I have 130,000 miles on my 07 550i. I get an occasional spot or line of coolant in my driveway. Very small amounts. So I looked around the water pump and front block weep hole, nothing. I pulled the lower covers last night and see evidence of long term slow leak at rear of engine running down the back of the block and out the passages where the block and bellhousing meet.

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Found this video https://www.youtube.com/watch?v=F_gjFZJbAoE
Great video, seems right on point, but it points to either the rear coolant passage cover 5 or the valley cover 1 or both. He says to pressure test the system, but with as inaccessible as the two are, I don't see how you can localize either leak without having the tranny off or the intake off. So, it doesn't seem to be the ubiquitous transfer tube, but looks like a ton of work either way, top end or back of block. Anyone do one or both of these?
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