The pump did get more noisy before it failed. After doing a really good pressure test I now found that the tailpiece that goes from the outlet to the block and has the small branch going to the rad or oil cooler is leaking at the branch. The branch is poorly electro-welded (not sure if that's the right term) in, and is leaking slightly (I might have been a bit hard on it pulling the hose when I changed the radiator) so I ordered a new one (over$200, but comes with the short piece of hose for the water pump) hoping that they might have improved the way it's made but it looks no better so I'm reinforcing the new one with JB weld before I change it.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)