I have a 2004 BMW 545I that's running HOT and I'm losing alot of antifreeze.

Check for leaks in radiator, hoses, and look for coolant on the passenger side floor. If you find coolant on the floor, replace the heater core.

i have the same car with 64000 miles . and it had the same problem . they told me it was the water pump so i replaced it . but it didnt work . so the problem is that the seal bonded to the coolant pipe inside the engine fails.They say to fix the problem, it requires removal of the front of the engine and timing cover case. Then replace the coolant pipe. The only problem with that is it is not a solution, because you are using the same coolant pipe that BMW started with in the first place. It will fail again, not to mention the extraordinary expense, upwards of $5-6K and possible 5-7 day time frame. but theres a company in california which makes a custom designed specialty coolant pipe manufactured for this very problem. it wont b cheap but itll b way cheaper than if u go to a bmw shop .