Old thread, but just to add another data point on water pump failure:

Just had the water pump on our 2007 E70 go out at about 84,000 miles. Wife got it home, but the fan was making loud noises continuously. The dealer is only about 2.5 miles away, so I drove it over cold, coolants temps climbed to about 220 F just at the very last block, but that's just a bit over normal.

$1600 to replace the water pump, another $450 to also do the thermostat at the same time! Ouch! But now fixed and running steady at about 205-210 F.