Aluminum Head Cover oil cap

[228jeeper]

I repaired a leaky valve cover gasket and was still finding some oil in the driveway. When I replaced the valve cover gasket, I cleaned the valve cover as good as I could. Now it seems that there is oil coming from under the oil filler cap and onto the valve cover. It is the press in type, not threaded. The one closer to the firewall has the same problem, but it is a bit smaller. When you pull it off and look at the underside, in the center of the shaft that fits into the hole in the valve cover, the aluminum(?) is pushed in like poking a hole in the top of an aluminum can. Could this be my issue? Any suggestions would be appreciated. I will try to post pics later. Thanks.

 

[228jeeper]

OK, what I have determined I have is not an oil filler cap but rather two push in breathers with rubber grommets in the valve cover. I have attached a pic of the underside of the breather. It looks to be pried open. Should it be this way? Thanks.

 

[Old Dog]

If you have 2 breathers than you probaly don't have a working pcv system.
If this is the case you are building up cranlcase pressure and blowing the oil out.
If you don't have a working pcv valve you need to get one hooked up.
If you do have a pcv. than it's either bad, or the rubber grouments are not sealing where the breather goes in.

 

[228jeeper]

I do have two breathers with rubber grommets. Should I replace both of them and the grommets? And should I replace them with just a cap? I can replace the pcv valve (which I have one hooked up) while I am at it. Thanks.

 

[Sasquach]

Like the Old Dog said you need to correct your pcv system. One should go to the air cleaner and the other the pcv vacumm and it will create a loop in the crankcase ventalation.

 

[228jeeper]

Here are a couple of pics of my set up underhood as it was when I bought the jeep. Is this not how it should be? I have a pcv valve in the valve cover which has a hose running from it to a port below the aftermarket air cleaner. There is also a port above that that is not hooked to anything. I have replaced the pcv valve and grommet. Thaks for all of your help.

 

[Sasquach]

I am not familiar with how your 86 model should be plumbed but the pcv hose going to under the air filter needs to be looked at, I think it may need to go to manifold vacumm. Find a diagram for your specific year and see if helps.

 

[228jeeper]

OK, thanks I will check into it. But if it is connected in the wrong place, what are these two connections below the aftermarket air cleaner for?

 

[Rescue Diver]

I can't tell from the pics what your PCV hose plugs into?


Your PCV valve's hose should either plug directly into the intake manifold, or into a large vacuum port on the bottom rear of the carb, but I don't think your carb has one of those.

One other thing, your oil breather caps are the type that vent through a bunch of holes on the underneath side of the cap. You might want to replace one of them with an oil breather that vents through a tube so you can run a hose from it to the bottom of your air filter, and replace the other with a regular press in (Un Vented) rubber oil cap. That way you'll have one breather vented to the air filter and one PCV to draw out the blow by.

I wish I had a pic here at work of how mine is routed so I could attach it as an example. I know there are a few pics of my motor floating around this site in various threads. I'll see if I can find one of them.

 

[Rescue Diver]

I found a couple of the pics from old threads. This is my settup. My valve cover is for a stock aluminum 4.0, but the settup should be similar. I don't have the hose for the PCV hooked up in the pic, but it just runs behind the carb to a T in the hose for the poser brake booster that comes directly from the intake.

 

[228jeeper]

The PCV Valve hose is plugged into the top port of two in the front of the carb. There are three hoses at the rear of the carb. One is to the distributer, one is to the choke, and the other is plugged, see the attached pics. Is the plugged one where my pvc hose would need to go? My air filter housing has a tube coming out of the bottom of it that is also plugged. Am I correct that I could get a breather that vents through a tube for the rear of the valve cover and connect it to this port on the bottom of my air filter housing? Then I could get a press in rubber cap like you are talking about for the front of the valve cover, the oil filler hole? Thanks alot for your help.

 

[Rescue Diver]

The PCV Valve hose is plugged into the top port of two in the front of the carb. There are three hoses at the rear of the carb. One is to the distributer, one is to the choke, and the other is plugged, see the attached pics. Is the plugged one where my pvc hose would need to go? My air filter housing has a tube coming out of the bottom of it that is also plugged. Am I correct that I could get a breather that vents through a tube for the rear of the valve cover and connect it to this port on the bottom of my air filter housing? Then I could get a press in rubber cap like you are talking about for the front of the valve cover, the oil filler hole? Thanks alot for your help.

Yes, running a hose from an oil breather with the tube for a vent to the currently plugged tube on the bottom of your air filter would be a good idea.

As for where your PCV valve hose is connected, you really just need to make sure it's a large diameter, unported vaccum opening in either the carb or intake. These locations will vary with different carbs and intakes. If it's big, and you unplug it while it's idling, it should draw a whole lot of vacuum volume. Putting a rubber oil cap in the front hole of the valve cover would be fine. It really doesn't matter how you arrange things with the various holes. All you want to make sure of is that you have one hole with a good working PCV valve, one hole with a good breather(preferably vented to the air filter assembly if you don't want oil drips on your valve cover) and one hole that's plugged by a regular un vented oil cap.
And be sure your grommets are still soft and fit really tight against the PCV and breather. If not, go to O'Reilly's and buy new ones. They have a good assortment in the HELP section.