[sundiz]

For few years my car had lost a minimal amount of coolant during a long period. I had topped up the reservoir maybe once or twice during a year. I went for a 2000km road trip and before I left everything was fine. When I got back home I noticed that coolant was at minimum level. I topped it up. I was a bit worried about sudden loss of coolant. Drove another 300km and the level had dropped 1cm. No signs of actual leak. Everything was dry but still some coolant went missing. Also no smell of coolant in the exhaust. Got a new cap for expansion tank as I thought that could be easiest and cheapest fix for 5€. Luckily for me new cap fixed the issue. Just drove 600km with new cap and coolant has stayed at the same level. First cap failure for me...

[Shambles]

Amazing isn't it? One small, tiny piece of a big puzzle...

[The Gonz]

Very sensible first step solution. Start with the easiest, cheapest fix.