I'd consider a slow drip refresh of coolant hoses, tanks and misc bits...whatever the previous owner(s) didn't do in the past 10 years or so. The heat the M62 motors put out is hard on the plastic bits, expansion tank, etc. especially. If you do it all at once you may want to consider a new radiator, if yours is the original. The end caps are plastic and can get brittle and fail spectacularly.

Also, take a good look at your vacuum lines, especially if they have been exposed to slow fluid leaks.

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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