Can someone tell me, or possibly upload a picture of where the thermostat is on a 2001 A4 Quattro? I've read where it's next to the water pump and also by the alternator, so I'd like to know before I try figuring out how to replace it.

I'm not getting any heat coming out of my vents, and my temperature gauge stays by the cold reading until maybe 20-30 minutes of driving, and it rarely goes up to the halfway point. Usually only goes up 1/4 of a reading. I usually keep my heat turned off since there's no hot air, but if I turn it on after about 10-15 minutes of driving, hot air will come out, but then quickly turn cool again.

From what people have told me, this is my thermostat, which makes since with the way the temperature gauge is acting.

 

Also wanted to add that I had recently taken the vehicle in to have the alternator replaced. They had to take apart the front of the car.... of course.... so I'm wondering, would air in the heater core cause me to have these symptoms? Neither of the heater core hoses are hot to the touch after driving. I know the heater works with it blowing hot air when I switch it on after driving a little bit, it just goes back to cold air after a few seconds. I've read posts of people having similar problems. Has anyone been able to find a problem other than the thermostat? Granted I'm not very knowledgeable on cooling systems, but would a thermostat control how the heater works? I know it regulates the temperature of the coolant, but if it's stuck open, would it cause the heater to blow cool air? Even when the temperature gauge does get to the mid-range, there's still no heat blowing out, so that makes me wonder why it's not working when the coolant temperature is where it should be.

 

Since last replied was 2011 and never get to see what the result you got. So what was it since I have exactly same car as your, 2001 Audi A4 Quattro 2.8. So was it thermostat becuz I do believe it's thermostat since I had the same issue on other vehicle. Hope to heard from ya!

 

If your temp gauge is not going to the middle, and if it gets even lower when driving, it is indeed your thermostat. on the 2.8, the thermostat is located behind the water pump and usually done when doing the timing belt job, since it needs to be removed to get to it and the front of the car needs to come off.

AIR in the heater core will NOT cause your temperature gauge to bounce like that. Usually it is the thermostat.

 

Thanks markymarc! I went ahead and torn down the front bumper and all the way to water pump to replace thermostat and I also flush out both way the heater core. It's been 1 week so far and it blows like a fireplace!! Whew! My first time and passed in first try!