loud noise on 1998 BMW 740i

loud humming noise @ TOP right side of motor. noise seem to receed @30plus mph. yet @idle noise persistant. changed both belts and tesioner

by in Tacoma, WA on March 09, 2011
3 answers
ANSWER by on March 09, 2011
Check for vacuum leak. I could be grasping but don't skip basics.
ANSWER by on March 10, 2011
Are you sure it's coming from the front? Failed vent valve could cause this sound, but it's in the back of the intake manifold. If there is excessive amount of oil in the intake manifold the vent valve failed. If it's coming from the front all the pulleys has to be checked for worn bearings. Zee
ANSWER by on March 10, 2011
while the engine is running carefully and slowly loosen the oil cap and lift it SLIGHTLY off the valve cover- if the noise goes away it may be a vacuum leak. Be careful- oil will spray out if you lift the cap up too far!!
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