Oil in Breather 4.0 HO

[YJGaddy]

Why would I be getting oil in the breather area of my 4.0? Engine is not smoking. I have changed the 90 on Valve cover a while back and it stopped for a while only to return.

 

[JPNinPA]

It is common. Place an o-ring around the ccv valve. Also he sure the breather tube on the intake is not blocked.

 

[Bounty__Hunter]

It's likely the CCV system working in reverse. The CCV (closed crankcase ventilation) system uses manifold vacuum to pull crankcase vapors from the valve cover to the intake manifold to be burned. This vacuum then pulls fresh air from the air box or air tube to the valve cover.

If the vacuum line from the intake manifold collapses or becomes clogged (common), there's no vacuum and crankcase pressure will push oil into the airbox. There's also an inline restricted orifice on the vacuum line that often clogs with carbon build up.

The 90 elbow on the valve cover is not a pcv valve like found on older engines, changing it does nothing.