Noticed while driving that the temp gauge said 50, and then all of a sudden shot right up to 90, then right back to 50. It stayed there for a while, eventually shot back up, just sort of fluctuated back and forth every so often. Now that I'm parked it's staying at a steady 90, hasn't moved. (spoke to soon, as soon as I types that it dropped back to 50)

Any ideas what this is caused by? My coolant is full, I see no leaks...hmmm

 

that's your coolant temp. Pretty strange. I'd be keen to check further into that. I'm sure it's the sensor or something rather than the gauge being fkt.

got vag com?

 

there is a warrenty extension for the coolant temp sensor in certain audi models under 10 years old and less than 160k my 2002 a4 3.0 was covered parts and labour.

i had a post on here about but cant find it any more.

 

sounds like a faulty coolant temp sensor, it was a very common failure and is a pretty easy fix, open the hood and look at the back of the head and see if it has a green top, if it doesnt then it most definately needs to be changed