So I've got oil blow by at my from CCV grommet and my oil fill cap. I recently pulled the valve cover off thoroughly cleaned it replaced both grommets and oil cap and I'm starting to see small amount of oil push up passed the oil cap and around the seating of the front grommet. I also did the MOD on the valve cover where I cut off and drilled the stems inside valve cover. Any ideas what would cause this issue?????

 

Have you done a compression test?

It is most likely blowby from worn rings causing excessive pressure in the crankcase. My 2.5L is suffering from the same problem. I ended up having to silicone the fill cap shut and use the PCV opening to fill the oil because I could not stop the oil from coming out at the fill cap. It is working until I can put in new rings though.

 

Year/engine? Always include when starting a thread as there are significant differences through the years.

Compression test always a good idea here as a starting diagnostic test.

 

1990 4.0 I6.

 

How many miles?

 

204,000

 

Excessive piston ring gap.

 

Very likely. You must start with a compression test. Dry, then wet if readings are low. SEARCH for information on "how-to" on this test.

The compression spec for the 4.0 is 120-150 psi, with not more than a 30 psi variation between cylinders.

Post back with test results.

 

Did you bend up the sheet metal tangs below the grommets?

Aware of the updated tube/orifice from valve cover to intake manifold?

 

Besides the above, the front 1/2" tube needs to be free to vent. If it has a little aftermarket filter that's all gummed up inside, or somehow a kink or restriction in a line off there, crankcase pressure will try to blow oil out anywhere. Rear main seal even.