Hydraulic clutch on Audi A3 8PA 2.0 TDI not disengaging

Hello,

I'm experiencing a problem where the clutch occasionally doesn't disengage; in those cases, the pedal doesn't return.

Brake fluid level is okay, and there are no visible leaks anywhere.
Everything is dry on the clutch master cylinder located in the passenger compartment and engine bay, as well as on the hoses leading to the brake fluid reservoir and the slave cylinder.
If you keep your foot pressed fully on the clutch pedal for 5 minutes, it will remain perfectly disengaged, and the pedal will return to its normal position.

Today I bled the clutch system, but after driving for 5 km without using the clutch pedal, it was almost completely depressed again and wouldn't return fully.

Has anyone ever experienced this before, where the system draws air without any apparent cause? What about the seals on the hose between the donor and receiver; are they known to become hard over time?

Best regards, Rainer.

The initially proposed approach of having a local workshop carry out the repair was rejected.

After some people were on vacation, others didn't have time, and the remaining workshop told me, with a clutch kit costing 5 times the usual price, that they didn't want to do it, I decided to do it myself.

And if I have to dig a hole under the car and the hoses bite my teeth off.

First, the parts that make sense to replace anyway will be exchanged, such as the clutch master cylinder up to the transmission. If everything is good at that point, great. Otherwise, the rest of the parts will also be replaced. For the total price mentioned, I would have to work for many weeks in order to have anything left over.

Hi Rainer,
If there's a leak to the outside, you would lose brake fluid. Can either of the pistons, in the master cylinder or the slave cylinder, occasionally become completely free and move all the way through?
hg
Herbert.

Hello Herbert,

"What surprises me is that the brake fluid reservoir wasn't completely full, but I couldn't find any brake fluid anywhere where it shouldn't be."

Sure, but if things go wrong, this fluid will leak out of the clutch bell housing, and the engine cover will prevent it from dripping onto the floor.

To me, it feels like the master cylinder is passing through. When bleeding at the connection to the slave cylinder, air bubbles also appeared.

Best regards, Rainer.

Hi Rainer,
See also here for information on bleeding (removing air):
/viewtopic.php?t=30562&highlight=brake fluid

There must be enough fluid in the chamber that connects to the clutch.

The clutch slave cylinder may be removable for visual inspection while still connected to its hose.

My suspicion would be that the inlet on the slave cylinder is not sealing properly during clutch operation.

hg
Herbert.

Quote:

There must be enough fluid in the chamber that connects to the clutch.

"Thank you! I had some doubts about that when the error appeared. However, it's possible that after driving for a few kilometers, the fluid level decreased due to wear on the lining but was still within an acceptable range."

It certainly wasn't helpful that I had to brake sharply several times in quick succession just before the error occurred, due to traffic conditions, which likely caused the fluid in the reservoir to slosh forward and simultaneously depress the clutch.

Let's start by being generous.

Thank you for your feedback!

My brother has a workshop that's somewhat set up near you; feel free to contact him if you're interested, and I'll send you his number via private message.

Hi!

Yes, always replace the donor cylinder first when dealing with such unusual problems.
That's the fastest way, and it's also the cheapest.
and often the cause as well.

"I'm experiencing the same issue on my 8PA Quattro."
It would be great if it were that "easy" to solve.

Unfortunately, the receiver cylinder was defective (leaking).

[Translating...]

Also wahrscheinlich Getriebe raus, Mist, das würde ich mir gerne ersparen...