ok so ive got a 99 a6 quattro 2.8 and this happenes every other time when im using the car, the temp guage will be all the way to the left as if its cold and then sometimes when its like this it will after the car is completly normal and running at normal temp, the dial will move about a quarter way up and stay there, then other times it will not move at all, but the car runs just fine and has never had a problem, this has been goin on for a few months now, this happens every other time i use the car, and other times it works just like normal with the dial in the half way mark, how it should be, so im guessing this is the coolant temp sensor, my friends a4 did this too and he replaced it himself, but hes got a 1.8 and i would like to know if anyone knows where this is on the 2.8 and if its hard to get to, if anyone has pics or anything it would help alot.

thanks

 

its down under the intake elbow on the pass side @ the rear of the motor, near the throttle body... probably has a green top, or blue or black, i forget

its kind of a pita but with patience, its not that difficult of a job

 

Here are some pics.

https://www.audiforums.com/forum/members/hxgaser-45299-albums-cts-2-8-atq-110/

When you replace the CTS, make sure the engine is COLD, and loosen the reservoir cap to release the pressure. Retighten the cap and replace the CTS. IF you have small hands, you should be able to replace the sensor just by removing the intake hose and loosening adjacent rubber hoses.

 

hand size will be an important factor when replacing the sensor on the 2.8l, my advice would be to place a rag under the sensor to catch any parts you might drop like the u-clip, also make sure you get the old o-ring out of there, good luck

 

ugh god i fear doing projects like this. but thanks for the help, so the first pic on that is of the sensor i know this now, but is it where i have to take the air box off to access it?

 

You don't have to take the whole air box off. Just the flexible intake runner between the air box and the throttle body. Just loosen two hose clamps and you are done. I also removed a few rubber hoses from plastic clamp on the fire wall to get more space. Really the job did not take more than 20 minutes. Just make sure the car is cold, depressurized, and the cap closed. Also make sure the sensor is seated properly before putting in the clip back on. And be sure to remove the old rubber o-ring and replace with new like AutoUnionFan said.

 

I'm working on this right now and haveing a hell of a time, maybe my hands are two big, ha-ha. this would be alot easier if I could remove air intake elbow, how the hell do you get it off?

 

My 95 has actually two coolant temp sensors.
One is a switch (3 prongs connector) - located indeed under the air box, and the second one is the actual sensor (two prongs connector), located on the driver side, right by the bleeder.
The switch is much bigger than the sensor.
You may want to check the other one as well.

 

I have a 99 A6 2.8Q. When i was pulling out retainer clip the top broke off leaving the ends still inside. They are too short to get a hold of and still hold the sensor in to well for me to just pull it out. Any ideals how to get the broken parts out?