Dkfiii88manche Posted March 31, 2015 Share Posted March 31, 2015 I have an '88 comanche. on the valve cover there's a hole with a half inch hose that goes down to my air box. My air filter gets covered with oil. I was wondering if a check valve is supposed to be there that lets the engine breathe but keeps the oil where it's s to be. Any insight would be greatly appreciated. Please help. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 31, 2015 Share Posted March 31, 2015 With the engine at idle, remove the oil fill cap and see if you can feel air being forced out. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 31, 2015 Share Posted March 31, 2015 Click on the link below to my tips. Read Tip 25. Also, make all your vacuum harnesses are in tact. See Tip 22. Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 7, 2015 Share Posted April 7, 2015 I had this problem on my truck about 5 years ago. Is your oil psi high? my oil psi was high and it was spitting that oil out to the box. What I did to solve the problem was to replace that back grommet and the ccv below it. not really a valve tho. You have to remove the valve cover to do so. It happen again a year or two later. so I took all that off and got a pcv valve and have not had the high psi oil and the spitting of oil to the box. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 7, 2015 Share Posted April 7, 2015 Every time this subject comes up, I ask the man to remover the oil fill while at idle and see if air is being forced out. And yet, I'm ignored. Laziness or fear? What is it? Link to comment Share on other sites More sharing options...
Megadan Posted April 7, 2015 Share Posted April 7, 2015 I still get oil in my air filter, but it greatly reduced after doing Cruisers Tip 25. My next step is to make a cheap air/oil seperator using an e-bay catch can with a couple of modifications. I know a big part of it is because of excessive blow by causing increased crankcase pressure (which is why Jeep Driver is asking you to do what he is suggesting). My engine was a little mistreated in years past and while it doesn't burn oil, it lets a lot of combustion and compression gasses get by the rings. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 7, 2015 Share Posted April 7, 2015 Every time this subject comes up, I ask the man to remover the oil fill while at idle and see if air is being forced out. And yet, I'm ignored. Laziness or fear? What is it? Search me.... And if air is being pushed out, the CCV system at the rear may be clogged or old. Did you guys know they changed it? The grommet and orifice/tube back there? Know why? Imagine this, but oil was getting in the air cleaner!!!! Tip 22 outlines the correct vacuum harnesses. The tube from the rear of the valve cover to the intake manifold is part number BK 715-1365 or Dorman 46005 and comes with the valve cover grommet. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 7, 2015 Share Posted April 7, 2015 No. If air is being forced out, your crankcase is over pressurized. Likely it is ring failure. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 7, 2015 Share Posted April 7, 2015 Well, they weren't experiencing ring failure when these things were under warranty........ That's when these fixes came about. Link to comment Share on other sites More sharing options...
Dillithium Posted April 7, 2015 Share Posted April 7, 2015 Also known as blow-by. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 7, 2015 Share Posted April 7, 2015 Also known as blow-by. Yes, of course. But no one can connect the dots, apparently. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 7, 2015 Share Posted April 7, 2015 Crankcases make pressure naturally. It's when the CCV system can't handle it that oil gets into the air cleaner. Can EXCESSIVE pressure contribute to it? Yes. Is some pressure indicative of ring failure? No. You guys probably weren't around when cars had a crankcase vent tube pointing to the ground where all the crankcase pressure went. Link to comment Share on other sites More sharing options...
Dillithium Posted April 7, 2015 Share Posted April 7, 2015 A clogged CCV or not, Jeepdriver's suggestion is a lot simpler than tearing into a vacuum harness or removing a valve cover. If there's little to no air being pushed out at idle, look further. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 7, 2015 Share Posted April 7, 2015 A clogged CCV or not, Jeepdriver's suggestion is a lot simpler than tearing into a vacuum harness or removing a valve cover. If there's little to no air being pushed out at idle, look further. So, how are we gonna quantify "excessive" pressure? How often do 4.0s have bad rings? Rarely. What if an unsuspecting newbie somehow thought his crankcase pressure was excessive so rebuilt his engine when it didn't need it? All it needed was the dreaded valve cover removal/modification and subsequent replacement of some inexpensive vacuum harnesses? A proper suggestion would be that if you suspect excessive crankcase pressure, have a leakdown test performed to verify. Link to comment Share on other sites More sharing options...
Rockfrog Posted April 7, 2015 Share Posted April 7, 2015 Well, I have a perfectly functioning CCV system ... And oil dripping through my filter. To say the PO neglected my motor is an understatement to say the least. But, on a good condition motor, cruiser is right, you will cure the issue by maintaining the CCV or updating it. On a motor at the other end of the scale ... Find other solutions ... The air/oil separator is my next plan. Not wanting to re-doing my motor for a wee bit o blow by just yet. She still pulls strong and runs great. So, admit it, your both right. Just on opposite sides of the same coin. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 7, 2015 Share Posted April 7, 2015 Well, I have a perfectly functioning CCV system ... And oil dripping through my filter. To say the PO neglected my motor is an understatement to say the least. But, on a good condition motor, cruiser is right, you will cure the issue by maintaining the CCV or updating it. On a motor at the other end of the scale ... Find other solutions ... The air/oil separator is my next plan. Not wanting to re-doing my motor for a wee bit o blow by just yet. She still pulls strong and runs great. So, admit it, your both right. Just on opposite sides of the same coin. Did you shorten the flutes in the valve cover? You know the problem with them is that they reached all the way down to the oil splash on top of the head. Took very little pressure from the crankcase to get oil to be sucked out the flutes. Link to comment Share on other sites More sharing options...
Jeepman Posted April 7, 2015 Share Posted April 7, 2015 I agree With Cruiser start with the simple things that are designed to control the crankcase pressure before going down the internal failure road... Link to comment Share on other sites More sharing options...
Megadan Posted April 7, 2015 Share Posted April 7, 2015 See, in my case, I know mine is excessive crankcrase pressure. You should see how badly my engine fails a leakdown test. It's not quite a hurricane out of the oil fill, but it's substantial. Link to comment Share on other sites More sharing options...
Rockfrog Posted April 7, 2015 Share Posted April 7, 2015 Well, I have a perfectly functioning CCV system ... And oil dripping through my filter. To say the PO neglected my motor is an understatement to say the least. But, on a good condition motor, cruiser is right, you will cure the issue by maintaining the CCV or updating it. On a motor at the other end of the scale ... Find other solutions ... The air/oil separator is my next plan. Not wanting to re-doing my motor for a wee bit o blow by just yet. She still pulls strong and runs great. So, admit it, your both right. Just on opposite sides of the same coin. Did you shorten the flutes in the valve cover? You know the problem with them is that they reached all the way down to the oil splash on top of the head. Took very little pressure from the crankcase to get oil to be sucked out the flutes. I did originally ... Then went one step further ... HO head, and the valve cover and CCV system off my '00 XJ (which has a 93 head and VC with no blood or oil in the filter). CCV was replaced with new parts back in October. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 8, 2015 Share Posted April 8, 2015 Well, I have a perfectly functioning CCV system ... And oil dripping through my filter. To say the PO neglected my motor is an understatement to say the least. But, on a good condition motor, cruiser is right, you will cure the issue by maintaining the CCV or updating it. On a motor at the other end of the scale ... Find other solutions ... The air/oil separator is my next plan. Not wanting to re-doing my motor for a wee bit o blow by just yet. She still pulls strong and runs great. So, admit it, your both right. Just on opposite sides of the same coin. Did you shorten the flutes in the valve cover? You know the problem with them is that they reached all the way down to the oil splash on top of the head. Took very little pressure from the crankcase to get oil to be sucked out the flutes. I did originally ... Then went one step further ... HO head, and the valve cover and CCV system off my '00 XJ (which has a 93 head and VC with no blood or oil in the filter). CCV was replaced with new parts back in October. I thought that green valve cover might be a later model one..... Link to comment Share on other sites More sharing options...
Zebvance Posted April 8, 2015 Share Posted April 8, 2015 How bout do a compression test and that will tell you. I had the same problem.I did the valve cover fix and new ccv harness all around. Stopped getting oil in the air box with a newer style valve cover without flutes. But the compression test ended up with low compression in #2. Drove it more and decided I needed to replace a few seals that were leaking. Rear main seal, oil filter adapter o rings, distributer gasket, valve cover gasket. Every time I replaced a gasket or seal a new leak would start in a area where I previously replaced the gasket that wasn't leaking before. Then I had a shop do what they called a pressure test and they told me the rings were the cause. The crankcase pressure would build up to 3 psi before getting to 30 mph. That's the reason I keep blowing seals. SO its time for a rebuild Link to comment Share on other sites More sharing options...
cruiser54 Posted April 8, 2015 Share Posted April 8, 2015 How bout do a compression test and that will tell you. I had the same problem.I did the valve cover fix and new ccv harness all around. Stopped getting oil in the air box with a newer style valve cover without flutes. But the compression test ended up with low compression in #2. Drove it more and decided I needed to replace a few seals that were leaking. Rear main seal, oil filter adapter o rings, distributer gasket, valve cover gasket. Every time I replaced a gasket or seal a new leak would start in a area where I previously replaced the gasket that wasn't leaking before. Then I had a shop do what they called a pressure test and they told me the rings were the cause. The crankcase pressure would build up to 3 psi before getting to 30 mph. That's the reason I keep blowing seals. SO its time for a rebuild That's the leakdown test I was referring to....... Link to comment Share on other sites More sharing options...
Rockfrog Posted April 8, 2015 Share Posted April 8, 2015 Mine only leaks through my distributor, about three drops a day ... It's pretty shot, just hummin' and hawin' about fixing it. Otherwise no leaks. I used a worn out 92 head ... And of course I forgot to replace the valve seals before installing it. Work called and my 2 weeks off turned into 4 days, things went back together quick fast ... She was down to the block. May have skipped a few steps. I do know the bore are fairly polished. Didn't have time for a hone, spent most of my time cleanning the crud out of the pan, timing cover, lifter gallery, and everywhere else. I'm guessing I'm losing compression through the seals and the Rings (may just be the seals if I'm lucky). She still motivates something nasty even pushing the 32's (265/75r17) with stock 3.07's though, a lot more than I expected after seeing the bores. Link to comment Share on other sites More sharing options...
metrictonner Posted April 8, 2015 Share Posted April 8, 2015 Actually the front hose coming off of the valve cover is THE crankcase breather. The part of the airbox that is attached to the throttle body intake hose is a venturi that is supposed to suck this crankcase nastyness back into the intake manifold for emission recirculation burning. This is why we periodically clean our throttle bodies. Your venturi sounds like it is clogged up or you are getting so much BLOW BY (yes indeed...ring job) that this recirculation system can't handle it. Burning much oil between changes? If so, you probably need a ring job, which is unusual for the 4.0. Check your air box top workings. Link to comment Share on other sites More sharing options...
metrictonner Posted April 8, 2015 Share Posted April 8, 2015 OOPs, check that. Its the gas tank vapors that are venturied into the intake manifold. The crankcase breather is dumped on the manifold side of the air filter. Oh well, today was Ferrari day. You probably have blow by problems if your crankcase ouput exceeds your intake manifold input. If you are not getting billowing smoke out the tail pipe then you are suffering from dreaded RING GAP ALIGNMENT. Either that or bad valve seals. The solution to the first is pop the head, punch the pistons, stagger the ring gaps, hone the cylinder walls and put the whole thing back together. The other is just a simple valve seal replacement. Link to comment Share on other sites More sharing options...
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