I posted this under general discussion but I think this may be a better place.
I have an 04 F-150 with the 3V 5.4 Engine 166k Mi.. The vehicle is routinely driven on long trips and I have been noticing water mixed with oil under the filler cap and dipstick. There is no water in the oil in the oil pan and no coolant loss is apparent. I think the PCV valve may be stuck (if there is one) or some other issue with the crankcase ventilation. Any thoughts?

 

At the very least, I'd change the PCV. They're inexpensive and easy to change on some vehicles but hard to get to on others. Not sure on your vehicle.

 

on the 3v engines the pcv is built into the valve cover so you would have to replace the entire valve cover

moister on the underside of the cap is common on these trucks in cold climates

 

That's wild that the PCV is built into the valve cover. In all my years, I have never seen such! If it were me, I'd go to the local auto parts store and ask to buy a PCV for the vihicle. If they toss one up on the counter, I'd try my damdest to pull the original out and install the new one.

 

Thanks for the Info. When I get a chance (A warmer day) I'm going to pull the hose off where it looks like the PCV valve is (Drivers side valve covet) and see if it's gummed up and squirt a little carb cleaner on it to clean it up . I should be able to test it by putting a vacuum on it. If I need a lot of cleaner I'll change the oil. Strange thing is since i bought the truck 2 1/2 years ago with 37k on it (now at 166k) I've used synthetic oil with a 5k mile change interval.
but it was Supertek from Wal-Mart

 

Just give the parts place a call to ask if they sell a PCV valve. That will give you a clue and get you going in the right direction.

To clean the PCV, it needs to be cleaned on the inside. When it gets gummed up, the check ball cannot do the job. I have pulled them, filled them up with carb cleaner, shake the hell out of it (until the check ball is free - you can hear it clicking as it moves back and forth), then reinstall. That was when I was in the service and broke. Now, I just buy and install a new one. However, the cleaning works.

I'd have to see the PCV built into the valve cover to believe it.

I don't know who makes Wal Mart's Super Tech oils, but it must be manufactured to federal specs to be sold in the U. S. My money says it is way better than regular oils. 5,000 miles between changes on that oil seems fine to me.

Be sure to let us know if that PCV is indeed built into the valve cover.