Hello, I too am a newbie to this forum but felt I needed to share my recent car problem.
i have a 2007 A4 convertible. I’ve owned it for 4 years and apart from regular servicing I’ve never had the coolant light come on. About 6 months ago, the light came on and I duly topped it up with water. I drove (Regular town driving) for about 3 months and only had the light come on one more time. Within the last month, I was lucky if I drove more than a mile before the light come on. Each time I checked, surely enough the tank was empty. I asked the garage who immediately said it was the head gasket. I really wasn’t convinced as I wasn’t using oil, the oil wasn’t foamy or manky. I wasn’t overheating and I had a pressure test done which were all ok. ...... my lovely husband who has a mechanical background wasn’t convinced either.
‘He discovered that it was a small plastic connector that sits at the back/bottom of the engine. The part number I can see is 06D121133a, it’s called a coolant hose flange. Cost about £12. My husband fitted it but it took around 4 hours because it was so difficult to get to. It’s fixed the problem 100%
The one he took off explains the leaking, it was corroded and looked like it had melted.