Definitely check the hoses.

I've got a 03 4.6is over here with about 25,000 miles on it that I had to replace a coolant hose on (burst hose). Replaced all the cooling system hoses while we were in. That was about 3 months ago.

Just recently replaced the expansion tank on that truck (pinhole leak). It's still at less than 30,000 miles I think.

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04 X5 3.0i auto
03 X5 4.6is