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Unread 01-19-2014, 09:30 PM   #1
geusey
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4.0 Oil Everywhere at High Speeds

1992 4.0 YJ with 161,000 miles. It blows an excessive amount of oil into the air filter, but only while driving at higher speeds (70 - 75 mph). It does not really blow any oil - or at least not a noticeable amount - while driving in town, just at freeway speeds. I've replaced all the little hoses and grommets in the CCV system and cleaned the valve cover inside and out, nut it still does it at freeway speeds. It is to the point that it soaks the entire airbox and oil drips down onto the frame and causes oil stains under the jeep right by the left front tire. So, yeah, it's pretty bad, but its only this bad when driving at freeway speeds.

I threw a breather filter on the valve cover and capped the hole to the air box to at least keep it from soaking the air filter, but now it just blows oil out of the breather filter and drips out onto the exhaust manifold causing it to smoke like crazy! (again, only at freeway speeds, its not really a problem driving in town or at speeds below 70 mph)

The valve cover is actually not the original, it is from an 87 Cherokee 4.0 that was put on there several years ago.

So here's my question. Could it be some kind of incompatibility with the valve cover that is on there which would be fixed by buying a proper valve cover for that year model of wrangler? I always assumed the only difference in those valve covers was the style of grommet and type of oil filler cap (since they are both for 4.0's), but could there be something else about it that is making it not work well at higher speeds?

Or do I need to start thinking about piston rings or something else that could be a serious issue down the road?

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Unread 01-19-2014, 11:36 PM   #2
GrEmLiN
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Do a compression test on all cylinders to make sure it's not just one bad cylinder, and you can get a universal oil separator from Summit Racing to deal with it in the mean time, but you have blow-by. The valve cover has nothing to do with this problem. My 258 when I blast 80 up the highway and spin the engine faster than it needs to, it blows lots of oil, blows the pcv out of the valve cover.

Whats your idle oil pressure like? What about running/cruise oil pressure?

You can get a cylinder hone from AutoZone and hone the cylinders with an electric drill and get new piston rings. If you're gonna go so far as to do rings you can consider doing the machine work and bearings, and have a rebuilt motor. Or in the mean time maybe you can try one of those snake oils to swell the piston rings.
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Unread 01-20-2014, 09:11 AM   #3
Louie4
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Like said above, you have some intense blow-by. If you do the compression test and it comes back good you may want to consider doing this swap:

4.0L Valve Cover Swap Write-up

It couldn't hurt and would be relatively cheap and help the engine breath better.
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Unread 01-20-2014, 06:59 PM   #4
geusey
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Sigh, okay.


Yeah, I think it's going to need surgery. I'll do a compression test when I get a chance and see what's going on in there, but all of my observations and research are pointing towards at least one bad ring. It's been steadily getting worse for a while now, so I really don't think it has anything to do with the valve cover either. Just want to make sure I didn't miss anything.


Louie, I saw that swap the other day. Looks like a good idea, I might start there. Even if it doesn't fix the problem, it's definitely a cheap and easy upgrade.
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Unread 01-21-2014, 06:18 AM   #5
Que89YJ
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I just went through a similar problem with another member. Pull the valve cover off and check to make sure the baffles are clear in the valve cover to allow it to vent. The fins were bent on his and it coused oil to blow everywhere because it couldnt vent. Do the compression test too. Remember you need to do a wet/dry cylinder test.
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Unread 01-22-2014, 09:41 PM   #6
geusey
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Quote:
Originally Posted by Que89YJ View Post
I just went through a similar problem with another member. Pull the valve cover off and check to make sure the baffles are clear in the valve cover to allow it to vent. The fins were bent on his and it coused oil to blow everywhere because it couldnt vent. Do the compression test too. Remember you need to do a wet/dry cylinder test.
Valve cover is good. Everything is clear. I'll be doing the compression test within a couple of weeks (I'll have to borrow the tool), until them the jeep isn't leaving town or going above 55. I will be back on here for updates when the test is done.
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Unread 01-23-2014, 08:21 AM   #7
Que89YJ
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For the member here someone had bent the vavle cover baffles so it would block the flow of air. The hose from the ccv was gummed up. It was a mess. 160,00 really isnt that many miles. Keep us updated.
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Unread 01-23-2014, 08:46 AM   #8
geusey
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Quote:
Originally Posted by Que89YJ View Post
For the member here someone had bent the vavle cover baffles so it would block the flow of air. The hose from the ccv was gummed up. It was a mess. 160,00 really isnt that many miles. Keep us updated.
Yeah, I know that's not a lot of miles, which is why i was quick to try and explain it away with other things, but I'm only responsible for 15,000 of those miles. Judging from the shape things were in when I got it, I don't think it was well taken care-of before me.

Will keep you guys updated.
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Unread 02-01-2014, 09:39 PM   #9
geusey
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Update:


After talking to my brother, he suggested it could also be a blown head gasket. He made a fairly sensible argument (said blowby could go straight through the gasket into the oil channel, causing positive pressure in the crankcase). Anyway, I checked in the radiator and I did find the slimey chocolate-milk-like substance that indicates oil in the coolant.


So, my brother was a navy diesel mechanic, but I will defer to the Jeep expert opinions on here. Obviously something is wrong (probably blown head gasket) to have oil in the radiator. Could this possibly be causing my blow-by issue, or have I been cursed with two crippling engine issues at once?
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Unread 02-01-2014, 09:47 PM   #10
jsawduste
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Your on the right track.
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Unread 02-02-2014, 05:33 AM   #11
Que89YJ
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Your brother knows. Compression test.
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Unread 02-18-2014, 07:38 AM   #12
geusey
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So, I bought an old pickup truck today to drive around while I am working on the Jeep. Rusty (the jeep) has officially retired from service as a Daily Driver. *salutes* Now that I don't have to drive it around and tote the family in it anymore, I'll be pulling the head off soon-ish.
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Unread 03-20-2014, 08:10 PM   #13
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Quick update:


Pulled the head and had a peek inside. The gasket looks fine and there aren't any noticeable cracks in the cylinder walls. However, upon checking the head with a straight edge, it appears warped. These can be repaired at a machine shop, correct? Or does it need replaced? Either way, I'll have it inspeted professionally to make sure.
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Unread 03-21-2014, 05:53 AM   #14
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Time to machine the head. Yes it can.
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Unread 05-19-2014, 06:05 PM   #15
geusey
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Update:
Selling my Ford truck to help pay for Jeep repairs. I am a teacher, so I can get by with just my wife's car for this summer. I can get the head machined and put the Jeep back together for a few hundred, OR........

I've been offered a 318 out of a 98 Dodge 1500 with under 50,000 miles for free. Shipped to me for free. I'm considering doing the swap, then rebuilding and selling the 4.0. Either way, I've got all summer to finish what I've started here.
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