Brake System Questions

[JimLev]

I merged your 2 posts, same topic, keeps confusion about the same questions being asked in 2 posts.

[traksion]

I would suggest the e-brake set up cable between the lever in the cabin and the rear shoes.
Did you check it, replace it, and made sure it is connected and screwed in right ? Maybe you need to replace ; it is a PITA to remove and install.

When I had a similar problem. that was the culprit. I'd advise you NOT to drive the car until you fix it.
It can be literally dangerous if it locks on you while speeding on a highway.

A temporary solution would be to remove it or cut it off with the rear shoes fully open and released. The car will drive fine and safe, but then, you will have no emergency manual brake if needed.

It's not an e-brake issue i've completely removed the e-brake assembly from both sides of the rear to rule it out.

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I merged your 2 posts, same topic, keeps confusion about the same questions being asked in 2 posts.

Ok no problem

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I would think you have 2 inter-acting issues:
-- the bad wheel speed sensor that effectively messes up or disables the ABS.
-- air in the ABS lines and/or brake lines that has not been properly bled out.

So, I would proceed as follows:
-- -Get and install the right oem speed sensor.
-- Install all the other hardware: ABS, lines, master-cylinder, calipers, pads, rotors....etc..and close the bleed screws.
-- Bleed the air out of the ABS lines : use INPA and activate all the valves on all wheels
-- Bleed the air out of the brake lines, and refill master cylinder. No INPA here. You can use a power bleeder if you want. Although the manual one-man-method works just fine.
-- Run Tool32, test-lenwinkel job to reset all the error codes and trifecta lights.
--Test. and tell us how it works.

Thanks Chedley, Waiting for my sensor should be here in about 10 days and then i'll report back.

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I just had an issue with one front brakes, sort of the opposite as it was clamping on the rotor slower than the others. It turned out to be a partially blocked ABS module valve/solenoid. May be worth also checking your ABS if you've already exhausted all other alternatives.

Like replacing the unit or some other tests? I'm not sure how to check it out aside from activating the solenoids through INPA.

[crdiscoverer]

Like replacing the unit or some other tests? I'm not sure how to check it out aside from activating the solenoids through INPA.

You have two options depending on how far you want to go: you can remove the plastic cover and with a strong magnet pull each solenoid. You should hear them "click". If one of them doesn't make any sound, it's stuck. Depending on whether it's an input or output valve, it could cause your caliper to lock up, not releasing brake fluid pressure (if that can't happen, someone correct me, please). You can lightly tap on the stuck solenoid to try to loosen it up.

The other option would be taking the whole module off the car and bench test it with compressed air, like so: https://www.youtube.com/watch?v=Dh82Ohnl9IE. The one bubbling is partially stuck.

[rdl]

It seems to me that the ASC/ABS control block is a strong suspect as mentioned above. The attached PDF may help to understand. It's a DSC document, but early in the document is wording that suggests the difference between ASC and DSC is software and the hydraulic circuits and various valves are at least similar.

Look at the diagram on page 5 of DSC part 2[1].pdf (labeled as page 19 of the complete document) Since you've described that cracking the bleeder on one caliper releases the "seized" brakes on both sides, one suspects problems with the preload valve, changeover valve or check valve in the half of the block for rear brakes. Not the inlet and outlet valves for the individual calipers.

It could be in the forward half of the master cylinder (dedicated to the rear brakes), but they usually leak and won't apply braking rather than seize and refuse to relieve the pressure.

I'd try removing the electronic module so that there is no chance that the solenoids in the electronic module is holding one or both valves in the wrong position. It will be safe to drive the car with the electronic module removed as the default position of all valve must allow full, proper brake function as a matter of safety. Imagine if the ASC or DSC lost power and the car's braking were impaired! If you do drive on the road be careful since there will be no ABS or stability function - just plain old style brakes. I've done it and lived to tell, although I've DSC, not ASC. Wrap the exposed hydraulic block in plastic to protect it from road dirt.

Then apply the brakes and check if the symptoms are still present. If OK the problem is in the electronic control module.

[traksion]

@rdl, thank you for the details and attachment I will try this today and report back.

[traksion]

Hi RDL,

I installed the new wheel speed sensor in the front right today and unplugged the ABS module but it still seems locked up. I don't want to force my clutch too much as I'll mess it up but I think at this point i've exhausted my knowledge and toolsets i'm going to throw in the towel and have it towed to a specialist unless there's any other ideas you might have or anyone else for that matter.

Thanks everyone for your help!

[JimLev]

Have you tried to loosen the bleeder on that wheel to see if it will allow the piston to retract and allow the wheel to spin freely?

[traksion]

Have you tried to loosen the bleeder on that wheel to see if it will allow the piston to retract and allow the wheel to spin freely?

It releases it slightly but not all the way.

[JimLev]

If the bleeder is open and the wheel doesn’t spin freely the piston or the slider pins that hold the caliper should be looked at.

[traksion]

Hey Guys,

I got word back from the shop i towed the car too to get diagnosed. They said the ABS pump is rusted out and is the cause of my problem. The part # is 34516756341. They quoted me $1100 to get it fixed.
Wanted to know your thoughts.

[JimLev]

See post 59. If you have the bleeder open there should be no fluid pressure holding the pads to the rotors.
That needs to be fixed.
Did you see the rusted out ABS pump?

[StephenVA]

water in brake system...what could go wrong? See brake fluid change recommendations (every two years). There are articles all over the auto repair trade journals on ABS units failing on Euro models. All have the same issue NO MAINTENANCE by owner(s).

[traksion]

Hi Jim, from what I recall after releasing pressure from the bleeder valve it did free up just felt tighter when compared to rotating the front wheels. The shop said everything in the back looks fine they only mentioned about the rusted out block behind the ABS unit that I did get serviced when I purchased the car. Since I purchased it I had not serviced the brakes as they still had life so i'm not sure about the previous owners but from the sound of it, it was neglected. I did not see the rusted out ABS pump. Looking around online they are quite pricey, much cheaper on ebay but that's risky.

[traksion]

I went to the shop and saw the valves when the computer unit is removed were indeed rusty, i just bit the bullet gona have them swap it out and hopefully that's the end of this issue.
Thanks for all the help folks.

[traksion]

For anything who might be running into the same issue than me. My problem ended up being the ABS pump behind the computer on under the hood. I had sent my computer unit out to a service for repair due to the heat shield issue.
It's possible when I reinstalled it I failed to reinstall the gasket although i find it highly unlikely it's possible and when pressure washing the engine bay water might have gotten into the seams and caused the pump unit to rust. You can easily remove the computer by unscrewing the bolts and checking if the valves look rusted that could be your problem as well. Shop replaced and coded the new unit and my brake problem is now gone.

[StephenVA]

Congrats!