Just bought a 2000 A6, 4.2 V8 engine. The temp guage works but keep droping back to 0 on and off while in use. I think its most likely a connection problem at the sensor, but don't know where its at! any help on that one? Also didn't get the manual with this car and would like to find one if I could.

I just put my 2001 S8 in the shop for the same thing .. . will let you know what the mechanic says ...

The sender is on a crossover pipe between the banks at the rear of the engine, towards the right hand side.

I had to change a vacuum hose on the secondary air injection valve a month or so ago - after I was done, the coolant temp gauge was dead.

I moved the electrical connector back and forth a few times - that fixed my problem.

and the stinkin' car is running too hot!!!

Needless to say, was not pleased that they let me take it off the lot in that condition, so tomorrow am going back.

But - what Rob says - if it's giving you weird readings, then there's something wrong with it - mine works perfectly now, just so happens it does't like going to 120.

You can also hit the recirc+up arrow combo to get the instrument cluster reading - scroll through to setting 102. Mine was stuck at 30, would go up to about 90, then back down to 30.

When I started the car, the needle would jump to around 90 and then slowly go back down - weird behavior, one time it finally registered while I was driving home, just off the freeway, and the needle was up in the high limit, which I'm told is a big no-no on these cars - so made the service appointment.

Theory now is thermostat - which is behind the timing belt ... so my $400 job is now $1400 or so . . . .

Car has 40k miles on it, if that helps you out any . . .which seems really odd to me to have a thermostat go out that quickly.

Good luck!!

I think your on thr right track Rob, thanks for the infro. on where it is.

Replaced the thermostat - car runs within tolerance - did the timing belt for good measure - everything else looked solid - we'll see how we do for the next week or so -

Love having the gauge back - coolant sensor fix . . .

Good luck!