PCV question

[Aaron]

Tomarrow I was planning to mess with the choke system on my 86 GW (Thanks everyone who responded) and also do my rear seal. I just bought the GW a couple weeks ago, and it leaks a TON of oil. I did the valve covers and it made no difference, and I also replaced the PCV valve thinking it was clogged up. I thought it might be clogged up because there was a good bit of oil in the air filter housing.
Well today I drove the GW to the car wash to clean the oil pan. After I cleaned it, I left the oil fill cap off thinking that the leak might still be due to something in the PCV system. Well when I got home, and let the Jeep sit for a few minutes, I was pleasently surprised to find that it leaked only a half dollar sized spot rather then a 4 inch diameter circle. I then took the filter out of the oil fill cap (It was REALLY clogged up) and put the cap back on but left the hose to the air cleaner disconnected.
I guess I'll see when I get home from work if the leak is better. I can live with a small leak, but it was getting rediculus (2 quarts/per tank of gas)

After all this ranting, my question is....
Does anything upstream or downstream of the PCV valve ever clog up?

I'm keeping my fingers crossed that I can get by a bit longer without doing the rear seal. I'd rather play around with the carb then mess with that seal.

[porchpiggy]

Your PCV should not be hooked to your air cleaner. It should run into the carb. The hose that goes to your air cleaner is to supply clean air to the crank case. The oil in your air cleaner is from blow by, caused by worn rings and/or valve guides. When your engine is running, check your oil fill tube. If it is sucking in air, life is great. If it is blowing out smoke, you have a case of dreaded blow by. The pcv can sometimes be blocked by cooked oil at the manifold, inside the opening. Apply vacuum to the end that goes into the carb base and see if you have free flow. Blow by and a non functioning PCV system will produce a lot of oil being pushed out every seal/gasket.

[DjD]

I have the same problem. I blew through a 3' hose that I connected to the metal tube that comes out of the crankcase (where the PCV valve connects to the crankcase) to make sure that tube wasn't blocked. Ended up buying a new 710 cap from the Stealer, only $10, which brought the oil leak spot down to the half-dollar size. The vacuum diagrams show the direction of PCV air flows: air cleaner->oil filler tube->crankcase->PCV valve->base of carb/intake. But the Haynes manual says "if abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to flow back through the crankcase vent tube (oil filler cap) into the air cleaner to be consumed by normal combustion."
You should re-connect the hose between the air cleaner and oil cap or else you're going to have oil all over the engine. Actually, buy a new piece of hose, oil is probably dripping out of the loose ends anyway, I think it's 1/2". Having a filter in the cap will keep most of the oil in your crankcase and out of the air cleaner (I'm hoping). I think I read somewhere hear that they make an aftermarket cap to replace ours, maybe it's cheaper than $10.

[Aaron]

Porch Piggy- PCV isn't hooked to air cleaner, but removing oil fill cap seems to vent engine better.
Why would crankcase ever suck air in? There should always be some combustion gases that get by rings and or valve seals.

DjD- I need a new cap too. $10 isn't terrible. I don't think you can buy JUST the filter that is inside it. Mine was TOTALLY jammed up with carbon and such. I thought it would spit oil out too without the hose hooked up but so far so good. I'm gonna do like you said and blow through the tube connected to the PCV valve. I bet its clogged. That would be great. Hell a half dollar sized leak is just like automatic rust-proofing :0)

[DjD]

The crankcase doesn't suck air, the sucking starts at the intake/base of carb, then the air is just sucked through the crankcase from the oil cap/air cleaner.

If it doesn't spit any oil, how else did the cap get jammed up and oil get into the air cleaner? I think with so much blow-by, the intake doesn't do enough sucking, so the excess pressure from the blow-by exits out the oil fill tube.

I'm hoping my new oil cap will reduce the amount of oil that ends up in the air cleaner, haven't checked it yet, but I'm sure going to keep that oil cap filter clean. Otherwise, "check the gas and fill the oil."

[johnwom]

I had a similar problem with my Chief.

After I had the engine rebuilt I noticed oil seemed to be leaking everywhere and the rate of oil consumption was about a quart per tank of gas. I had oil in the air cleaner too, more than I felt should be there. I had the oil pan gasket replaced, no success.

I think I fixed it by accident. On a whim I bought a chrome breather cap to go on my oil fill tube. No more oil on the enigine, and no more adding a quart per tank. Obviously there's no more oil in the cleaner since the chrome cap eliminates the connection to the air cleaner.

I have no idea why it worked but it did.

John

[Aaron]

Well, letting the oil fill cap breathe fixed the problem. I drove about 250 miles over the weekend, and the truck went from leaking 2 quarts in 100 miles to leaking around 1/3 quart in 250 miles. I'm a very happy camper indeed!

Also found a hitch for the beast at the junkyard. $10 for a class III, can't beat that!

[johnwaynejeep]

Thanks Porch Piggy, great info on blw by. Blow by was always a problem with my rig. Now I can easier diagnos the problem with my next rig.