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Old 03-02-2012, 09:31 AM   #1
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Default Ccv/PVC and valve cover replacement?

I have a 1988 mj 4x4 4.0 and I'm getting a good bit of oil in the air box. From what I have researched the cause of it is either worn rings or ccv/PVC? I don't think it would be worn rings. Is doesn't really seem to burn any oil of through the exhaust. Also the engine only has 103,000. Anyway, the valve cover gasket is also leaking a tad bit so would like to go ahead and replace that also. I have been searching around for a good write up on doing this but have yet to come across a good one. What I would like to know is if I wanted to replace the ccv system entirely instead of just the PVC valve what does that al intell? How hard is it? What all parts will I need, and how much will it cost. Sorry if that's alot to ask in one post guys. Hope I can get some help with this.
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Old 03-02-2012, 10:31 AM   #2
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what's an mj?
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Old 03-02-2012, 10:33 AM   #3
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what's an mj?
MJ=Comanche
XJ=Cherokee
ZJ=Grand Cherokee
WJ=Grand Cherokee
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Old 03-02-2012, 10:38 AM   #4
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Originally Posted by kjc View Post
what's an mj?
seriously?

The front PCV valve is just a beather for crank case gases that get recirculated into the air box. You can remove the hose connecting it to the air box, cap the connector on the box and then buy one of those tiny cold air intakes and pop that on the front PCV valve. They only cost $10 at autozone. Be careful with the PCV valve when putting the filter on, they can be pretty brittle. The size isnt quite right so you'll have to twist and push.
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Old 03-02-2012, 10:40 AM   #5
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MJ=Comanche
XJ=Cherokee
ZJ=Grand Cherokee
WJ=Grand Cherokee
Thanks. Sorry I guess I should have said Comanche. The Comanche is basically identical mechanically and almost cosmetically as a xj except with the back half cut of and a truck bed put on a hybrid frame.
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Old 03-02-2012, 10:44 AM   #6
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seriously?

The front PCV valve is just a beather for crank case gases that get recirculated into the air box. You can remove the hose connecting it to the air box, cap the connector on the box and then buy one of those tiny cold air intakes and pop that on the front PCV valve. They only cost $10 at autozone. Be careful with the PCV valve when putting the filter on, they can be pretty brittle. The size isnt quite right so you'll have to twist and push.
I guess from what I read what causes the clog in the system and creates the blow by is some
Part of the ccv system that's on the back of the valve cover. I'm just trying to get more detail on it. Apperntly the old 4.0s don't have a pcv it is replaced by a ccv system. I'm trying to get more info if any of this is correct?
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Old 03-02-2012, 02:36 PM   #7
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Bump
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Old 03-02-2012, 03:11 PM   #8
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pull the rear line off and spray carb cleaner into the tube to clean it out watch for back spray in the eyes,the front tube should not be unhooked from the throttle body suction this removes crank case pressure when vacuum is not present such as accelration and high way speed excessive crank case pressure can cause gasket leakage and excessive blow by
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Old 03-02-2012, 03:16 PM   #9
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front tube is actually an "intake" for the valve cover. rear tube connects to the manifold. air flows like this in the renix system...

airbox - hose - front of valve cover - back of valve cover - intake

you should have a tiny bit of suction on the front hose with the engine running.
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You made me open up a service manual!!!
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Old 03-02-2012, 03:24 PM   #10
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front tube is actually an "intake" for the valve cover. rear tube connects to the manifold. air flows like this in the renix system...

airbox - hose - front of valve cover - back of valve cover - intake

you should have a tiny bit of suction on the front hose with the engine running.
correct until you touch the throttle then it draws thru front hose thru air box via throttle body
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Old 03-02-2012, 03:31 PM   #11
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Here is what you're looking for:

http://www.jeepforum.com/forum/f310/...ite-up-733669/
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Old 03-02-2012, 04:11 PM   #12
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Quote:
Originally Posted by freegdr View Post
correct until you touch the throttle then it draws thru front hose thru air box via throttle body
i dont think so... the vacuum increases as you increase the throttle. the vacuum in the manifold would still be greater than any vacuum located at that point on top of the filter, so it would still flow the same direction.
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Originally Posted by cruiser54

You made me open up a service manual!!!

Last edited by jakbob; 03-02-2012 at 04:13 PM. Reason: didnt want to sound like a douche.
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Old 03-02-2012, 04:19 PM   #13
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Quote:
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i dont think so... the vacuum increases as you increase the throttle. the vacuum in the manifold would still be greater than any vacuum located at that point on top of the filter, so it would still flow the same direction.
watch the gauge trhe second he throttles the motor more air is drawn in thru intake manifold than thru vacuum ports
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Old 03-02-2012, 04:22 PM   #14
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Quote:
Originally Posted by freegdr View Post
watch the gauge trhe second he throttles the motor more air is drawn in thru intake manifold than thru vacuum ports1985 Mustang GT vacuum gauge test - YouTube
youtube is blocked at my work :/
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You made me open up a service manual!!!
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Old 03-02-2012, 04:33 PM   #15
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Quote:
Originally Posted by freegdr View Post
watch the gauge trhe second he throttles the motor more air is drawn in thru intake manifold than thru vacuum ports1985 Mustang GT vacuum gauge test - YouTube
i got enough cell reception to watch... dont tell my boss...

right, but there is still vacuum. if there wasnt vacuum, why doesnt a vacuum leak whistle? and why isnt this filter (my pic) not covered in oil?

mind you, im not trying to come off as a dick. im trying to understand something my reasoning says is wrong (but if i am wrong, consider myself "learned" lol)
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Quote:
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You made me open up a service manual!!!
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Old 03-02-2012, 04:33 PM
 
 
 
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