Rear coolant flange??

[OreOOO]

So I have owned my a4 for about 2 months now and noticing some funny coolant symptoms. First of all I believe the thermostat or coolant temp sensor is gonzo, constant coolant temp fluctuation. And just noticing only when it's very cold out the rear coolant flange seems to be leaking but only off one of the hoses. Anyone else experienced this? Do I need a whole new flange or could it just be the hose??

Video link
https://vid.me/11nA

[Charles.waite]

I bet your thermostat is bad, causing the temp fluctuations. Both of my b7s have had their thermostats fail around 60k miles. I tested the thermostats and they were opening at 50°C instead of 80°C. I would recommend going with Behr brand.

As far as the leak I don't really know. Pics of where the leakage is coming from exactly would probably help.

But replace that thermostat. It's a pretty easy job.

[Low and Behold]

I agree, try the Thermostat first. Its easy.

If it turns out to be the rear coolant flange/temp sensor, you'd benefit most from replacing the entire flange. I just did this over the weekend and its annoyingly difficult.

[dalmation53]

you can check your coolant flange just let the car warm up and let it cool down for 30 mins and then see if your transmission on the top behind the engine to see if is pink gunk or you can actually reach in there and it would be wet. but let the engine cool first.

[B72011]

Pray on your knees it aint the flange. Big Big pain or big $$ in your future with that piece. My advice is pay someone $350 to replace it.

[OreOOO]

I posted a video above. I have looked in there a bunch of times but it needs a cleaning from the valve cover leaking before I can see the coolant caked up. But it definitely is dripping back there. Looks almost like its the hose going to the heater core, the flange is pretty dry actually.

[Charles.waite]

Coolant leaks tend to look white and crusty. That looks like oil to me...

[Sheekie326]

I had oil leaking like that, all over the top of my transmission in my 07 a4. Turned out to be a bad vacuum pump.