Hello, I recently got a 1987 325i sedan and believed it had a blown head gasket. After replacing the head gasket I'm still getting COOLANT in the OIL. I believe the head or block or maybe both are cracked. My questions are, what are the differences between the pre/post 9/1987 engines? What is compatible with the pre-update block? Can I use the updated head and pistons on the older engine? Does the updated engine swap right in? I guess I need to know everything about this "update" as I cannot find pre-update engines.. My car is 03/1987 according to Mdecoder. Thanks, -D.
I had a head that was cracked once that was verrry difficult to diagnose - very fine crack, very difficult to see, and if memory serves (it's been a long time now) in part because it was underneath where a rocker arm mounts or something like that. Once the engine was warm, leaked substantially - engine cooled off, the crack in the head would close, and made it much harder to find. In any case, do everything including cleaning the head to the nines to make any cracks easier to see before resorting to a full rebuild. Our resident tech may have an answer on the block, as far as I know the M20B25 blocks are all the same. I believe there are casting differences between the 'eta' M20B27 blocks and M20B25 blocks that precludes using M20B27 cranks/pistons/internals, etc. without machining. I'm reasonably sure cyl. head problems with cracking & warping are more common than problems arising with the bottom end - typically. Wouldn't be surprised if you end up finding it's a cracked head, of course you never know until you've solved the mystery & confirmed the problem. Also as far as I know, any 'i' "885" head would be interchangeable with any other on any M20B25 block. https://en.wikipedia.org/wiki/BMW_M20
