I'm having this problem as well, but I was told by an independent repair shop that BMW does not have a new repair kit for the '01 X5 4.4 engine. That doesn't seem to jive with what was said above.

I'd put that heater on if it were available so the next guy who owns this car doesn't have this problem. I am DEFINITELY selling it as soon as it's fixed. I hope there is a buyer out there. I've looked on autotrader and yahoo autos and if I sell it for $14,500 I should be one of the lower priced X's on the market.