I noticed a horrible noise when I started my van on a recent trip. Something like a loud rumble. The noise always happens when the SAI pump comes on during a cold start although I believe I have heard it when running the van cold. Pump runs ok and isn't the source. Combi seems to be ok.
I tracked down the source and it appears to be coming from near the exhaust manifold. I can feel the rush of air but haven' taken apart all the bits to get a good look at it and it' tucked back behind the engine. It seems to be coming from the hole in the photo or another one near it. It's not coming from the exhaust header. If i cover it with my finger, the noise goes away and the engine idles normally.
At first I thought it was a bolt that fell out but this picture was taken a few years ago when I had the valve cover off. Is there a slug that might have fallen out here? Another orifice that may be the source of the leak?