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Unread 04-20-2013, 07:58 AM   #1
Skerr
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PCV/Vacuum/DS Oil Leak/ HELP!

I don't know what else to do to fix this problem. I think I remember reading somewhere about rings and blow-by?? I need to know how to solve this riddle.

This is a 1979 258 with unknown miles. Team Rushed, MC2100. 21 hG of manifold vacuum. It runs well and has lots of get-up-and-go. Everything was hunky-dory until it started blowing oil out of the dip stick tube. I investigated the PCV setup. I ended up gutting a PCV valve and reattaching it to the valve cover (I didn't really understand why there had to be a valve inside the PCV, and I wanted to be sure it was open). Whatever else I did caused the engine to run well with no issues.

Now it is blowing oil out of the DS tube again. I discovered my manifold vac had dropped to 15 hG. I found the 90* plastic elbow on the PCV to be leaking. I thought I had dropped enough hG vacuum that the engine was not evacuating the crankcase pressure sufficiently. I picked up another PCV from AZ, with the elbow, and plugged it in. I am back to 21 hG vacuum. Wifey and I went for a ride yesterday, and when we came out of Fastenal I saw a significant puddle under the Jeep! The side of the engine was coated!! I went back in the store, bought some black tape, and pulled/plugged the PCV, allowing the crankcase to vent through the opening in the valve cover. ZERO oil pressure at this point, stopped and added 2 quarts.

Why am I having this issue?? Here are some pics to look at... this is where I am at right now. There are no leaks that I can find. Hose fittings are tight. All hoses are very recent, not old or cracked. Jeep has power brakes.

Thanks.

Port where I tested vacuum.
Plugged PCV.
Oil-coated engine.
PCV port on carb base.
Valve cover left open with filtered vent in the back.

cimg0927_1.jpg   cimg0928_1.jpg   cimg0932_1.jpg   cimg0934_1.jpg   cimg0936_1.jpg  

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Unread 04-20-2013, 08:47 AM   #2
Joe73CJ5
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How does the PVC hooked up? Does it go straight to a vacuum source or charcoal canister? Do you have the same problem of coming out of the dipstick with the PVC out of the valve cover?
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Unread 04-20-2013, 11:48 AM   #3
Skerr
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Quote:
Originally Posted by Joe73CJ5 View Post
How does the PVC hooked up? Does it go straight to a vacuum source or charcoal canister? Do you have the same problem of coming out of the dipstick with the PVC out of the valve cover?
PCV is straight from the valve cover into the carb base. The line is not shared, but dedicated. There is no canister on this Jeep. No oil leak with the valve cover vented to the atmosphere.
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Unread 04-20-2013, 02:41 PM   #4
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I would hook the PVC to manifold vacuum. For me it worked better. I also bought a vented cap for the oil fill hole. I run the distrib from the carb vacuum. You should also check compression. Are your plugs really oily?
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Unread 04-20-2013, 07:07 PM   #5
Skerr
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Quote:
Originally Posted by Joe73CJ5 View Post
I would hook the PVC to manifold vacuum. For me it worked better. I also bought a vented cap for the oil fill hole. I run the distrib from the carb vacuum. You should also check compression. Are your plugs really oily?
The port at the carb base is manifold vacuum, and there is a vent at the rear of the valve cover. Distributor is run from the carb on ported vacuum. I have not checked compression or plugs yet.
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Unread 04-20-2013, 07:46 PM   #6
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OK. Also there should be some type of gasket on the dipstick ring. I have also heard where the dipstick ring comes loose and moves and not seals well, small chance though. Can't think much else.
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Unread 04-20-2013, 08:14 PM   #7
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Skerr, I had the exact same issue in the last week. Last weekend I replaced the front and rear oil seals (both were leaking), and the timing chain cover gasket and oil pan gasket as well (not much choice since they were destroyed to get at the seals). After this I ended up with one major leak left... The dip stick tube. The first thing I did after that was to fix the PCV valve arrangement. What the PO did to this wasn't working. So I now have a PCV valve connected to the base of the carb, as you do. At the rear of the valve cover I used an elbow and hose to go into the air cleaner, which is essentially the same thing you have.

This didn't stop the oil leak, though I'm sure it is better for the engine than what was there before.

I read in a couple of threads on here that excessive blow-by was the most likely culprit, and gunked up piston rings or worn rings being the two most likely causes. I'm planning to rebuild the 258 from my parts jeep with a MPFI head from a 92 Cherokee later this summer, so taking this engine apart to do a ring job is not in the cards. Instead, I went with the theory that the rings might just be clogged with buildup. I added 3oz of Lucas fuel treatment to the tank, figuring it couldn't hurt, and I used a product called Motor Flush (twice). It's essentially a quart of stuff you pour into the engine with your oil that will clean it. You run the engine for five minutes with this stuff (it's a lot like kerosene) and then dump it out, replace the filter, and fill with new oil. I repeated the process as recommended for older engines (and since I was having such a problem with blow by I figured I needed it).

Much to my surprise it worked. When I drove my jeep to work the next day there were only a few drops of oil on the side of the motor. After three or four days of driving back and forth to work (30 miles each way) my oil level is still at full. I didn't do anything else that might have effected a change, so one or both of those must have done it.

It cost me about $15 for the Lucas oil treatment and two containers of the motor flush, plus the oil and filters to do two oil changes. Much cheaper than a motor rebuild. Hope this helps and good luck.
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Unread 04-21-2013, 08:05 AM   #8
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Had the same thinks happen to a bronco.
Pull the valve cover off and clean the PVC vent in the valve cover. It gets gunked up and whatever blow-by you have will put the engine under positive pressure. Oil will either come out the dipstick tube or a gasket.
I cleaned it up and it worked great.
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Unread 04-21-2013, 05:26 PM   #9
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Quote:
Originally Posted by EgulAye View Post
Skerr, I had the exact same issue in the last week. Last weekend I replaced the front and rear oil seals (both were leaking), and the timing chain cover gasket and oil pan gasket as well (not much choice since they were destroyed to get at the seals). After this I ended up with one major leak left... The dip stick tube. The first thing I did after that was to fix the PCV valve arrangement. What the PO did to this wasn't working. So I now have a PCV valve connected to the base of the carb, as you do. At the rear of the valve cover I used an elbow and hose to go into the air cleaner, which is essentially the same thing you have.

This didn't stop the oil leak, though I'm sure it is better for the engine than what was there before.

I read in a couple of threads on here that excessive blow-by was the most likely culprit, and gunked up piston rings or worn rings being the two most likely causes. I'm planning to rebuild the 258 from my parts jeep with a MPFI head from a 92 Cherokee later this summer, so taking this engine apart to do a ring job is not in the cards. Instead, I went with the theory that the rings might just be clogged with buildup. I added 3oz of Lucas fuel treatment to the tank, figuring it couldn't hurt, and I used a product called Motor Flush (twice). It's essentially a quart of stuff you pour into the engine with your oil that will clean it. You run the engine for five minutes with this stuff (it's a lot like kerosene) and then dump it out, replace the filter, and fill with new oil. I repeated the process as recommended for older engines (and since I was having such a problem with blow by I figured I needed it).

Much to my surprise it worked. When I drove my jeep to work the next day there were only a few drops of oil on the side of the motor. After three or four days of driving back and forth to work (30 miles each way) my oil level is still at full. I didn't do anything else that might have effected a change, so one or both of those must have done it.

It cost me about $15 for the Lucas oil treatment and two containers of the motor flush, plus the oil and filters to do two oil changes. Much cheaper than a motor rebuild. Hope this helps and good luck.
Thanks EA... I thought I remembered reading about ring wear, which is beyond my compression ()! I may look into a 4.0 head swap or even another engine. I guess the sky's the limit now. I have gone through a tank of fuel system cleaner, but not something complete with the fervency as you. Since I work PT at AZ I can get this stuff at a discount, so I will try it in the interim.

Quote:
Originally Posted by gwolff View Post
Had the same thinks happen to a bronco.
Pull the valve cover off and clean the PVC vent in the valve cover. It gets gunked up and whatever blow-by you have will put the engine under positive pressure. Oil will either come out the dipstick tube or a gasket.
I cleaned it up and it worked great.
wolff... I'll investigate under the valve cover, but I feel pretty good about it. It has been only a few months since I pulled it off and reseated it with a new VC gasket. But I've certainly been humbled before!!! Thanks
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Unread 04-21-2013, 08:11 PM   #10
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If you remove your dipstick and hold your finger over it can you feel a vacuum when you remove your finger?

Or pull the breather you have near the firewall and block the hole with your thumb and see if a vacuum builds.

Factory was not that breather. It was a 90 degree plastic fitting that had a hose running to a port in the aircleaner with a fiber pad I side the port.
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Unread 04-23-2013, 04:40 PM   #11
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Quote:
Originally Posted by 86cj74.2L View Post
If you remove your dipstick and hold your finger over it can you feel a vacuum when you remove your finger?

Or pull the breather you have near the firewall and block the hole with your thumb and see if a vacuum builds.

Factory was not that breather. It was a 90 degree plastic fitting that had a hose running to a port in the aircleaner with a fiber pad I side the port.
86, what other criteria do I need in this scenario? PCV hooked up, blocked off, etc? SHOULD there be a vacuum at the DS tube?

Pull the breather at the firewall, with everything else correctly connected (?) and check for a vacuum forming? It was my thought (using the term loosely) that the valve cover needed a fresh air source and the PCV. Maybe the breather is reducing the vacuum so much that the crankcase pressure is not alleviated through the PCV??

Thank you
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Unread 04-23-2013, 05:32 PM   #12
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Quote:
Originally Posted by Skerr

86, what other criteria do I need in this scenario? PCV hooked up, blocked off, etc? SHOULD there be a vacuum at the DS tube?

Pull the breather at the firewall, with everything else correctly connected (?) and check for a vacuum forming? It was my thought (using the term loosely) that the valve cover needed a fresh air source and the PCV. Maybe the breather is reducing the vacuum so much that the crankcase pressure is not alleviated through the PCV??

Thank you
Leave your PCV hooked up and pull your breather and put your thumb over the rubber grommet. See if it builds vacuum.
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Unread 04-23-2013, 05:36 PM   #13
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If the breather is at the back of the valve cover, away from the fan, you can often see it try to pull the corner of a piece of paper into the valve cover if it's working (breather removed, of course)


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Unread 04-23-2013, 05:58 PM   #14
86cj74.2L
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The factory setup is it sucking fresh air through a small 1/4 plastic orifice and a piece of fibrous material around as dense as a brilla pad.

Not a big honkin breather.

You can also convert to the fixed orifice type like the newer 4.0's have.
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Unread 04-24-2013, 10:29 AM   #15
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Quote:
Originally Posted by Skerr View Post

wolff... I'll investigate under the valve cover, but I feel pretty good about it. It has been only a few months since I pulled it off and reseated it with a new VC gasket. But I've certainly been humbled before!!! Thanks
Skerr,

Did you take pictures when you changed the valve cover gasket? If so,post a couple here. Anything of the inside of the cover or top of the motor would be good.
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