At how many miles should a water pump be replaced on a 3.0 X5?

M52/54 water pumps fail pretty regularly in the 70-100k range. If you've made it to 100k and never replaced it, just do it, it'll leave you stranded soon enough (mine lasted all the way to 135k, but I'd rather have been able to choose the time of replacement instead of it choosing the time).

While you're at it, replace the expansion tank (I didn't heed my own advice and the tank ruptured 3 weeks after the water pump replacement. While driving home in a snowstorm, of course). Also wouldn't hurt to replace the upper & lower hose and the thermostat all at the same time.

M52/54 water pumps fail pretty regularly in the 70-100k range. If you've made it to 100k and never replaced it, just do it, it'll leave you stranded soon enough (mine lasted all the way to 135k, but I'd rather have been able to choose the time of replacement instead of it choosing the time).

While you're at it, replace the expansion tank (I didn't heed my own advice and the tank ruptured 3 weeks after the water pump replacement. While driving home in a snowstorm, of course). Also wouldn't hurt to replace the upper & lower hose and the thermostat all at the same time.

Great advice! I am thinking of buying my wife a 2004 X5 with 58K miles. I am unsure if the PO did the WP, but I can always ask. But if they didn't, I can make it 75K, then install the WP, etc. What does the Shop Manual say?

Shop manuals don't generally offer replacement intervals for cooling system component other than hoses. Waterpumps are usually a "replace 'em when they fail" item. But armed with the knowledge of 75-100k normal lifespan of those components, I'd say if you make it to that range replace it when you have a spare afternoon sometime in that range.

Will do! Thanks Critter.