All 4 brakes locked up???

Milehighbmw · #1 09-05-2018, 04:43 PM

02 x5

Like the title says I had all four brakes completely lock up as I was driving. By the time I got pulled over off the highway they were all 4 smoking.

I was having a problem with the brake light switch under the dash. It somehow gets pushed in occasionally to the point the pedal no longer makes contact and the brake lights stay on. I went home grabbed tools. Put it in neutral to see if it would roll as I was on a hill. Nope not at all. Got under the dash fixed the switch started it up brakes released drove it home.

Later that evening decided to try taking it on a short errand. By the time I got down the block they locked again. This time the brake light switch was still making contact. I got out and pulled the vacuum line and check valve from the brake booster. There was a loud release of pressure. Plugged it back in brakes went back to normal. Drove it on my errand and back home no problem.

I assume this isn't fixed and I'm stumped bad.

Codes from inpa were for pressure sensor, brakes overheating and brakelight switch. If I remember right. I'll post them when I get home later

Any ideas?

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Milehighbmw · #2 09-05-2018, 04:46 PM

When the brakes are locked up the pedal is super hard and will barely move when trying to press it. I plan to replace the check valve since it's only $6. No idea if that might help but I won't loose much either way.

Any other ideas will be greatly appreciated. There's usually 50 posts on any of the problems I've had with my BMW's this one not so much....

andrewwynn · #3 09-05-2018, 05:57 PM

Somebody else had the exact same problem recently do some more searching and see if he found a resolution

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Russianblue · #4 09-05-2018, 06:12 PM

I had this happen one time on my e28 and burned up my clutch getting home. The problem there was self-inflicted bc I had just replaced my brake booster and had adjusted the rod incorrectly. In your case, I'm not sure if the rod could have slipped and 'foot off the brake' actually means '10% of braking permanently applied'.

when 10% is applied (my rod adjuster thing was only off by a hair) and the brakes are cool, everything was fine. but 1000 feet down the road, the brakes got hot and expanded, then the effective braking was much greater. That's my THEORY anyway. That was right after I learned to work on my own car though and I didn't know what the hell i was doing.

Milehighbmw · #5 09-05-2018, 07:56 PM

I did a search with just (brakes) went b as ck about 15 pages. I searched brakes locking up. Nothing. Usually it's just one wheel caused by a bad caliper that's understandable. This the way it just comes and goes doesn't make any to me.

andrewwynn · #6 09-05-2018, 08:13 PM

Did you replace any hardware recently?

It seems like your abs precharge pump is running when it shouldn't. There is apparently some adjustment rod in that which if set wrong can apply the brakes automatically.

Milehighbmw · #7 09-05-2018, 11:22 PM

I have not replaced anything. I've only owned it a couple months. I'll research what the precharge pump does and how it works.

This is crappy I have new wheels and tires and I'm afrsid to drive it......

andrewwynn · #8 09-08-2018, 08:37 AM

https://youtu.be/G95-S9i40R8

Watch this video

Oltorf · #9 09-12-2018, 03:26 PM

I had this same problem. I replaced the brake booster and then took it in the to dealership to flush the brake fluid. When I got it back it started locking up the brakes. I could pull up on the brake pedal and the problem would go away.

I took it back to the dealership and they told me that because I put DOT 3 brake fluid in it, that caused the seals to swell which was the cause. That couldn't be it though because DOT 4 is the same as DOT 3 but with an extra additive. Also, the problem just kind of.... went away after a while.

I still have no idea what happened.

Milehighbmw · #10 09-12-2018, 03:40 PM

Glad to hear yours has been ok. I've drove mine on a few short trips now and it hasn't done it again. I'm nervous every time I drive it though just waiting for it to act up again. I wish someone would read this who's had the same problem and actually repaired it or knew the specific problem. I don't want to just start replacing things for no reason.

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