Coolant temperature sensor replacement

[CHAUHANspeed]

I got a check engine light this weekend with a code of p2181 - and I also noticed my gauge hasn't been very accurate recently..I diagnosed the issue of having a bad CTS.

However, after reading numerous threads on how to replace the CTS on the B7 A4, I am confused a little. There are mixed answers in bunch of threads and I figured I should clear this up.

My question is, do I drain the coolant before I pull the sensor out or should I just pull the sensor and install new one?


http://www.audizine.com/forum/showth...=1#post7368820
http://www.audizine.com/forum/showth...ical-Questions

sorry in advance if I missed a thread that explained this in my search of Audizine.

[jimrobbington]

You can probably pop it out and back in without draining, but how big a mess it will be? Not sure. I drained the coolant for my thermostat replacement, and some still came out when we pulled the sensor.

[Charles.waite]

I would drain the coolant. If it hasn't been changed in a few years it probably needs a refresher anyway. G12 isn't that expensive anyway.

[mcpcartier]

I'd drain the fluid, but there will still be coolant up there that will make a mess when you pop it out. Just the joys of working on the cooling system.

[bman005]

I'd replace the thermostat since that's whats most likely wrong with your car. The sensor rarely fails in any other way than an open circuit which gives you a sensor resistance fault. Check freeze frame data if you have it. If the coolant temp isn't -40C or something extremely cold like that you need a thermostat.

[CHAUHANspeed]

After doing more research, i am also leaning towards the thermostat! This job seems time consuming!

[Charles.waite]

After doing more research, i am also leaning towards the thermostat! This job seems time consuming!

Not really. Longest part for me was waiting for the coolant to drain.

http://www.audizine.com/forum/showth...ical-Questions

[bman005]

After doing more research, i am also leaning towards the thermostat! This job seems time consuming!

Not really. Longest part for me was waiting for the coolant to drain.

http://www.audizine.com/forum/showth...ical-Questions

I'm gonna agree with Charles on this one. I did mine over my lunch break

[J.Owen]

Also, I have to check on the B7 since I haven't done the CTS yet, but usually you can unscrew the reservoir cap, squeeze upper rad hose and replace reservoir cap while still squeezing rad hose, remove and replace CTS. Squeezing the hose will create enough of a vacuum in the system that you can replace the sensor without losing any coolant.

[CHAUHANspeed]

Also, I have to check on the B7 since I haven't done the CTS yet, but usually you can unscrew the reservoir cap, squeeze upper rad hose and replace reservoir cap while still squeezing rad hose, remove and replace CTS. Squeezing the hose will create enough of a vacuum in the system that you can replace the sensor without losing any coolant.

Thats a cool trick if it works! what thermostats do you guys usually recommend?

[mcpcartier]

Thats a cool trick if it works! what thermostats do you guys usually recommend?

? I don't think you have a choice.....it's an assembly. I don't think I understand the question.

[mcpcartier]

Not really. Longest part for me was waiting for the coolant to drain.

http://www.audizine.com/forum/showth...ical-Questions

I'm gonna agree with Charles on this one. I did mine over my lunch break

You guys are good. I fought with everything doing the thermostat. I think I could do it in under 2 hours next time. It takes me 20 minutes to get it jacked up, get the belly pan off, and start draining the coolant. I'd be luck to have the old one out in less than an hour.

Either way, it's not a difficult job.

[IKE20VA4]

I just did this today, so I can clarify a few things.

1) You're going to have about 16-20 oz of coolant gush out when you pull the old coolant temp sensor.

2) When I pulled mine, the o-ring was left in the hole, so I wasn't able to jam the new one in right away. Had to fish out the old o-ring and then the new one went in fine.

3) At first the CTS was hard to find but once you find it, access is pretty easy.

[CystmX]

I just did this today, so I can clarify a few things.

1) You're going to have about 16-20 oz of coolant gush out when you pull the old coolant temp sensor.

It gushed out even though you drained it first?

[IKE20VA4]

I didn't drain it. So I don't know. I think I read that some will still come out even if you drain but don't quote me on that.


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[pDubs]

I got the p2181 this week also. After some research I'm thinking it's the thermostat. Gonna have to knock that out next weekend. My temperature gauge isn't really going above 1/4, normally around 1/2. Is it bad if I drive the car until I can change the thermostat?

[PedroPickleB7]

Another common issue that people should look out for. Bump for a spring cleaning maintenance check! Thermostat check!

[Sanjman]

Thanks..... Title is misleading a little. Fluctuating temp gauge is usually thermostat. I would not drive the car for a long period of time as your engine may try to over compensate the wrong readings from the tstat and you could over heat very quickly demolishing your head and building oil sludge (oil consumption can get very bad).