first off, yes i did read the diy thread for replacing the thermostat, im makin a new thread to discuss the issues im having and to not get lost at the bottom of that thread.

i've been having an issue all winter with my car maintaining the 'normal' operating temp. this was a harsh winter for me and i understand the temp. fluctuations when the air temp is -15f but its still doing it when the air temp is 45-55f. i have an obdII reader and the torque app and was watching the coolant temp. while driving today, it stays about 172f (just below the middle line on gauge) when im goin between 45-55mph. over 60mph and itll stay on the mid-line (176f apparently). the temp. also dropped 10 degrees rapidly when i switched on the heater and put it on HI. i have some g12 for topping off and have been watching the reservoir level, no changes there. oddly, no CEL codes have shown up yet and its not overheating either....


TL;DR
the coolant temp. drops every time i drive below 60mph, wtf?
is the thermostat dirty? stuck open slightly? worn out?

 

Hum, really going to be no help here. My car stays about mid-line all the time. Doesn't seem to matter the outside temp or the speed I am driving. Usually if you have a cooling issue the slower you drive the higher the temp gets. If I was having this issue I would check the following:

1. Replace thermostat
2. Check temp sensors for the cooling fans are working correctly (not cutting in at too low a temp).

I take the heat from the heater is fine when you run it? If your thermostat was stuck open I would think that would blow cooler air.

 

yea, idk why its running colder... my buddy say check the fan and make sure it doesnt run constantly, havent had much a chance to watch that yet though. the heater seems to work fine, i dont crank it up much past 75, even in the winter, so it does the job for me still. like i said, no cel yet and no serious problems. just wanna get ahead of any issues, but dont wanna tackle the thermostat job if i dont have to.

 

Since you were asking about symptoms, I am getting the 2181 "cooling system performance" CEL code, and my A4 runs cold..I have not used the reader on it to get the coolant temp, but the gauge hovers near the first mark, not in the middle as usual before the CEL.

Other than the annoying CEL I need to keep resetting, I am not experiencing any other issues related to the t-stat, or the engine running cold. I am planning to replace the t-stat when I do the timing belt..the dilemma currently is if I can tackle this myself or not!!

 

well, winter is coming , and i still have the same issue. does anyone have advice for this? i dont have the time or money to start guessing and replacing **** if its not the real problem. im so confused as to why the CEL isnt on yet... the worst dip in temp seems to be about 20 degrees below normal. this is after driving for 30 min and normally my car is up to temp in about 10 min or less in the current weather. does anyone know what the actual threshold is to set off the CEL?

 

Change the thermostat. It isn't expensive to do yourself. Just get the right brand, mahle baher or genuine Audi avoid the Wahler brand it has been known to leak after application.

Or change the coolant temp sensor on the coolant flange

Both can cause erratic readings.

From what I personally remember tstat triggers the malfunction code then the cel will display. It did have erratic behavior and p2181 code before a MIL/CEL was on(i have vagcom). Threshold? Can't give a definitive answer, but once the malfunction passes intermittent then it will trigger the mil.

Coolant is going to be refilled for both procedures.

 

hmm thanks for the info. ill have to do more research

 

Nice information dear. I suggest you to visit mrcluth best trusted dealer.

 

My A4 didn't show a code when the thermostat quit. Matter of fact, it's logged multiple codes that should have flagged on the dash readout, but didn't. I just knew from the crummy heating that it was the thermostat. Happened in another car. I took it to an auto parts store to have the codes read, and got the 2181 code which pretty much means the thermostat quit.

 

Okay so not sure if anyone is still active on here but, I'm having an issue with car turning on and the fans turn on with it, I put heat to like 80 and max and it blows out cold and also the coolant level was -40° when I checked it with OBD11 I assumed it was the Coolant Temp Sensor so I replaced that and got a CEL for it I cleared it and still came back, the fans are still running every time I start up car and they don't turn off I'm not sure what it could be at this point the I'm going to replace the thermostat, begging of next week when it comes in hopefully see if that may solve my issue but if anyone knows what is causing this issue please let me know would really appreciate it.