ABS Failure: Audi Allroad Troubleshooting

Hello.

I'm having the following problem:

Audi allroad 2.5 TDI V6, year 2002. 253,000 km.
The braking system overheated during the drive!
I noticed that the front left and rear right wheels were overheating. When you gently press the brake pedal (tapping it a few times), does the brake release? Otherwise, those two wheels lock up completely.

I have now replaced the brake booster and the master cylinder .
Unfortunately, without success! The problem persists.
Okay, I've now, when the wheels were locking up again, disconnected the individual lines at the ABS module (where the labels like "FL", "FR", etc. are located).

"There was a very high pressure in both the front and rear brake lines (a lot of fluid was spraying out). There was no pressure coming out of the other two connections. After that, the brakes immediately released!"

I think the ABS module is causing the brake overheating problem.
What do you think, or has anyone ever experienced a symptom like this before?

First, we need to retrieve the error log, and then we can proceed.
I think there's a valve that's stuck.

Hello,

Error memory is empty.

Tax device number: 4Z7 907 389.
Encoding: 06353
Bosch Part Number: 0265 202 403

Where do you think the valve is located? I mean, not in the electrical section where the coils are, but probably inside the hydraulic block itself, right? And is it possible to disassemble it to check it?

In the Motortalk forum, there are several 4B drivers who have experienced the same issue.

Hello,

I'm getting the Bosch ABS hydroaggregate tomorrow (net price: approximately €700).
I hope this will work. I will let you know.
Today I disassembled the engine block and wanted to see if there was anything to take apart. Unfortunately, I didn't get much further than removing the pump and unscrewing the control unit. I would have liked to disassemble the valves. Does anyone know how to remove the valve stems? Are they perhaps just threaded in or something? Maybe someone here has opened one up before and can help me. Thanks.

Hello,

Can anyone tell me what the function of the pump located under the ABS unit is?
Part number: 8E0 614 175E - The description is "Hydraulic pump with electric motor".
What is this pump for, since there's already one on the ABS unit? (Maybe it's only for all-wheel drive vehicles... or...)
Best regards,

luiggi wrote:

Can someone tell me what the function of the pump located under the ABS unit is? Part number: 8E0 614 175E - The description is "Hydraulic pump with electric motor". What is this pump for, since there is also one on the ABS unit? (Perhaps only on all-wheel drive vehicles.........or....)

This is the booster pump for the ESP (Electric Submersible Pump), which generates the pressure required for an ESP control system.

Hello,

Thank you for explaining the pump.

In the meantime, I also replaced the ABS unit, and it's working now. The problem causing the brakes to lock up was the hydraulic unit.

Before I replaced these, I read the error memory again, and I suddenly noticed:

00302 - Relay for ABS solenoid valves (J106)
35-10 - - - Sporadically.

"This error message appeared. I deleted it, and it didn't reappear during the test drive, but the brakes continued to lock up after braking, as previously described."

I didn't search for much longer and then replaced the ABS unit. Now it's working again. It would be interesting to know what the "faulty magnetic valves" error message refers to, and whether it might have been a problem with the electrical part (i.e., the control unit). However, it probably originates from a mechanical issue, since the brakes still locked even with the control unit disconnected, which means the magnetic valves and other components wouldn't be in operation in that case.
What do you think?