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The Case of the Missing PCV Valve! Or is it?


 
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artdplmr
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Joined: 08 Jun 2006

PostPosted: Sat Oct 14, 2006 11:13 pm    Post subject: The Case of the Missing PCV Valve! Or is it? Reply with quote

Help!- My 1988 Cherokee i.l. 6 is blowing a qt of oil a week into the air filter case. I'm buying air filters 3 at a time, changing them every other day. I Read the tech posts, and replaced the vacuum hoses, checked and cleaned the grommet and hose. Didn't help. Pulled the valve cover, cleaned the carbon and sludge off the inside, snorkels, and splash guards. But I didn't see any sign of a pcv valve. I thought it was integral to the valve cover, inside there somewhere, but I don't have one inside my valve cover. And it's still blowing like a white house intern!

Is there supposed to be one (a pcv valve) in there someplace, and mines gone? Is there a chance the p.o. removed the pcv valve in some crazy self-repair hypno-trance? I did inherit the blowby from the p.o.

Has anyone tried retro-fitting an inline style pcv valve from a different application? I mean that hose is right there begging to be experimented with.

Blowby comes from worn pistons/rings usually, right? Doe's any of that additive stuff like "Restore" help with that? I know, I know, but I had to ask.

Any advice and/or help would be greatly appreciated!! I just don't want to spend $280 for a new valve cover if it's not going to help.

Thanks and keep Jeepin'!!!!!!
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Kingfish
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Joined: 06 Feb 2006
Location: Middle Tennessee

PostPosted: Wed Oct 18, 2006 12:16 pm    Post subject: Reply with quote

There is no actual PCV valve on the 4.0. There is a grommet with a specific sized opening (orifice) on the back side of the valve cover that goes to the manifold. If that is blocked it would allow a lot of oil to enter the air box from the front tube. Of course you may have a bigger issue with the engine if everything on top is where it should be. You could run a "catch can" as a temporary fix-you would run the hose from the valve cover to the airbox into some sort of can that you could empty for later recycling.

Here is a ling to the hoses I am talking about.

http://www.off-road.com/jeep/cherokee/xjtech/engine/40ltr/blowby.htm
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88WOWJ
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Joined: 12 Aug 2006
Location: Hinesville Ga

PostPosted: Wed Oct 18, 2006 5:00 pm    Post subject: Missing PCV Reply with quote

Not knowing your mileage you could need an engine. My 1988 engine was
puking a quart to two quarts every 36 miles. End result was a new engine
at 225,000 miles. My blowby problem started at about 130,000 miles.
I have talked to several mechanics (strictly Jeep mechanics).
As the link states in the previous post replacing the valve is the most
extreme other than the engine. Inside the valve cover are two
posts where the air and vacuum enter or depart. The 1988 did not have
a 3/8 hole drilled in the post. The 1991 did. The hole is supposed to reduce the volume of air inside the valve cover. I did this on my original
engine and in fact it helped. When I replaced my original engine I located
a 1991 valve cover and installed the 1991 tubes for that year. Trashed
the 1988 tubes , to expensive to replace. Going back to the valve cover
remove the three screws and remove the lower half of the tube from the
valve cover. Inside is a tin flapper that can gum up and not allow the air thru.Hope this helped.
_________________
1988 Wagoneer Limited XJ Tellico Tested
Rocklizards panels, Tomken rear bumper and front Tow brackets, Rocket air intake, 2 inch lift,
30x950x15, 1991 coolant system with electric fans, 8,000 mile marker winch
1991 Cherokee Limited
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artdplmr
Member


Joined: 08 Jun 2006

PostPosted: Thu Oct 19, 2006 8:31 am    Post subject: Thanks Reply with quote

Thanks for the info..That's kind of what I thought, that the motor is probably just shot. I had already pulled the cover and cleaned the snorkels and splash plates, and it really didn't help much. Thanks again guys!!
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