ABS Issue - rear left wheel skidding under heavy braking

[jakubw28]

Hi everyone,

I recently bought a beautiful Monaco Blue E85, and while I absolutely love it, I've encountered a pretty alarming issue. Whenever I brake hard enough to activate the ABS, the rear left wheel completely locks up, no matter the speed, and stays locked until the car comes to a complete stop.

The first time it happened was terrifying—I was doing 50 mph on the motorway and had to slam on the brakes. The pedal went spongy, and that wheel just locked up. Otherwise, the car drives perfectly, and the brakes work fine during normal use. This issue only pops up during emergency braking.

I've had the car diagnosed multiple times, but no fault codes show up, and everything else seems to be in working order. To investigate further, my mechanic deactivated the ABS and tried to replicate the issue, but the wheel didn’t lock up this time, confirming that it’s definitely ABS-related. He suggested that the problem could be a seized valve in the ABS hydraulic module, possibly due to lack of use over time.

Now, I’m stuck deciding between two options: Should I buy a new ABS hydraulic module, or would it be better to have my current one repaired by a specialist? I’m particularly concerned about potential coding issues if I go the replacement route. Since no fault codes are showing up, it seems unlikely to be an electronic problem.

Any advice or experiences would be greatly appreciated!

Thanks in advance!

 

[damocell]

What year/engine etc is your Z4 and do you know the part numbers on your ABS pump?

I've had a spongy pedal recently and didn't want it code in a new ABS module, especially as for mine they are so expensive. I found one from a E9x 3 series and swapped the electronics over. Plugged it in and away I went. Solved my problem as I could see the seals in my old unit weren't in the best of shape and was also the cheapest option. Pic below of the ABS unit taken apart

Untitled by Damien Bower, on Flickr

 

[B21]

Hi everyone,

I recently bought a beautiful Monaco Blue E85, and while I absolutely love it, I've encountered a pretty alarming issue. Whenever I brake hard enough to activate the ABS, the rear left wheel completely locks up, no matter the speed, and stays locked until the car comes to a complete stop.

The first time it happened was terrifying—I was doing 50 mph on the motorway and had to slam on the brakes. The pedal went spongy, and that wheel just locked up. Otherwise, the car drives perfectly, and the brakes work fine during normal use. This issue only pops up during emergency braking.

I've had the car diagnosed multiple times, but no fault codes show up, and everything else seems to be in working order. To investigate further, my mechanic deactivated the ABS and tried to replicate the issue, but the wheel didn’t lock up this time, confirming that it’s definitely ABS-related. He suggested that the problem could be a seized valve in the ABS hydraulic module, possibly due to lack of use over time.

Now, I’m stuck deciding between two options: Should I buy a new ABS hydraulic module, or would it be better to have my current one repaired by a specialist? I’m particularly concerned about potential coding issues if I go the replacement route. Since no fault codes are showing up, it seems unlikely to be an electronic problem.

Any advice or experiences would be greatly appreciated!

Thanks in advance!

IMHO best to send it to a DSC specialist for analysis and repair,..

 

[jakubw28]

My Z4 is a 2.5si 2007, how much do these ABS modules usually go for? When i checked on Ebay they were about £250 (electronic + hydraulic) module together

 

[damocell]

My Z4 is a 2.5si 2007, how much do these ABS modules usually go for? When i checked on Ebay they were about £250 (electronic + hydraulic) module together

That's how much it was for mine. I wasn't prepared to spend so much and risk it not solving my issue. The part numbers are on the ABS unit, it might be worth checking which one you have as it appears they do fail.

I followed a thread on here about splitting the unit which was very easy. The replacement E90 ABS unit was only £70 from a local breakers to me and as it uses your current electronics, it doesn't need coding.

The thread can be found here: https://z4-forum.com/forum/viewtopic.php?t=135378&start=15

 

[enuff_zed]

Has the car had a brake fluid refresh lately? If so, did they carry out the full bleed procedure, including activating the ABS pump?

 

[_Paclunch]

Hi everyone,

I recently bought a beautiful Monaco Blue E85, and while I absolutely love it, I've encountered a pretty alarming issue. Whenever I brake hard enough to activate the ABS, the rear left wheel completely locks up, no matter the speed, and stays locked until the car comes to a complete stop.

The first time it happened was terrifying—I was doing 50 mph on the motorway and had to slam on the brakes. The pedal went spongy, and that wheel just locked up. Otherwise, the car drives perfectly, and the brakes work fine during normal use. This issue only pops up during emergency braking.

I've had the car diagnosed multiple times, but no fault codes show up, and everything else seems to be in working order. To investigate further, my mechanic deactivated the ABS and tried to replicate the issue, but the wheel didn’t lock up this time, confirming that it’s definitely ABS-related. He suggested that the problem could be a seized valve in the ABS hydraulic module, possibly due to lack of use over time.

Now, I’m stuck deciding between two options: Should I buy a new ABS hydraulic module, or would it be better to have my current one repaired by a specialist? I’m particularly concerned about potential coding issues if I go the replacement route. Since no fault codes are showing up, it seems unlikely to be an electronic problem.

Any advice or experiences would be greatly appreciated!

Thanks in advance!

Had this same issue. Rear left wheel was locking under ABS events, all three other wheels would lose brake pressure and I would slide to a stop, even when lifting my foot completely from the brake pedal.

Issue was caused by the hardlines being plumed in wrong when the brake system was overhauled by the previous owner.

I posted my answer in a similar thread. I have pictures of the ABS module and an explanation.

 

[bigwinn]

Had this same issue. Rear left wheel was locking under ABS events, all three other wheels would lose brake pressure and I would slide to a stop, even when lifting my foot completely from the brake pedal.

Issue was caused by the hardlines being plumed in wrong when the brake system was overhauled by the previous owner.

I posted my answer in a similar thread. I have pictures of the ABS module and an explanation.

I endorse this- had a car with similar issues where the lines were refitted into the wrong ports on the ABS unit