[IsaacSA]

My question is simple my 13 X3 F25 seems to be having and issues of either the rear brakes locking up or the rear end locking up I can't tell which one it is. I was told that the brakes were locking up so I replaced all the braken lines with steel braided ones the problem continued. I then replaced the brake booster the problem continues. I was going to change the rear diff fluid but it was full and clean. I then changed the transfer case fluid which turned out it was low and real dirty but the problem continues. The rear brakes or diff lock up when the car is hot and driven for a while. I haven't replaced the brakes because I don't want to put new brakes on it and destroy the new brakes if the rear keeps locking up. I was told to replace the alternator but I don't see how that works with the brake system of rear end. The car has 125000 miles and I bought it used so can anyone put me I. The right direction so I'm not just throwing money at it.

[Hellshalfacre]

If the rear dif is actually "locking up" at speed you'll know it because the gears will exit the differential in dramatic fashion. At the very least you'll find a German Sparkle party in the fluid.

If you have suspected your brakes of being the issues to the point of replacing parts at random, you might want to at least take a good look at the brakes and calipers. That's kind of step one and doesn't cost anything.

I don't know what you mean by "destroying new brakes if the rear locks up." That doesn't really make sense, but in any case you should pull the rear wheels and check for excessive corrosion on the rotors, calipers and pads. If you have a way to check trans live data that could also point you in the right direction. Good luck to you.

[IsaacSA]

I appreciate the info. What I mean by damaging the new brakes I mean of they continue to lock up after I replaced them then I spent a lot money just to damage new parts. I have the brakes and yes the brakes are bad and need replacing I was told they were resurfaced and I did notice some banging wear on the passengers side rear axel . Idk if the calipers are locking . Also the transmission shift fine no issue with that especially since I've replaced the fluid in the transfer case.i hope it's something as easy as replacing brakes but for some reason my gut says no. I'll try replacing the brakes and update from there. Thank-you again for your input.

[carmoongia]

Just a thought there have been a couple of threads on here recently concerning a very similar issue to yours and the problem turned out to be the ABS block with floating debris in it, try doing a search, but definitely first port of call check for sticky pistons in the callipers, next time it happens drive a little and the very carefully feel the rear hubs if it’s the brakes the discs will be RED HOT you have been warned take care and good luck

[Hellshalfacre]

An advisor of mine who's been wrenching on German vehicles for 50 years professionally is of the opinion that many of the ABS related issues we're seeing in these cars is related to a simple and often overlooked procedure when removing/ reinstalling brake pads. He reports that the caliper bleed ports should ALWAYS be cracked PRIOR to compressing the pistons to avoid the back flow of debris, which collect at the lowest point in the system (the caliper,) back to the ABS pump. I have no data to support this, but I've been doing this for the last 10 years when replacing brake pads.
Excellent call on finding an offending caliper via heat. A cheap digital heat gun can really help in these situations. I've seen a difference of 80d F on a slightly sticking calipers.

[Opie55]

What do you mean by locking up? Your wheels stop turning or what? But you really need to figure out if your caliper pistons are freezing up at high temps. Go to harbor freight and get a cheap infrared thermometer. Drive around a bit using the brakes and shoot the beam at your discs after they "lock up". If it is the brakes they will be very hot - hotter than the front discs. Under normal conditions the fronts are hotter than the rears.

[IsaacSA]

I'll admit I'm not familiar with BMWs so it hard for me to determine the issue. I did disconnect the ABS module and it didn't make a difference. The rear wheels stop spinning and when I need to pull over the front wheel pull the car while the back wheels slide. I haven't inspected the car yet due to working weekdays I'll have to tear it down this weekend to get a better description on what the rear looks like. I am leaning towards the calipers sticking. I'm going to have to look into the ABS lines. I truly appreciate the replies I'll post updates as soon as I get the work done. Hopefully my thread will be helpful to other BMW owners.

[Dekero]

Your abs valve body has debris in it

Find a used one on eBay and swap your valve bodies over this way you don't have to code a new DSC you want to use your old one that's in your car now with the newer valve body do a full brake bleed and I recommend going ahead and bleeding out all the old fluid and refreshing it

I just had to do this on my daughter's X3 2011 model due to the front right brake locking up just solved it for less than 250 bucks

[HighlandPete]

Originally Posted by IsaacSA

I'll admit I'm not familiar with BMWs so it hard for me to determine the issue. I did disconnect the ABS module and it didn't make a difference. The rear wheels stop spinning and when I need to pull over the front wheel pull the car while the back wheels slide. I haven't inspected the car yet due to working weekdays I'll have to tear it down this weekend to get a better description on what the rear looks like. I am leaning towards the calipers sticking. I'm going to have to look into the ABS lines. I truly appreciate the replies I'll post updates as soon as I get the work done. Hopefully my thread will be helpful to other BMW owners.

Calipers sticking and wheels locking up are two totally different things.

I'm with ABS issues on this one.

[mayhewt11]

I have the exact same problem for months. I tried everything until I came across this article. Interestingly, this started happening almost immediately after getting rear pads and rotors done by a local repair shop. I replaced - all rotors and pads (Again), brake master cylinder, bled brakes once, didn't expect this at all!

The locking up has gotten significantly worse, it seems to happen most often when accelerating at higher speeds and BOOM, right when let my foot off the gas, the brakes engage HARD. Imagine this happening on the highway and when passengers are in the car. It's happening almost every time I drive now.

Will follow up with results from this repair.

[mayhewt11]

Originally Posted by Dekero

Your abs valve body has debris in it

Find a used one on eBay and swap your valve bodies over this way you don't have to code a new DSC you want to use your old one that's in your car now with the newer valve body do a full brake bleed and I recommend going ahead and bleeding out all the old fluid and refreshing it

I just had to do this on my daughter's X3 2011 model due to the front right brake locking up just solved it for less than 250 bucks

This is the correct fix for this issue, confirmed after 6 months of various repairs, finally!

[newworldman]

Originally Posted by IsaacSA

My question is simple my 13 X3 F25 seems to be having and issues of either the rear brakes locking up or the rear end locking up I can't tell which one it is. I was told that the brakes were locking up so I replaced all the braken lines with steel braided ones the problem continued. I then replaced the brake booster the problem continues. I was going to change the rear diff fluid but it was full and clean. I then changed the transfer case fluid which turned out it was low and real dirty but the problem continues. The rear brakes or diff lock up when the car is hot and driven for a while. I haven't replaced the brakes because I don't want to put new brakes on it and destroy the new brakes if the rear keeps locking up. I was told to replace the alternator but I don't see how that works with the brake system of rear end. The car has 125000 miles and I bought it used so can anyone put me I. The right direction so I'm not just throwing money at it.

Hi Isaac. I'm having the same problem as you. I'm also in San Antonio and have had Rhine West looking into it. They think it's a defective ABS module. Did you ever get a resolution/fix for your issue? My front brakes will engage hard at highway speeds and especially in wet weather (very dangerous). Looking forward to hearing if your problem was solved. I'm not looking forward to spending ~5k on a repair on a car that's not worth that much more.