Why does the front PCV valve always have oil around it? I have replaced the gasket? There are no hoses connected to the front PCV and according to my friend he says that there is no oil that goes through there, but the liquid that is leaking out from it is oil?

 

Mine weeps around the PCV valve really badly, too. I figured it was just an age + blowby thing.

 

Let's first make sure you understand the purpose of the PCV valve and how it works.

PCV stand for "Positive Crankcase Ventilation". Its purpose is to maintain a constant flow of air though the crank case to remove combustable gases that accumulate from blow by on your pistion rings.

It does this by connecting a vacuum source to one of the valve covers, this is where the PCV valve is located. From the PCV valve you will have a hose connecting to the base of the carb. The hose now draws air, via vacuum, though the valve. As it draws a suction on one of your valve covers, it then draws air through the head (via the oil drain holes) to the crank case. Since it's drawing air from the crank case, it as to get air into the crank case from somewhere. It gets it from the OTHER valve cover. So on your other valve cover, you will have a breather, it is not another PCV valve. So now you have air drawn in through your breather, in one valve cover, through the crank case, up through the other valve cover, through the PCV valve and then sucked into the intake. Now have a constant flow of fresh air though your crank case getting sucked into the engine.

In this process, you will get oil vapors naturally sucked into the PCV valve and the intake. This is why it gets sucked into the common plenum of the intake, and not a single runner, this ensure the oil gets burned off by all the cylinders and not just one loaded up.

So you say your front PCV, you only have one. So are you acutally referring to the breather? If so, yes...there is no hose connected to that one. If that is the one that has oil leaking out, then it is possible that your PCV is clogged and stuck and not sucking any air, allowing pressure to build up in the crank case and blow out the breather.

With your engine running, remove the PCV from the grommet. You should be able to put your finger on the bottom and feel a suction, should be able to hear it as well. You should also be able to shake it and hear a rattle. This is a ball in there that acts as a check valve. If you don't have any air sucking into the PCV, then it needs to be replaced...they are $3 or $4.

It is also possible that your engine is getting old and has a lot of blow by and it's simply overwhelming the suction of the PCV and pressure is still building up.

Keep in mind that both the PCV and breather are mounted in the valve covers and there is a lot of oil flinging around in there. So it is also possible that you simply need a new grommet if it is not sealing correctly. If the oil is just leaking from around this grommet then replace it. If it's actually leaking from out of the breather filter, then you may not be getting a good ventilation....replace PCV and see if that helps. If you are getting oil out the breather, replace that as well. You probably will have it plugged up by now.

Sorry for the short story...hope it helps!!! Let us know what you find.

 

To add to what 82f100460 said, the check valve you should hear rattling when you shake it is weighted specifically for each engine. That's why there's a "wall" of them at the parts stores. If you install the wrong one, the system may not work correctly.

When I first built my 460, I just grabbed one of the correct size, not thinking about anything else. Installed it and ran the engine. I had oil blowing out of the dipstick tube, and bad. Went back and got one for a 460 motor and solved the problem.

A cheap part that's easy to replace for piece of mind.

 

I also want to add one thing. If everything on your engine is stock, then your "breather filter" could actually be mounted in your air filter housing and not directly on the valve cover itself. If this is the case, then you will indeed have a hose going from the valve cover to the air filter housing...to the filter.

 

If there aren't any hoses connected to the PCV valve and you are sick of the oil on the top of the engine, just run a hose from the valve down below the engine. In stock form, as stated above, there should be a filter in the air cleaner assembly hooked to the PCV. I've always hated dumping crankcase gases back into the intake, depending on the emission laws in your area this may be the ticket. Will also eliminate oil burning on the headers. I had a 86 with 220K on a 351W that blew oil like crazy from the crankcase, ran a tube to the frame and had a nice free undercoating applied every time I drove... (not exactly the most environmentally friendly solution)

 

Are you saying to eliminate the PCV system all together? The only way to evacuate the crank case is to force air through there, this is done by sucking it out via vacuum.

Simply hanging a hose off the valve cover to "Vent" the system does not suffice and is a recipe for a disaster!!! This has nothing to do with emisions...it has everything to do with evacuating comustable gases from the crank case. Have you ever seen a crank case explosion? This is a good way to have one!!

 

It's been so long since I've worked on that 86 that I totally forgot the PCV runs off vac while the breather came off the oil cap. Been working on oil burners too long... Correction, the breather off the oil cap is where the tube I'm speaking of went. Once the blowby was too much to be evacuated by the vacuum of the PCV system, vapor started blowing out of there. You should have seen how bad that engine leaked! Anyway, unless you are driving the **** out of your extremely tired gasser, don't listen to me, i'm an idiot ...

 

Kevin - I still can't rep you, but you deserve it for that explanation on the PCV system. Were you a lawyer in a former life? Paid by the word? I may lose my title as being the king of verbose.

Anyway, well done.

 

Hey man...wasn't trying to stomp on you. Just wanted to make sure the OP kept it safe ya know . Not an idiot, everybody has their experience right??

Thank You, Gary!!! Always a huge compliment coming from you

 

There is no danger of an explosion, all the old engines used a road draft breather system with no PCV valve. It was usually a hard line running out of the crankcase(with some sort of oil separator incorporated also) and it ran down below the engine where air passed by the opening, creating a little bit of suction as you ran down the road. Then they usually had the intake for the system up on top of the engine somewhere with another oil separation device(usually looks like steel wool).

It didn't work as well as a PCV system, and of course it dumped these nasty gases and water vapor to the atmosphere. Diesels kept using this system longer, because they have no vacuum in the manifold to make the system work. But they now use different derivatives of the system using the air intake.

And I have done the same thing as one other poster mentioned. If you engine is really shot, the gases from the engine will overwhelm the system and start putting a lot of oil in the aircleaner, making it run worse than ever. I have also kept the valve working, but take the fresh air pipe out of the aircleaner and tie to the frame to keep it going. We have had a couple of motorcycle guys chime in and say it would be a good idea to have a catch can down there on the end of the hose, and I do not think that would be much trouble to add, to keep the oil off the roadway.

 

On the old Harley's, the crankcase has a breather hose on it that points straight down to the ground. When you cut the bike off, she marks her spot every time.

So yeah, if you wanted your concrete to stay nice and white, you could forget it.

 

Was watching an episode of Horsepower Television the other day were they were building a 360 for an old Javelin. When they were on the dyno, they were blowing oil all out the PCV valve, were sucking up so much oil it was blowing smoke.

Turned out they were using an aftermarket valve cover that did not have a PCV baffle in it...so the PCV was sucking straight oil right off the rocker arms.

Made me think of this thread...makes sense, you want to be sucking vapors, not oil.

Something for you to check as well!! Summit, and probably other places, sells valve cover baffle kits if this happens to be your problem.