Replacing Coolant Temp Sensor A6 4.2 C6 Body

[ebrummett]

I was trying to solve 3 issues; 2005 Audi A6 (C6) 4.2 Quattro - Check Engine light on - Temp gauge on dash not registering at all - Rough idle - Electric fans on even when eng cold All the above were solved by changing the Coolant Temp Sensor located on the rear of the block closer to the passenger side cylinder bank. The hardest part for me was locating the sensor. Because I read it was on the passenger side, I removed the air intake tube and couldn't see it. There are a couple other sensors there but they didn't look right. So I searched online some more and then went back. The only way you can see the darn thing is with a drop light or flash light but from standing on the DRIVERS side of the car. Go figure. To get at it, I took off the rear plastic cover, I put a step stool at the nose of the car, I used two folded towels and placed them on the intake. I had to get up there on my knees, (no lie) and could barely get my hands in there. Smart thing to do would probably be to drain the coolant, I didn't but I bought a new gallon from Audi knowing I'd lose some. I lost 3/4 of a gallon. So back to the sensor, to remove the clip, just start it with a flat head screwdriver then pull off by hand. If you try to just pop it off, say goodbye to it as you will have to drop the pain in the neck splash pan to retrieve it. I bought the sensor, O-ring and clip, it's worth it. So now that the clip is out, wiggle the sensor out. The only thing supplying resistance is the o-ring. Once the sensor comes out, ensure the old o-ring is on the sensor, if not, poke your finger in the block housing to get the old o-ring out. You can do this while you watch your $22 a gallon coolant splash on your garage floor ;-). Next, disconnect the electrical connection. Install the new o-ring, and install. Make sure it's a nice and snug. I tried installing the first time with the electrical connector, but I couldn't get a good feel that it was inserted correctly. Just make sure you see how it is keyed and it's easy to connect last. Now getting your hand in there to re-installed the clip is a pain. I had to do with my left hand. But once the clip is on there you can re-attach the connector. Before you think your done, just add some coolant with a flashlight on the new sensor and check for leaks. No leaks, button things up. Now the sucky part is I thought you could just fire the car up and the gauge would start to work along with the check eng light extinguishing and electric fans staying off but nooooo. Now I happen to have a Vag-Com VCDS by Ross-tech so I had to connect my laptop to the car. As soon as I cleared the eng fault, bang, elec fans shut off, check eng light shut off and the gauge was working. The rough idle went away too because the car always thought it was cold (dumping excess fuel during its never ending warm up period)The sensor never told the ECU it was warmed up and to back off fuel flow. Hope this helps and good luck. Eric

[pcamaj]

Originally Posted by ebrummett

I was trying to solve 3 issues; 2005 Audi A6 (C6) 4.2 Quattro

- Check Engine light on
- Temp gauge on dash not registering at all
- Rough idle
- Electric fans on even when eng cold

All the above were solved by changing the Coolant Temp Sensor located on the rear of the block closer to the passenger side cylinder bank. The hardest part for me was locating the sensor. Because I read it was on the passenger side, I removed the air intake tube and couldn't see it. There are a couple other sensors there but they didn't look right. So I searched online some more and then went back. The only way you can see the darn thing is with a drop light or flash light but from standing on the DRIVERS side of the car. Go figure. To get at it, I took off the rear plastic cover, I put a step stool at the nose of the car, I used two folded towels and placed them on the intake. I had to get up there on my knees, (no lie) and could barely get my hands in there. Smart thing to do would probably be to drain the coolant, I didn't but I bought a new gallon from Audi knowing I'd lose some. I lost 3/4 of a gallon. So back to the sensor, to remove the clip, just start it with a flat head screwdriver then pull off by hand. If you try to just pop it off, say goodbye to it as you will have to drop the pain in the neck splash pan to retrieve it. I bought the sensor, O-ring and clip, it's worth it. So now that the clip is out, wiggle the sensor out. The only thing supplying resistance is the o-ring. Once the sensor comes out, ensure the old o-ring is on the sensor, if not, poke your finger in the block housing to get the old o-ring out. You can do this while you watch your $22 a gallon coolant splash on your garage floor ;-). Next, disconnect the electrical connection. Install the new o-ring, and install. Make sure it's a nice and snug. I tried installing the first time with the electrical connector, but I couldn't get a good feel that it was inserted correctly. Just make sure you see how it is keyed and it's easy to connect last. Now getting your hand in there to re-installed the clip is a pain. I had to do with my left hand. But once the clip is on there you can re-attach the connector. Before you think your done, just add some coolant with a flashlight on the new sensor and check for leaks. No leaks, button things up. Now the sucky part is I thought you could just fire the car up and the gauge would start to work along with the check eng light extinguishing and electric fans staying off but nooooo. Now I happen to have a Vag-Com VCDS by Ross-tech so I had to connect my laptop to the car. As soon as I cleared the eng fault, bang, elec fans shut off, check eng light shut off and the gauge was working. The rough idle went away too because the car always thought it was cold (dumping excess fuel during its never ending warm up period)The sensor never told the ECU it was warmed up and to back off fuel flow. Hope this helps and good luck. Eric

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