1995 F250 7.5l 4-speed auto.

Towing a 6500 lb 5th wheel camper last weekend at 55 mph I suddenly started leaving a smoke screen behind me. Found oil burning off of drivers side exhaust manifold. Topped off the oil and brought it home.

This week I swapped the drivers side valve cover gasket. It isn't the old style cork/rubber so I don't think that was the issue. A little RTV when I put it back on though just to be sure. Around the block a few times and the only thing I saw was residual oil from the leak.

Today I hooked the camper up to run up the highway a bit before planning another trip. Horrible smoke screen. Came home and found oil all over the exhaust manifold. Now to me it looks like the oil is coming form the base of the oil filler tower where the oil fill cap is on top of.

Pulled the PCV valve. Someone before me has drilled it out. So the valve is NOT a restriction, but I don't know if that is bad or not.

Tomorrow I'll test the vacuum to the PCV valve and with the truck running see if there is excessive pressure at the fill cap.

The truck DOES have 225,000 miles but up until this point it has run like a CHAMP, never burnt or lost any oil. I just upgraded the camper this year from a 4000 lb bumper pull to the 6500 lb 5th. I pull a 3000 lb boat behind the camper. No way I can pull both at this time.

Anything else I can test?

 

How did it look under that valve cover? Sludge and carbon build-up? How much oil did it take to maintain the level? If you are leaking oil onto the exhaust it will smoke-out the county. Clogged crankcase ventilation could make leaks worse. A catalytic converter hides smoke from oil consumption.

A leak-down test will tell you the most about the condition of your engine.

https://mobiloil.com/en/article/car-...-leakdown-test

We've had threads in the past that attributed enormous oil consumption in 460s to valve guide seals and leaks into the intake manifold. But not a smoke-screen?

The crankcase has to breath. Open passages from the air filter to the crankcase and from the crankcase to the intake must be maintained.

You mentioned the test tomorrow: When the engine is warmed up you can pull the oil cap and run the engine to see if it blows a lot of pressure out of the hole.

After a trustworthy leak-down test you know what you have to work with. If you're "billowing clouds of smoke" you might be past the external fixes and you need to know.

You could search and ask over at 460ford.com. Professional engine builders check in over there.

 

During high vacuum at idle, the PCV is supposed to be [mostly] closed to reduce air movement.

Even though the drilled out PCV would inhibit crankcase pressure build up (and the blowing out of gaskets because of it) it could cause other drivability or performance issues and maybe even oil in your upper intake manifold.

A lot of vacuum gauges also register low pressure psi.
Perhaps measuring the air at the breather hose at the air intake box could shed some light on it?

 

I recently started having smoke at idle. There's vacuum at the oil fill. I knew I had a leaky injector and bad valve cover gaskets, but after swapping them out the idle smoke continued. I've run a PCV oil trap in the past, so I put that back on as a diagnostic, and it is filling more quickly than I recall (that's when the smoke starts). I believe my PCV valve is stuck open.. You could put a trap on your PCV system, and see if that's filling up quick. Or simply change the PCV valve and see where you're at. There should be vacuum at the oil fill at idle, definitely not pressure.

 

Test the crankcase pressure with and without a functioning PCV. It might make a big difference.

Repeating myself: The vent from the air filter to the crankcase must allow free flowing air.

When you are towing a load the engine is working a lot harder. It might just be sucking the oil out. Wishful thinking.

 

Just put a powerstroke sticker on the truck, everyone will just think it's normal.

Above suggestions are solid, and a pcv that has been drilled out will undoubtedly pull more oil into the intake...especially at low load high vacuum scenarios.

With bad blowby, I'd expect to find oil in the air filter box as well

 

Why do you feel the need to repeat yourself. Nobody is contradicting you.

The function of a properly operating PCV is to reduce air flow during high vacuum by allowing the vacuum to meter the valve. Not entirely closed - but a reduction of available vacuum.
A properly functioning PCV will have vacuum and airflow at all times and having positive pressure at oil fill will be a problem for sure.

In an ideal world, the vacuum at the PCV would never be enough to suck oil out,
but yes,
pressure in crankcase means bad crankcase venting and/or a sizable amount of blow by.

 

I'll pick up a new PCV also.

PCV is on passenger side and oil is leaking from drivers side. Oil isn't being sucked through the intake as far as I can tell, just (excessive blow by?) (inadequate ventilation?) causing oil leakage around the oil filler cap.

I'll have more info after work.

EDIT: One more answer, engine is clean inside (225,000 miles clean). No sludge or buildup under the valve cover.

 

Nothing to do with anyone else. I tend to ramble and when I read my posts later I wonder if anyone bothers to read them. Kinda: if you don't read anything else ...

 

Line to PCV has FULL MANIFOLD vacuum at idle. (I pulled the line off the PCV and put my thumb over the line - great vaccum)

Hooked PCV line back up. Removed oil filler cap and line to air breather. Plugged line that was pulled from air breather and placed palm over oil cap. GREAT vacuum. Like FWOMP and it pulls my palm to it. Yeah, real scientific.

I did not test crankcase pressure with the PCV unhooked. Guess I'll do that next. Also I should verify the line from the valve cover to the air box is clear and the inside of the airbox isn't plugged somehow.

I'm leaning towards something cracked / loose where the oil filler cap tower thingy is factory attached to the valve cover. I'll pull the vc back off and inspect.

 

Two separate measures for those lines, pressure and volume. It can mostly plugged and still feel full pressure. When you start making lots of power and blowing more air they have to handle the extra volume.

I hope you post back with anything you find. My 460 always used more oil than I would like. Someday I might try to find out why. Mine never showed smoke until the last couple years. I let someone use it for a while and it was never quite the same afterward. Now if you romp on it at low speed it smokes out the exhaust.

I've always thought that valve guide seals, intake gaskets and new crankcase breather lines would be a start for mine. Compression check is good but I never did a leak-down test. Leak-down test would be first.