A2 1.2 TDi - Pressure accumulator replacing with pics and Fluid question

Hello,

Was getting only one or two gear changes before pump restart together with a somewhat jerky actuation of the clutch. One morning the hydraulic pump had to work for 2 minutes before we could start the car, so I ordered a new pressure accumulator from this ebay store, bought VW hydraulic fluid - (P/N: G 004 000 M2) and changed it yesterday.

Here is an how to. I would appreciate your comments to make it accurate if something is not correct.

- Remove the bonnet (prepare a suitable rest location for it)

- The hydraulic unit is on the right side, just alongside the coolant expansion tank:


- Disconnect the water drainage tube (mine was not connected I am staging the pic) and move it aside to gain some more space.


- Diconnect the coolant level sensor connector. it is easy to do by applying pressure with your thumb on the trigger:


- Using a 10 mm socket with a ratchet and long extension is easy to get to the only nut holding the coolant expansion vase (don't drop it once loose ):


- Whiggle the coolant vase out of it's holding pins and move it aside (no need to disconnect any tubing here).


- (??? is this step necessary???) With the help of a screwdriver disconnect the hydraulic unit connector (check this thread if in doubt of how to deal with the Audi electrical connectors ):


- Next you're gonna remove the hydraulic accumulator. Once you untighten it, the fluid level will rise in the tank and it is a good idea to prepare for some overflowing (get a towel around it).

- With a 24 mm spanner (or an adjustable wrench) loosen the hydraulic accumulator and unscrew it (in my case, I am staging the pic again as it was only finger tight) :


Will continue...

- Remove the hydraulic accumulator by unscrewing the rest by hand, control the overflowing fluid if that's the case.:

- Remove the old accumulator tank and install the new one. Don't over tighten it. Correct torque is 40 Nm, with a big spanner it is easy to go beyond that.


- Close the hydraulic fluid tank (once you install the new accumulator the fluid will lower).


- Re-connect the hydraulic unit connector

- Re-install the coolant vase, (tighten the 10 mm nut, re-connect the coolant level sensor connector)

- Re-install the drainage tube.

- Put the bonnet back on.

I think this would be "normal" procedure for changing the pressure accumulator. Please feel free to suggest any modifications.

In my case, I think I have a problem that I'll ask about in the next post.

Nice work, clear and helpful guide so far. Must say, the allure of the 1.2 TDi is strong!!!

Carlos,

From memory, the torque for the accumulator is 40Nm. You will need a 'crow's foot' to do though. Also when you remove the accumulator, the oil doesn't normally overflow if you unscrew it slowly.

RAB

Thanks for the comments, I'll update the tightening torque above.

My procedure was not entirely as above. As it was visible in the pics, the hydraulic fluid was far from clear: milky appearance with lots of trapped air. I decided to suck all the fluid in the tank:




I've let a sample rest overnight and this was the result:


As I reported, the big water drainage pipe above the hydraulic unit was not in its place, Audi dealer was the last to remove the bonnet this was some three months ago. All the water collected by the windshield will descend directly on top of the hydraulic unit and my guess is that water got into the tank by the venting hole in the tank cap.

At www.a2-freun.de/ there is a report of a similar occurrence and the victim decided to take the hydro unit out to purge it and suck as much fluid out of the lines as possible (at least that's what I gathered from the google translation). I was scared to death to end up with a cavitating pump and lines full of air with no bleeding points or procedure. But after considering the effects of letting the hydraulics work with that sludge I decided to try the same.

Today, I took out the pump unit and disassembled the expansion tank, the electric motor and the pressure tank out, sucked all the old fluid and injected new one before reassembling.





Fishing the old fluid out of the lines involved a piece of wire insulation, thin enough to be used as a catheter and a syringe. I used the same contraption to inject fresh fluid in the lines to avoid trapped air.





I am sure that contaminated fluid will have remained in the lower parts of the hydraulic circuits (I guess that's the clutch slave cyl), I'll keep looking for a way to drain it that won't leave me with air in these circuits. Also, there were signs of fluid leaking around the electric motor on the hydro assembly. I've heard that there is a kit of gaskets available, will have to investigate that. At the end of the job today, doing the "Tiptronic testing with engine off" i got the previous 3 shifts before pump starting on the 4th. I would be more happy with the 6 or 7 that the Lupo 3L guys regularly report, but in any case I am more relaxed now that I took most of the contaminated fluid out and gained a bit more knowledge about the 1.2 beast.

Cheers,

Carlos

Good job!
How long did you leave between disabling the control unit's electrical supply and removing the accumulator?
The overflow could be caused by this.
When I removed my accumulator there was a little dripping from the accumulator but no leakages. This could also be temperature related. Mine was done in -5c.

Out of interest did you see the date of manufacture on the previous accumulator.
When I changed mine a couple of months ago the production date and lack of a supplementary sticker led me to believe that it had lasted over 225,000km and 12 years!

Be careful with the hydraulic control unit plug it is a pain to change....



I only noticed my plug was broken when I needed to do a basic setting and found it was held in place with cable ties. It was a painful 3/4 hour to change it even using the Sealy cable ejection tool (which by the way is a life saver if you ever need to change a connector on your car!)

Hi John,

Thanks for the props and the heads-up regarding the plug. I took it out when I started the job, not long before removing the pressure accumulator I would say. The car had been used a few hours before but when starting the job I entered the car through the passenger door to avoid the pump running. Also, I took it slow unscrewing the pressure tank but overflow occurred nonetheless. I guess it had to do with the fluid condition. It had lot's of tiny bubbles of air, so volume increases. Temp was about 20 C. (-5 C I would be by the fireplace not tweeking an A2 )

Speaking of temperature I warmed the new fluid before injecting it in the lines to make it thinner. Tried first in the kitchen's microwave but it didn't work (how about that?) had to resort to water bath (bain marie).

Previous accumulator shows "02127637 14/01/1 M2WC100127" haven't compared with the new one, don't know if the date might be 2001 (date of car manufacture) but I have looked into the paperwork and I can't see a replacement fit in any of the services. It might well be the original one (13 years and 180.000 km).

I have a few more pics that can be helpful if someone is considering this job: http://cj.smugmug.com/Other/Audi-A2-12-TDi-/

Another tip if you don't want to undo the connector is to disconnect the battery.