1.2 TDI A2 / Lupo 3L Clutch slave cylinder 6N0142063x

Hello,

Has anybody tried to repair faulty clutch slave cylinder (6N0142063A)? As price for new increased for ~110 euros to ~320€ since 2012

In my case few days ago my car started to put transmission in "safe-mode" after unsuccessful gear engage. On still car I've checked triptronic mode, all gears were working, except 5th, it got engaged but could not be disengaged.
I've checked clutch movement, and saw that it was pulsating in short interval of movement. Checked clutch slave cylinder, potentiometer showed 1.9V in disengaged mode. In engaged mode it was showing values from 3.5V to 3.7V . As I read in manuals, difference should be at least 2V. After some playing with adjustments, clutch slave cylinder stopped responding at all, it's wakes up on after trying to pull it's cable manually. I remember I had very similar situation five years ago, afterwards I've changed that slave cylinder, and gladly doesnt throw it away

Yesterday I disassembled it ( wasn't so tricky as I suspected ), it was quite dirty inside, but all parts seems to be ok ( spring, sealing ring, cylinder ). What was broken is potentiometer linkage to the cylinder's cable, it holds by weak plastic ring. Now it's hard to tell could it be reason to fail in operation. I will try to put that old reassembled cylinder on my car to check does it operates.

Will keep you in touch

Valdemaras

There is a post on the German site about replacing the potentiometer with a contactless Hall Effect sensor (such as is used on the gear actuator):

https://a2-freun.de/forum/showthread.php?t=50969

The trick is to find a suitable sensor that gives a comparable signal at both ends of travel. You will have noticed that the gear actuator is generally longer-lasting than the clutch actuator!

RAB

Update.

Swapped slave cylinders ( that old, which had broken potentiometer holder ), clutch acts the same. So there is two options - or both slave cylinders are still faulty, or problem persists somewhere else. While dealing with cylinder, I found it's hard to move clutch's release shaft with hands, and there is some strange noise. Now I'm considering that maybe problem is with clutch release bearing or clutch by itself ( which was changed ~90k km ago ). I've rejected that my problem could be caused by Hydraulic unit, as gear actuator works well, and there is nothing what could brake with solenoid valve.
Other strange thing, that after hydraulic pump operation, when it generates pressure to 55 bars, hydraulic unit stays operating with very quite humming sound. I thought it should shut down after 5 mins, but no, it was still humming. Sadly, I dont remember was it the same before on running car.

Btw, this is part which was broken on old slave cylinder

Sounds like the release bearing and/or the guide sleeve. Humming is normal but should cease with ignition off.

RAB

UPDATE

Hello,

Firstly, my problem was not caused by release bearing or the guide sleeve. Checked them, both are ok. So main attention was targeted at gear actuator. Disassembled it, bottom selector finger had some loose again, re-tightened and started adaptation process. Visual inspection showed, that 2nd and 4th gears where not actuated, 1st, 3rd, 5th and reverse where OK. Checked bottom finger again, adjusted potentiometer, started adaptation. Results were the same - no 2nd and 4th gears. Then disconnected gear actuator from gearbox and put test again, all gears where actuated. Refitted gear actuator to gearbox - no 2nd and 4th gears again. This meant that mine gear actuator is faulty inside ( one piston does not holds pressure and fails in movement ). So found another gear actuator from Lupo ( ~200k km ), put it on my Audi, and everything went as it should. Also I've noticed that I can achieve more gear changes with single hydraulic pump operation. Probably cilinders got worn more and more until there was insufficient pressure to activate gears. I will try to show my old gear actuator to local hydraulic guru, maybe he will have some ideas to reanimate it

So, now I'm on track, I hope for at least 90k km

Thanks RAB for advices.

INFO

This is my disassembled gear actuator. As I said, problem is with top cylinder/piston, there is pressure leak, which leads to wrong operation on 2nd/4th gear actuation.

When repairing a leak on the gear actuator (not an internal leak), check that the surfaces are flat, otherwise simply replacing the gasket may not work. Use fine wet and dry on a small piece of glass and clean thoroughly afterwards.

RAB