Zedebee said:There’s a lot of coolant in the N52, 6-7 litres if I remember correctly. I wouldn’t worry about any harm done from running it half a litre under, but it will need investigating if the level drops again. Leaks from the expansion tank are very hard to see.
Shamefully in my year of ownership my relationship with the coolant has been to look quite a long time ago and think "that looks fairly low" and then another 5 or 7 months going past and actually checking properly and topping it up. Given that I believe it was somewhat neglected by the previous owner between 2021 and 2024 it is possible that it lost 500-600ml over a 3 or 4 year period! I hope so anyway. I will keep a closer eye on it.