Small coolant leak from expansion tank

[evilbane]

Hi guys, just wondering if anyone could help, I noticed a very small amount of coolant leaking from a small pipe at the back of the coolant expansion tank (the side with the bolt on show). It has some kind of sensor then a pipe attached. I'm thinking the very small o-ring has failed on it so am hoping replacing it will solve the problem. The only problem is I don't know the part number?

 

[NHN]

Maybe it just needs removing & repositioning.

 

[evilbane]

I've tried that, unclipped it and swung the small o-ring around then re-seated it. Still a leak present.

 

[NHN]

Assume the o-ring is on the white plastic pipe of the reservoir, you can buy a kit of rings at Halfords of varying sizes, audi parts usually keep a large array kit aswell.

 

[evilbane]

No, the small o-ring is on the actual plug itself.so will be very hard to replace it without over stretching a new o-ring over the top of the switch. It may be the actual tubing that's leaking. I cant seem to find the part numbers for anything attached to the expansion tank.

 

[desertstorm]

Have a look on Partsbase, I suspect you may have to buy the pipe complete.
Check that you don't have excessive pressure in the system by undoing the coolant top up cap slowly when the engine has just been stopped.

http://www.partsbase.org/audi/audi-a4-avant-a4-eu-2009-12141-coolant-cooling-system/

Karl.

 

[evilbane]

Ye I have the parts numbers now thanks. What do you mean by "Excessive pressure" as I thought the system was a pressurised one (it hisses when you unscrew the expansion tank lid)