Onan Lister LPW DNxM engine crackcase vacuum question

[Digger556]

I've looked through the TMs for the genset and the engines, but cant find an answer for this one.

How does the engine generate vacuum in the crankcase? Every diesel I've worked on has a very obvious crankcase vent line that terminates between the cylinder intakes (or turbo inlet) and the air filter, using the restriction of the filter to generate vacuum. However I dont see the path on the LPW engines. Is it cast into the cylinder head?

 

[Ray70]

If you pull off one of the valve covers you'll find a small tube near the corner ( where the small 1/2 round dimple sticks out of the valve cover's edge. ) this tube runs directly into the intake port creating a vacuum path to the crankcase.
It almost looks like an alignment dowel pin in the corner of the valve cover, but it's actually a vacuum tube.

 

[Digger556]

Thanks Ray!

I thought those were just dowels, like you said.