oil blow by problem

[blk88]

I have an oil blow by problem that I can't rid. I have had the valve cover glass bead cleaned and I have replaced all of the vacuum lines on top of the motor. I can drive in the city just fine with no blow by. As soon as I get on the highway and have to climb some highway grades, raising the rpms for a length of time, when I let off the accelerator to turn off to the trail the motor pukes oil in my air box and I have a large smoke screen. One of my thoughs is that I beleive I don't have a good seal on the rear of the oil pan because when it pukes oil I have a smoke screen as well from oil dropping on the exhaust pipe just below the rear of the oil pan. I think the oil pan seal is my smoke screen problem, but I'm stumpped about the oil in the air box. I was thinking that the seal issue might be the reason why the motor pushes oil up through the air box??? I want to drive my XJ to further trails than local stuff, but when I have the blow by issue I loose about 1/2 to 3/4 of a quart of oil and I'm afriad to drive more that 40-50 miles out of town. Any thoughts?

 

[vortex]

I have the same problem. One time i forgot to put my oil filler cap back on and drove about 50 miles to the trail and no smoke screens or anything so its probably your PCV valve....but mine happened to be the oil adapter O rings.

-PJ-

 

[blk88]

I have an '88 Renix motor so the don't have a PCV valve. I forget what it's called but it's an orfice and I've replaced that too. I've seen people replace the breather line to the filter box with a small filter on top of the vavle cover. What does that achieve and could that help my situation?

 

[fyrfytr1717]

That way when it pukes it fouls the small filter instead of your main filter.

 

[winterbeater]

It sounds like your piston rings are shot and the blowby is too much for the crankcase ventilation system to handle. It's supposed to make the heavy pollutants be run back into your engine. If you change that to a breather, you'll be putting a lot of smog out into the air. That's the way it was back in the early '60s. If it's forcing oil out of your rear seal too, you have a lot of pressure in there. You'll still burn the same amount of oil unless the breather lets out more air than the hose going back to the air intake does now..

 

[.40CalPatriot]

I have an '88 Renix motor so the don't have a PCV valve. I forget what it's called but it's an orfice and I've replaced that too. I've seen people replace the breather line to the filter box with a small filter on top of the vavle cover. What does that achieve and could that help my situation?

I did that. But only for one day. The small filter let out too much oil/gas smelling gases that filled up the cab while running ac/heat!

 

[Muddy Beast]

Try this mod...
http://www.jeepforum.com/forum/showthread.php?t=184475&page=2

I just did it because my vaccum line litterally slipped off somewhere and when I noticed it missing, I knew it was time for a mod. Even with duck tape on all of the hoses, everything would slide off if I didn't watch it. This thing cost me maybe $40, but it works great!




~Scott

 

[blk88]

It sounds like your piston rings are shot and the blowby is too much for the crankcase ventilation system to handle. It's supposed to make the heavy pollutants be run back into your engine. If you change that to a breather, you'll be putting a lot of smog out into the air. That's the way it was back in the early '60s. If it's forcing oil out of your rear seal too, you have a lot of pressure in there. You'll still burn the same amount of oil unless the breather lets out more air than the hose going back to the air intake does now..

IT CAN'T BE!!! I just replaced my motor 1.5 years ago with a used pulled motor about a year ago for the same reason. I was told the compression #'s were 140+/- on all cylinders. I'm worried that it might be true. I think I'm going to need to get a remanufactured motor. I'm running 4.88's and at highway speeds the rpm's are about 2.5k to 2.75k. My speed is about 65 -70mph. and I top out about there. I guess the used motor is tired and can't maintain that rpm for that length of time???

 

[Muddy Beast]

IT CAN'T BE!!! I just replaced my motor 1.5 years ago with a used pulled motor about a year ago for the same reason. I was told the compression #'s were 140+/- on all cylinders. I'm worried that it might be true. I think I'm going to need to get a remanufactured motor. I'm running 4.88's and at highway speeds the rpm's are about 2.5k to 2.75k. My speed is about 65 -70mph. and I top out about there. I guess the used motor is tired and can't maintain that rpm for that length of time???

I wouldn't stress it, from my understanding it's typical for the XJ's to blow oil back. And the older the engine, the worse it looks (hints why mine is so brown). It's better to have it blow into a can than have water cycle back into your engine IMO.

~Scott

 

[blk88]

I've seen the catch can fix before now you post it. I might give it a try. I'm not big on fixing a problem without solving it, but $40 is a lot cheaper than a new motor right now.

 

[Johnnie Walker]

Have you tried using some of that "engine restore" stuff and maybe some MMO to see if that helps at all? Sometimes it does.

 

[kidarkitect]

I've worked at a Jiffy lube on and off for the last 6ish years (while trying to get through college) and I haven't seen a single 4.0 that doesn't do this, including my own renix (89)

Its a jeep thing, now you understand.

Muddy beast's post looks like a good way to combat this though.

 

[blk88]

Every oil change I use engine restore and a synthetic oil to help. I'm not sure it helps but since it's my weekend warrior the cost isn't that much of a factor. I think I will be making a catch can until I can get a different motor. Thanks guys.

 

[kujito]

Change/clean both of the fittings which come off of the top of the valve cover. Clean/change the associated hoses as well. The orifice in the rear fitting is quite small, and clogs easily. The resulting back pressure forces oil back out the intake side(front fitting) and onto the air filter. The little filter thing will not only cause the escaping oil to run down the sides of the motor once the element is saturated, the vehicle will not pass emissions testing if your state does it.
Be very careful when removing the fittings because they like to tear and leave the bottom half of the grommet inside. I didn't find the 90* fitting at the front for a while, but I did discover that the parts store had a grommet that would fit the hole and the hose fit inside the grommet. I check on it regularly and it has so far stayed put.
HTH

 

[CJR]

Blk88,

Blow-by can come from piston rings gummed-up/stuck in the compressed position or excessively worn rings or broken rings. Likewise, worn valve guides can cause blow-by. I had the same problem on my 88, and when I pulled the engine (at 386,00 miles) to rebuild it, I found a broken ring.

Things you can do if rings are stuck in a compressed position; pull all the plugs and use one can of Gum-Out to spray in all cylinders. After finishig the can, let the engine set for awhile to let the Gum-Out loosen any stuck rings. Replace plugs, and start engine. You'll get alot of smoking initially and the rings should be free. Any Gum Out that leaks into the crankcase will evaporate eventually. If problem still exists, you can try installing new valve guide seals. If you still have the problem then you'll need to rering the engine/rebuild. Some Jeep dealers play the "replace the valve cover+ new emission hoses" scam for a temporary fix ($$$$) of blow-by.

Hope this helps.

Best regards,

CJR

 

[joe_peters]

Might not be in any way related, but I noticed oil on the back of 90 4.0 rear hatch after a 200+ mile trip.

This had never happened before.

Checking the engine compartment, I noticed that the "J" shaped hose from the air intake (air box if stock) that connects to the vacuum harness and is the air intake to the front of the valve cover for the CCV was completely flat. Pulled the "J" hose, looked OK on outside but completely deteriorated on inside.

Went to Autozone and found a similar hose, installed it, no more oil on rear hatch.

There is always going to be compression blow by in the crankcase, no matter what the condition of the compression rings. If the CCV system is functioning correctly it should handle things OK. Yes, positive pressure (clogged CCV system) can force oil out of the engines seals, we saw this on Volvos front and rear mains and the cam seal. Volvo screwed the pooch in the early eighties and reduced the size of the brass flame trap in their CCV system. Once that CCV system clogged up you could read 10-17 lbs pressure with a gauge at the dipstick tube.

Regret the long post. Check and repair the CCV system and see what that gets you.

 

[Red90Laredo]

I just got done cleaning up my 90 renix valve cover last night. I spent about 3 hours off and on cleaning it. As mentioned above the rear grommet that connects to the small line was plugged with crusty oil.

I took everything that would come off out and cleaned it good. I will replace the small diameter line with hard brake line since it is probably clogged too.

I installed a little breather in the spot that usually connects to the air box. We'll see what happens, I'll report back. I know some of you say the breather fix doesnt work- but did you clean out/repair the rest of the system?

 

[joe_peters]

You haven't had it bead-blasted and powder coated yet? LOL!

You're right, all of the system components must be functioning for the CCV to work. You simply put a breather on the vc to eliminate the air intake hose from the intake. Looks good.

Only concern, and don't know about AZ where OP lives, that wouldn't pass a visual inspection for smog.

 

[Red90Laredo]

naw, if I was still working at a place with a media blast cabinet I would have hit it, but I dont really care what it looks like. You have to watch media blasting too cuz you can hit it too much too fast and warp the part with the heat created.

It's just nice to be able to handle the thing without latex gloves or washing up right afterwards.

 

[joe_peters]

Buddy of mine has a Cuda parts washer. Sometimes when I'm working on dirty parts I have this urgent need to purchase a couple of Big Kickers from Dutch Bros. and go visit him! LOL!