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Old 02-26-2013, 08:24 AM   #14
Registered User
Join Date: Feb 2013
Location: Connecticut
Posts: 52
My Ride: 2004 325 XI
I have a way of checking for vac leaks that has worked for me on 2 of my 325's, I take out the air filter box and MAF sensor,
Where the maf sensor attaches to that 3" rubber hose I stand to the side bend over and put my mouth to the 3" hose get a seal around my face and blow, you should be able to pressurize the system and listen for any leaks. if all is good you should be able to build up a pressure and hear no air leaks, I have found 2 bad vac lines to the fuel filter pressure regulator, torn intake boot, and cracked line to the valve cover.
You can hear the hissing right away if you have a problem, it helps if you have someone look and listen as you blow in and hold a slight pressure, It looks and sounds funny but it has worked great for me. no need for smoke testing.
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