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  #11  
Old 08-13-2008, 10:06 PM
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Quote:
Originally Posted by Jim_Lou View Post
Glad the carrier worked. I hope this problem is as simple.
Well I pulled the PCV valve out of the grommet and cable tied it out of the way and drove it several miles and got just a little seepage, not even enough to drip onto the drive! I may try to find an old style breather that will fit into the valve cover somewhere and say to hell with the PCV.

What do you think?
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  #12  
Old 08-13-2008, 10:08 PM
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Quote:
Originally Posted by CJ7Taz View Post
Did though didnít it?

Try replacing the hose to the PCV valve. My guess is either it cracked when you moved it or the new PCV valve isnít sealing because the old hose is hard.
Brand new hose with the new PCV. Got good vacuum at idle.

I think I will see if I can get my hands on compression and vacuum gauges and see what I have.
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  #13  
Old 08-13-2008, 10:12 PM
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Originally Posted by spook2 View Post
I had the same problem on my first jeep. At the end of the day the rings were shot. I'm guessing the best thing for you to do right now is head to autodrone and borrow a compression tester and have at it.
My first thought. But if I have a broken compression ring, would the leaking compression into the crankcase not create enough pressure to blow the oil out at high idle? I ran it 1 1/2 hours on high idle and not one drop blew out the dipstick tube. I drove it 1.6 miles and several ounces blew out. I will check the compression anyway as well as vacuum.

Thanks.
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Old 08-13-2008, 11:07 PM
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When the engine is running, not cranking - pull the PCV Valve out of the grommet, leave it attached to the hose. Feel the hole in the end of the Valve. It should have strong vacuum on it. When you put your thumb over it, you can feel the strong vacuum.

The rattle is a valve inside that slams shut in case of backfire. Normally it should be open and free. In a backfire the air is going the wrong way, closing the valve.

If the valve was made wrong - or the part number was stamped on the wrong one, it could be internally backwards. This wouldn't be the first time a mfgr made something backwards.

Does it still blow oil out when you put the old PVC Valve in?
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Old 08-14-2008, 06:34 AM
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Quote:
Originally Posted by RRich View Post
When the engine is running, not cranking - pull the PCV Valve out of the grommet, leave it attached to the hose. Feel the hole in the end of the Valve. It should have strong vacuum on it. When you put your thumb over it, you can feel the strong vacuum.



The rattle is a valve inside that slams shut in case of backfire. Normally it should be open and free. In a backfire the air is going the wrong way, closing the valve.

If the valve was made wrong - or the part number was stamped on the wrong one, it could be internally backwards. This wouldn't be the first time a mfgr made something backwards.

Does it still blow oil out when you put the old PVC Valve in?
Yes, I did that, as posted in my orig question, strong vacuum on PCV valve when it is removed from the grommet. It is possible I am loosing vacuum when the engine is pulling. I need to put a gauge on it and test it while driving.

Bad move on my part, I threw the old one away. I have to go to the parts store today so I will try another new one and see what happens. Maybe I'll try NAPA this time.
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  #16  
Old 08-14-2008, 07:02 AM
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I hope you interpreted it like I meant it. Not vacuum "to" the valve, but "through it." I think you did it right though.

That shows the valve is open and free - the only other possible thing a "defective" Valve could be is the orfice is too small - it can't handle the volume at speed. But even then, if should be evacuating the crankcase enough not to blow the oil out of the dipsick tube.
It takes a goodly amount of pressure to force oil out the tube.

At idle, try holding your hand over the oil filler hole, you should not feel any pressure there - if anything, you should feel a little vacuum.
And - in a dark room or night, shine a strong flashlight beam across the open oil filler hole. If it's "blowing out" you should see fumes coming out. If it's "sucking in" like it should you won't. Then try blowing a puff of cigarette smoke at it - it should pull it out of the air.

How does the engine run otherwise? Smooth at speed and at idle?

If you have a vacuum gauge handy, it may help to look at it. Notice the vacuum at idle AND most importantly whether the vacuum is stable - not fluctuating - "ticking". Make sure when you hook it up you use a very short hose. With a long hose the hose acts like a buffer and hides the "ticking."

Did you do anything else at the same time as changing the valve? Like removing the EGR valve, if any?
Or tightening the manifold bolts?

A compression test will probably show a very low cylinder.

Has it overheated recently?
Also check for exhaust in the water, I'm wondering if exhaust is getting back into the crankcase at speed somehow (like a cracked head or head gasket,) pressurizing it more than the PCV can handle.


What really is the mystery is WHY it was coincidental with the PCV Valve change. Dumb luck?
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Old 08-14-2008, 03:34 PM
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Are you sure the PCV hose is not collapsing under vacuum?
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Old 08-14-2008, 07:02 PM
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That's what I meant. Pulling thru the PCV.

Ok, here's what I did today. I don't normally go to NAPA because they are several miles out of my way but I did today. Turns out the guy who owns the local franchise is a Jeeper! He has a '73 CJ5. So we chatted. He said that it is not uncommon to have bad PCV's out of the box. He also said that NAPA has advised that a "rattling" PCV does not necessarily mean it's ok.

So, I used to own a '73 but mine was a V8 so I asked him about his which was a 4.2 also. He suggested I try a vented oil fill cap like his has. I put one on, plugged my PCV back into the grommet and took off. I drove about 10 miles, nothing off road or abusive, got back home and my engine is dry as a bone! I had driven it less than 5 miles before and it blew over 1 quart out the dip stick tube.

Turns out that he did not have a PCV for my engine in stock and ordered me one. I'll pick it up next time I'm over that way and I will install it as well.

I addressed each of your points below as well. Thanks!

Quote:
Originally Posted by RRich View Post
I hope you interpreted it like I meant it. Not vacuum "to" the valve, but "through it." I think you did it right though.

That shows the valve is open and free - the only other possible thing a "defective" Valve could be is the orfice is too small - it can't handle the volume at speed. But even then, if should be evacuating the crankcase enough not to blow the oil out of the dipsick tube.<That is possilbe. I may have the wrong valve. I ordered a new one.>

It takes a goodly amount of pressure to force oil out the tube.<It blew over 1 quart out in less than 5 miles at less than 25 MPH.>

At idle, try holding your hand over the oil filler hole, you should not feel any pressure there - if anything, you should feel a little vacuum.< Small amount of vacuum>

And - in a dark room or night, shine a strong flashlight beam across the open oil filler hole. If it's "blowing out" you should see fumes coming out. If it's "sucking in" like it should you won't. Then try blowing a puff of cigarette smoke at it - it should pull it out of the air.

How does the engine run otherwise? Smooth at speed and at idle?
<Runs great!>

If you have a vacuum gauge handy, it may help to look at it. Notice the vacuum at idle AND most importantly whether the vacuum is stable - not fluctuating - "ticking". Make sure when you hook it up you use a very short hose. With a long hose the hose acts like a buffer and hides the "ticking."

Did you do anything else at the same time as changing the valve? Like removing the EGR valve, if any? <No>

Or tightening the manifold bolts? <No>

A compression test will probably show a very low cylinder. <That is what I'm afraid of! I will do it soon as I can borrow one.>

Has it overheated recently? <No>

Also check for exhaust in the water, I'm wondering if exhaust is getting back into the crankcase at speed somehow (like a cracked head or head gasket,) pressurizing it more than the PCV can handle. <Water looks fine. No bubbles like a compression leak into the cooling system>


What really is the mystery is WHY it was coincidental with the PCV Valve change. Dumb luck?
<My thoughts exactly! WHY? I feel sure it is an issue with the particular PCV I have. Wrong one, defective, etc.>
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Old 08-14-2008, 07:04 PM
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Quote:
Originally Posted by jeeperjohn View Post
Are you sure the PCV hose is not collapsing under vacuum?
Positive. It's brand new. And I observed it under vacuum.
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Old 08-14-2008, 09:29 PM
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That tells quite a bit - that the vented cap stopped it.

Normally the cap's blocked or sealed, or has a tube running to the air cleaner. Or there's another tube from the air cleaner that lets fresh air into the engine. It has to get fresh air in to sweep out the gasses through the PCV Valve.

Under normal operation that tube sucks clean fresh air into the engine - from inside the air cleaner - filtered clean air.

Under load when blowby is at it's highest, the PCV Valve cannot handle the volume, so the air in that air cleaner tube reverses direction, pushing the excess gasses into the air cleaner where the carb burns them. It's kind of an overflow bleed.

But - if that hose was plugged or restricted, and the PCV Valve was too small or restricted, then pressure builds up in the engine. It has to go somewhere, so out the tube it goes, carrying oil with it.
The worst part about that - worse than the mess, it can blow out the rear main seal - requiring lots of work. It's going to get out somehow!

Glad you got a handle on it. If it has to be smogged, you'll have to go back to the tube to the air cleaner for the test, so save it for later.

You may have a compression ring problem too that's giving more than normal blowby, I'd suggest a compression check too.
If compression is low in one cylinder, it may not be a bad ring, possibly just a stuck ring. Add some Techron to the gas tank, run it till it's gone, then add some Marvel mystery oil through that plug hole and let it sit a day or two. If it's just stuck, that usually frees it.

Let us know how the right valve works, and have a look at that tube.

Last edited by RRich; 08-14-2008 at 09:34 PM.
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