Regarding my 1.5 non turbo petrol:
I have read the manual and it states: "Check the level in the reservoir by looking at it side-on. The fluid must lie between the MIN and MAX marks". Its dark and I've only used a little torch whilst having a little look on my lunch break today but I'm damned if I can see any marks on the bottle!
I actually thought the engine was running too cool, not too hot as it sits at around 80 degrees and maybe needed a new thermostat. However, the bottle looks empty to me. I see from this advert for a second hand one the markings are right down the bottom-- weird. Can you actually see it from up top when the bottle is installed?
How should I really check the level? Make sure the radiator is full and then get the "expansion" bottle to the right level? Weird non-closed system but I vaguely recognise the non-pressurised bottle type as my wife's Mini had similar.