Dont worry, the 2 bar cap on these models ensures that any weak spots in your system will be soon apparent. But at least you wont lose coolant between component failures lol!

But seriously, I'd replace it all at once, or as much at a time as possible. I tried piecemeal and I just ended up replacing stuff soon after the other, wasting time and coolant.

JMHO. Others have noted they are on original hoses still, so your call. E46, E39, and E53 are pretty similar to each other, your experience with them is applicable.

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04 X5 3.0i auto
03 X5 4.6is