posted this already in the general a4 forums so sorry for reposting
changed my cts and coolant yesterday, was having issues with an iregular temp gauge.
after changing both took car for a long drive temp gauge rose half way and sat there perfect!!!!!!
however now the problem once i switch on the heater the temp gauge drops and the heater is blowing cooler than normal.
tried bleeding from the heater hose entering at the firewall however it did not fully fix the problem still drops a bit and still cooler air.
any suggestions?try rebleeding?
any help greatly appreciated
its a 2002 1.8 a4

 

You need to bleed more. What i do is leave the cap off the reservior and rev the engine. The coolant should pull down out of the reservior, and when it does fill it up and re cap it. Keep doing that until the coolant doesnt come out of the res.

 

so i tried bleeding and it took most if not all the air out,car heats up significantly better however the temp gauge still drops and hovers above and below the quarter mark once the heater is turned on????
should i blow out the heater core??

 

Sounds like it still needs more bleeding. Just keep an eye on it and whenever the res is low fill it up. Mine took quite a while to get bled out.

Did you use G12 coolant?