Have a 98 a4 2.8. Sometimes the engine temp gauge is fine and others it is not.Staying on cold, needle not moving. Where is the sensor? Also the temp display on instrument panel will read -40 then work up to the real temp. Kind of a pain when the AC turns off. Where is that sensor?

 

Engine coolant temp sensor. It's behind the passenger side head on the black pipe that runs behind the motor and connects the two heads. It's about $20 and 15 mniutes of swearing to swap it.

Right behind the bumper in front of the bottom of the radiator.

 

Thanks, where can I find the part #'s?

 

Don't need it. Call NAPA or any of the others. If you have a blue one you need a blue one. If you have a green one you need a green one. That's about all there is to it. Or, take your VIN# to the dealer and pay an extra $20 for it.

 

theres a square one and a round one. I have seen a green square one and a blue square one. The round ones are just green. thats the only difference.