I have something strange going on with the PCV system on the 6.8L V10 in my F-53 chassis motorhome.

On my rig, the right valve cover is connected to the intake tract just forward of the throttle body (which would be the "intake" side of the PCV system) and the left valve cover (with integrated PCV valve) is connected to the intake manifold (the "output" side of the PCV system).

I'm seeing oily residue inside the intake tract coming from the right side valve cover. Since this is the fresh air intake side of the PCV system I'm kinda stumped. The manifold side of the PCV system is totally clean.

I started poking around because I'll occasionally get pinging under heavy load at or near full throttle. It happens randomly and goes away if I let up on the throttle. If I immediately go back to WOT the pinging doesn't return.

Looking at the reside I'm wondering of oil coming into the engine with the air might be the cause. Either way, I'm trying to figure out why I'm seeing oil on the non-vacuum side of the PCV system. I'm pretty tempted at this point to remove the hose, cap the intake tract side and put a breather on the valve cover to see what happens.

Any thoughts?

Thanks!

 

Something of a wag here. After shut down, it is possible that fumes are moving up the clean air side of that tube, since afaik there is no valve or one-way in the supply side. You could pull that hose off when the engine has just been run and see if you get a cloud.

 

Are you using synthetic oil?

Does the PCV valve rattle if you shake it? And is the hose/elbows going from the PCV to the throttle body not leaking?

 

under load or full throttle the intake will have no or little vacuum so the PCV closes. The crankcase will build a little pressure and is drifting a little oil into the intake. You can put a catch can there if you wish to trap it but putting a breather will make it worse since the pcv air needs to be metered. If you don't have a tune I suspect it's running a little lean up there, if can an data log it and watch the short term fuel trims. Lazy 02 sensor can be an issue as well.