thoughts there?

My only other thought would be a problem in the rear end if not electronic. But this has spanned over a couple of years now and I would think I would be experiencing other issues if it was in the rear end.

I really do appreciate any and all comments received. I'm absolutely clueless and it seems I have several mechanics stumped as well. Love a good mystery, just not so much in my car.

 

[kev2]

your issue is a feeling of not releasing - hanging up caliper? - if so -
I have seen the flex brake hoses fail - an internal issue, they can act as a check valve .
Often happens when the component is allowed to hang during repair or twisting during install, ie pad or rotor replacement..

 

[nixkdn]

kev2 - Are you saying the hoses could randomly fail upon acceleration? I can see where the hoses possibly could collapse, acting as a check valve, and not releasing. But the brakes are definitely releasing upon acceleration. Please explain further if I misunderstood your question.

 

[kev2]

Did I restate your issue correctly- I am not sure....

The hoses failure is INTERNAL ... the deterioration not visable BUT with the varing brake pressure an intermitant.
Try this - remove affected wheel - apply brakes heavly... then release - open the bleeder if there is a restriction fluid will express under pressure....

Another interpatation* of your issue - MAYBE a diffferential problem.... do you have AWD or locking/posi rear?

*sorry every time I read OP I interprete differently... getting old I guess

 

[nixkdn]

KEV2 - I'm pretty sure not a hose issue. If not mistaken, that would cause the brakes to not release and that is not the case. It is not AWD or locking/posi rear.

Please tell me your thoughts on the differential?

I'm still leaning towards this being a circuit board issue just because this only happens on extremely hot days and the jeep has been driven for at least 30 or 40 minutes. Both the outside temp and car temp combining to either expand or contract leads on one of the circuit boards controlling the brakes. Wild theory I know but I'm stumped and grasping for any ideas.

As for getting old, you'll have to get in line behind me.