What else would cause slight traces of 'lubricant' in my coolant?

[TimGinCentralNJ]

...just did my water pump 1 month ago (used BMW coolant w/ distilled water, although I did not flush the system) and noticed yesterday my coolant level was down about 1" from cold fill line. There was also a slight amount of 'goo' which resembled oil floating on top of my coolant. First thought to enter my head was to hang myself, the second thought being "oooh goody, a head gasket".

Why wouldn't I have any frothy coolant in my oil, a bad idle, white water vapor in my exhaust, or any of the other trademark signs of a head gasket? I'm also not losing any oil whatsoever.

My non-bimmer gearhead buddy told me not to freak out too much over the 'goo' one can find in the coolant resevoir sometimes, but in that I just dropped $1700+ with my indy for some front suspension work, maybe I'm being a little over-sensitive right now.

Is there any other way for engine oil (or any other lube) to end up in my coolant? At this point, would it make sense to do a leak-down test?

Thanks for your experience 'n wisdom,
Tim "a little short on both" Goodell
'91 535iM

[632 Regal]

that it might simply be some sort of coating applied inside the waterpump to protect it while sitting in storage (good thing).

Aside of that yes it is possible for oil to seep past a head gasket into the water passages without any other symptoms (bad thing).