I had a re-manufactured motor put into my 1999 a couple of years ago and noticed not long after it was losing oil. I took it in under warranty and it turned out to be the camshaft sync thingy leaking.
I figured that would have stopped it but it's still slowly losing oil, about a quart every thousand miles.
I don't drive it much so it hasn't been an emergency but it's something I'd like to solve.

The exhaust, as far as I can tell, is clear. I haven't seen any oil hanging around on the engine. It's like the oil is vanishing into another dimension or something.

I took it in to the shop again and the guy said it was probably the PCV valve, so he cleaned it, but it's still losing oil.

My dad-in-law also pointed to the PCV valve, and when I inspected the general vicinity of it, there was a fine sheen of oil around where it sticks out of the valve cover, so I decided to get a new one. This was my first exposure to PCV valves and they seem a pretty simple thing, a little metal slug in an open ended cylinder. Anyway the old one didn't show any signs of blockage or brokenness. It was coated in a fine layer of oil, so I went ahead and slipped the new one in.
There doesn't seem to be anything to hold or grab the valve, it just sort of sits loosely in the cover, which I'm not sure is right or not.
I did fire up the engine with it off. It idled rough as heck but I did verify there's very good suction on the hose that plugs into the top of the valve.

I was trying to find where the other end of that hose went, which has resulted in a whole other oops-broken-mystery-part mini-saga (https://www.ranger-forums.com/2-9l-3...0/#post2139159).
Oh well.

Anyway, do any of the long time Ranger guys here know other reasons why a new-ish 3.0 Vulcan would mysteriously lose oil slowly over time like this?

 

Welcome to the forum

PCV(positive crankcase ventilation) pulls dirty air from the crankcase and valve cover areas of an engine, and mixes it with intake's air to be burned in the cylinders.

On piston engines anytime a cylinder fires there will be "Blow-by", some of the expanding gases(exhaust), that push down the piston to give engine power, "blow-by" the pistons and rings and end up in the crankcase.
These gases are VERY hot, and the cylinder walls below the rings have a coating of oil to lubricate and cool.
Some of this oil is vaporized by the HOT Blow-by, and thats where oil vapor inside the engine comes from.
So there are blow-by gases and oil vapor in crankcase, valve cover areas are connected to crankcase via drain holes and other open passages.

Back in the 1960's there was just a open tube in the crankcase pointed down at the ground and the blow-by and oil vapor simply exited the crankcase and into the air, so pollution.

PCV system pulls that dirty air into the intake using engine vacuum.
The PCV Valve has a weight valve inside, high vacuum, i.e. idle, pulls the weight UP to close off the valve, it is still pulling in some dirty air, but at idle there is not much blow-by.
As RPMs increase vacuum gets lower and weighted valve opens more pulling in more dirty air, so it is a vacuum operated valve but in Reverse, high vacuum less flow low vacuum more flow.

Because it is a vacuum system the connections tend to hold themselves together, vs a positive pressure system that tends to push connections apart and needs to be clamped tightly at all connections.
So loose fit for PCV valve is OK but not to loose.

PCV system also has a Vent hose, it allows fresh FILTERED air to be pulled into the crankcase and valve cover areas, Vent hose, also called Breather hose, will run from valve cover(sometime oil fill tube) to air filter box or intakes air tube so it pulls in filtered air


Oil doesn't evaporate so it is going somewhere, some will be vaporized but unless it is a very cheap oil it won't be that much.
So it is leaking out.

Put a piece of cardboard down under engine area where you park at night, then check it after a few days for spots.

Also pull the sparks plugs at some point and check tips for blackness, it means a valve guide seal is leaking, and that cylinder is burning some oil.
Very Light brown tip is good combustion

 

Thanks Ron for the explanation.
I suspected that vacuum pressure is supposed to "plug" the PCV against the valve cover. There's a rubber ring on top of the cover I guess to aid sealing. I'll watch and see if more oil appears around the outside.

I've never seen any oil in the driveway beneath it, but I suppose it could be pooling on the engine somewhere, or getting burned off wherever it leaks maybe.

Interesting that you mentioned spark plugs. It had a couple of times where I took several seconds to start, much more than usual. In the past this was old plugs, so I pulled a plug and inspected it. They're not that old, got about two years on them, it looked to be normal wear, but wasn't black. It was brown. The startup troubles went away, I figured it was some bad gas maybe, so I quit fretting about the plugs. However, I got a good deal on some iridium plugs before the problem went away, I just decided to save them. So I guess when the temps cool off I'll just change out the plugs and inspect the old ones, since it could be a per-cylinder thing.

Thanks again for the info.
B.