frank5079

I have a '95 F150 with a 300 six and 5 speed gearbox; could a faulty PCV valve cause some oil to travel down the vent hose into my airbox?

mustangGT90210

It most certainly could. My PCV valve went bad on my 5.0 and it caused all the blow by oil to go straight into the intake. My valve was hung open so it was just letting the crank case pressure go back into the intake, which carried some oil with it. To the tune of like a quart a week lol

Replace the valve, it's like $6 and it takes 2 minutes on a 300 after you find where it is. If I remember from my old truck, it's near the back of the valve cover

Chris_1

iTrader: (1)

Motorcraft only for that valve.

frank5079

Well I've replaced the PCV valve, the crankcase filter, and the engine air filter; I even cleaned out the airbox and the crankcase hose. I start up the engine and I've got good vacuum coming from the PCV. So I take the truck for a quick spin into town and I still have oil running from the crankcase hose, coming out the crankcase filter and puddling down the bottom of the airbox....what gives???

gdwinfield

You might have worn rings

sdmartin65

The Ford 4.9 and Jeep 4.0 inline motors are prone to blowby as they age. Simple solution to keep oil out of the air box is to get a 96 intake system from the wrecking yard or modify what is existing.

frank5079

So by doing this, I am basically I'm rerouting the crankcase hose from the airbox to the front intake tube thereby letting the oil get ingested by the engine through the throttle body...

sdmartin65

Yes.

I had a 95 with bad blow by and attached the existing breather hose to the top of the air box. No more oil from air box on the driveway.

Chris_1

iTrader: (1)

Pretty much exactly that. Which is not really solving anything, other than putting the oil mess where you can't see it.
That hose is actually supposed to be an inlet hose and the PCV valve and hose at the other end pulls it out after it's been pulled all the way through the rocker/lifter/crankcase area, theoretically. That's supposed to create negative pressure in the oil galley areas etc so pressure doesn't build up and push oil out to all the places it doesn't belong.
You could have too much pressure building up for the system to relieve (it would appear you do). This can be caused by excess blowby from worn out rings. It can however also be caused by blockages in the system.
Blockages can consist of things like a plugged PCV valve or hose (I know you changed yours) but internally the air has to flow unrestricted as well. Sludge buildup inside the oil gallery system can start to block holes and restrict that flow.
Sometimes running a few oil changes with an engine cleaner like Seafoam will clean up the sludge and get the system working better.
You may still have an issue if you have excess blowby, but getting everything in the PCV system working at maximum efficiency might help with the problem. It certainly can't hurt.

frank5079

Thanks guys...guess I'll try both suggestions. At least I have a gravel driveway so I don't have to worry about oil spots.