HELP: Coolant temperature fluctuation
 

Hey All, I'm new to the site, have had my 99 A6 for about six months and have had constant problems with my coolant temperature and would really appreciate some advice! Since I have owned the car, once warm, the coolant temp gauge will sit at 90 degrees then intermittently drop down straight to 60 degrees in about 30 seconds. Once in a while it will shoot back up to 90, only to drop down again. I have had the coolant system flushed, which didn't fix it and then replaced the thermostat twice and the problem has not been solved. Any suggestions would be helpful!!

Re: HELP: Coolant temperature fluctuation
 

The car has 2 thermostats did you get them both replaced?

Re: HELP: Coolant temperature fluctuation
 

I did not know there were two. The one I had replaced was the one that is recommended during a timing belt service. After I experienced the same issues I took the car back and had it replaced as I had assumed it was not working properly. Where is the second thermostat located, and how difficult is this one to replace?

Re: HELP: Coolant temperature fluctuation
 

Re: HELP: Coolant temperature fluctuation
 

That was my initial thought too - simply a malfunction of the gauge. However, I do not get hot air through the vents when the gauge drops off to 60 suggesting that the gauge is working fine and there is a problem with the coolant system. I am admittedly not a mechanic and will ask my guy to check that, however are there any other suggestions you may have?

As I am new to the site I just realized that was a link not a response - thank you!

Re: HELP: Coolant temperature fluctuation
 

No Problem yeah that is a link, but the coolant system if the sensor does not function properly and it shuts the gate valve where the coolant passes through you will blow cold air as nothing is flowing through to warm it up. By replacing the second sensor you will have the constant flow resulting in the fix of the issue. hope it works out for you and the sensor is on the medium side of how easy/hard it is to replace, its a PITA (Pain in the A..) to get to.
Enjoy let me know how it works out for you. And Welcome to the site there is a lot of information on here and it is very usefull let me know if any other problems arise

Re: HELP: Coolant temperature fluctuation
 

Thank you for the advice and the warm welcome. One final question - Am I running a risk of damaging anything if these sensors do not get replaced in the next 7-10 days?

Re: HELP: Coolant temperature fluctuation
 

The answer is possibly... the reason I say that is because I do not exactly know if the system pressurizes and forces the liquid or if it just stays around in the block, the risk is pretty high as you can burst some things making it even worse and having to replace cracked hosing, is there any fault codes? You are in Calgary locally? Click on my name and send me a private message we are starting a Calgary Audi Club, so you can join

Re: HELP: Coolant temperature fluctuation
 

Thankfully no fault codes or engine lights on yet. As I mentioned this is something that has been going on since I bought the car - which is otherwise rock solid - and I have had a fault code come up in the past, but nothing of that hasn't been fixed and nothing has suggested a coolant system issue. I have sent you a private message regarding the Calgary Club as well.

Re: HELP: Coolant temperature fluctuation
 

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