BMW 750Li Repair Question
Loud humming noise.
You might check for an air plenum problem...
18,145 answers provided
so it might have a vacuum leak in the plenum? I'll definitely check that, but why would the noise be coming down by the torque convertor?
6 questions asked
could be the PCV valves on the back end of the plenum
(one on each side) it would make a sound like you described. to check this use a slack tube manometer at the crankcase, more than 6" of difference from side to side and that's where to start. repost if more help is needed
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