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samlmoore 8/9/2012

2004 BMW 745i Base 8 Cyl 4.40L


When I start my car from a cold state it makes a vacuum sound for about 45 sec then go away. When I stop at the stop li

Car has 104000. Codes are PO491 and PO492

1 Answer


HouseCallAuto 8/9/2012

You have a air injection air supply hose under intake manifold that is broken and leaking and this is your noise that you hear and this is the two codes you are getting. the secondary air pump puts out air pressure that is escaping from the broken air supply hose. The intake manifold has to come off and the part is a dealer only part.


HouseCallAuto 8/9/2012

The reason you only hear it for 45 seconds is because the asir pump only runs for 45 seconds after startup cold and then the pump shuts off. Imagine the sound if you were vacuuming your house and someone were to remove the hose out of the front of your vacuum. The sound would chasnge dramatically.

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