For the past several weeks I've been hearing a "hissing" sound from my engine. First thing I did was check the plugs to make sure they were all tight. That checked out. Then I checked all vacuum hook ups, all good there. Made sure the intake was all bolted up tight, check. I'm running out of ideas, and it may be that I'm just paranoid. Take a listen to this video I took late last night. Now, its dark, I took the vid for the sound, not the picture. It's kind of hard to hear over the KB, and of course the efan kicks on. Seems to be coming from the left side (passenger), or the front.

http://fast-trucks.com/Motor_Noise.mpg
MPEG2 Format

 

I tried to load it but it came up 'broken'? Can't think of anything you havn't checked but the exhaust manifold, pipe, ???

Dan

 

I've got long tubes, I guess it could be a leak from them. I'll check it out.