Sounds like your thermostat is stuck open. $20 part. If your timing belt and water pump haven't been replaced recently, just have it all done as one complete service.
My 2001 S4 warms up super slow (water and oil temps) and usually only to the 1/4 marks on both if i let it idle for a few minutes. After any driving it goes back down.
I think this is because the non backflow valve/check valve is stuck open and is allowing the water to continually circulate.
Can anyone confirm? Part numbers or info on where to find the valve would be very appreciated. Thanks in advance guys!
if your car is at second timing belt job interval (150-160k) do valve cover gaskets with cam chain tensioner gaskets and pads. I've seen a lot of these pads wear out at the second timing belt interval. Blauparts' valve cover gasket kits now come with cam chain tensioner pads