All brakes locked up

[Goatman]

Was driving down the road and driver front started to grab every time I touched the brake pedal. Within a half mile it was trying to throw me into oncoming traffic. Stopped at a garage to have it looked at. By the time they got it to the lift all four corners were locked up so hard the clutch was smoking just to move the Jeep. After I got a ride home they called with a $1500 repair bill. Any ideas what could have caused this? Had all four corners brake pads installed a few weeks ago. What the ??

 

[Steel City 06]

When was the last time the brake system was flushed (not just bled)?
@mrblaine specifically warns anyone installing his kits three separate times in the instructions to flush the brake system before pushing the pistons back into the calipers. I suspect that could be a cause. However that wouldn't normally lock up all wheels.
Other causes could be a malfunctioning brake booster, proportioning valve, or a trashed master cylinder. Do the brakes remain locked with the engine off?
$1500 sounds steep, although with labor I could see a brake system overhaul getting up there. The heat from the seized calipers may have caused damage to other brake components.

Are there any brake system modifications you know about on this Jeep? Or switches/valves, etc., that you're not sure what they do?

 

[Boinked]

Was driving down the road and driver front started to grab every time I touched the brake pedal. Within a half mile it was trying to throw me into oncoming traffic. Stopped at a garage to have it looked at. By the time they got it to the lift all four corners were locked up so hard the clutch was smoking just to move the Jeep. After I got a ride home they called with a $1500 repair bill. Any ideas what could have caused this? Had all four corners brake pads installed a few weeks ago. What the ??

First and foremost. Get a second opinion.

2nd. . . if you paid someone to replace the brakes a couple weeks ago. Call them and tell them what happened. Hopefully they are honest and will look at it and fix it if they did something wrong.

3rd do NOT DRIVE IT.

 

[mrblaine]

I'll bet good money the booster vacuum valve is malfunctioning and is slightly applying the pushrod into the master. The result of that happening is the replenishment ports get covered. When that happens the fluid can go back into the reservoir when the brakes heat up and expand the fluid so instead they start applying the brakes which heats them up, which expands the fluid more, so on and so forth until all 4 corners lock up hard.

1- let it cool, jack it up and see if the wheels are freed up. If they are, it isn't the calipers and wheel cylinders most likely.
2- if they are still locked up, open a bleed screw and see if that frees things up so the wheel can be turned. If not, that points to the caliper being the problem. (unlikely)
3- if they aren't locked when cool, then pull a caliper and with the engine running, see if the piston can be pushed in. If it can't, that points to the master/booster if the brake light on the dash is off. If it is illuminated with the parking brake off, that points to the combo valve but I'm not sure how that could lock up all four.

What does the estimate involve? Sounds like a shotgun diagnosis so far.

 

[mrblaine]

3rd do NOT DRIVE IT.

How far will it go with all 4 locked up and the clutch smoking to just move it around?

 

[Boinked]

How far will it go with all 4 locked up and the clutch smoking to just move it around?

In today's world it needs to be said.

 

[Goatman]

All 4 locked up going perhaps 100 feet in to the shop. All 4 locked up while on the lift 20 minutes after it was driven in. All rotors were discolored from overheating so they must have been dragging while I was thinking just 1 was locking up. Bought from a new car dealership a few weeks ago and was told they did all 4 with new pads. There were new pads all around. I checked by pulling all tires when I got it home. They were all new.

 

[Goatman]

$1500 is for new everything but lines. Complete flush, 4 new rotors, calipers, and m/c. At $115 per hour shop rate (actually on the low side around here) it adds up fast. Just lucky there was a shop right there. Otherwise I'd be in an accident or the morgue. Damn lucky.

 

[mrblaine]

$1500 is for new everything but lines. Complete flush, 4 new rotors, calipers, and m/c. At $115 per hour shop rate (actually on the low side around here) it adds up fast. Just lucky there was a shop right there. Otherwise I'd be in an accident or the morgue. Damn lucky.

It is possible the master is causing this directly but I'd be surprised if the booster isn't the problem. There isn't much in the master that can cause it to self apply since there are springs for both sections of the piston assembly that keep them pushed back to keep the replenishment ports open.

Are they replacing the combo valve and booster along with the master?

 

[Goatman]

Tires still can't turn when on the lift. Can't be the booster. Fruit was really dark. Almost black. I'm thinking it is probably crunchy too. I'm guessing the fluid has never been changed. Calipers too. Just throw on some cheap pads and call it good. Never understood this kind of thinking. Maybe my years as a helicopter crewchief, but I am extremely anal about service intervals and maintenance. Just real lucky that shop was there.