Hi,
To make a long story short my 2000 328i (64,000) was low on coolant three times back in Dec-Jan, 04. On the third time I discovered some milkshake-creamy looking stuff in the radiator. Well, it turns out that I had a blown gasket & cracked cylinder head. After arguing with the unprofessional people at the extended warranty & seven weeks later I finally got my car repaired. Hope that's not your problem, but something to think about.
Dan462000.