Strange air leak in ignition cavity

[d2w]

This may be a case of "If it hurts, don't do it!"

I have a '06 EC300. I've modified the ignition cover so that the drain (fill ) hole on the bottom is plugged and there's a hose nipple on the top. A hose is connected from the nipple and is routed up in behind the rads.

As a test, I blew into the hose and I could hear air hissing out somewhere in the vacinity of the spark plug, head, or exhaust port. Would you expect that? I would have thought the ignition cavity would be sealed off from the engine crankcase. Or perhaps the seal is designed to only work with the crank at a higher pressure than the ignition cavity? But doesn't the crank cavity pressure go negative during the intake stroke?

I need to more precisely identify where/if I'm hearing a leak. But I sure would appreciate it if someone could say "Ya, that's normal".

And I'm experiencing no engine problems, or oil in the ignition cavity, etc.

Again, perhaps I simply shouldn't be blowing into the ignition cavity.

Thanks

Dale

[iancp5]

Hmm you'd hope there wasn't a path from ignition case to head? After all you need the crankcase reasonably well sealed but ... if you're pumping air in at high pressure maybe you'd expect a slight leak as maybe the seals will pass some air in the wrong direction. If have enough pressure somethings going to give eventually. You sure it's not poor hearing though?

[GMP]

Perhaps through the wiring harness sheath, where it ends near the head under the tank?

[MattR]

+1 on the wiring harness sheath.

[d2w]

What a Homer (Simpson) I am.

The wiring harness was the source. I guess if I had just used my brain rather than my typing fingers I would have solved the problem hours ago.

Thanks to Glenn and Matt for their knowledgable responses. Your Super Moderator status are deserved.

Dale