Welcome Samsonite. Give a rundown on your X5 for everyone, as this will make it easier for folks to weigh in with advice. Most guys put the year, model/motor, mods, etc in their signature.

The sunroof and it’s issues, for one, has been dissected many, many times on the site so you can probably get working on that without waiting for guys to weigh in. Make sure you know which one you have, pano, or standard one. Loosing coolant could be a number of things and there are also some excellent threads here on the same subject, depending on which motor you have. And finally, there are several fairly recent threads on heating and cooling issues/loss which you may want to check out while waiting for smarter guys than me to weigh in. Very likely your issues have been fixed and commented on already. Often with step by step posts and pics.

Coolant loss is always worrisome. Have you looked at the oil, and coolant for cross contamination?

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee