Oil in air filter

1992 4.0L HO, aw4, np231 ABS d35

Havin' some blowby issues, with oil in the air filter, and have read quite a few threads.

In response to the info I found I cleaned out my vaccum line from the valve cover to the intake manifold near the firewall that I understand to be the vaccum/pull side. I am also going to tackle the fresh air side that goes into the air box next, as well as replace the air filter to see if I'm doing any good.

Couple questions, though:

1. I thought I read somewhere that having a leaky valve cover gasket(which I have) can cause oil to be sucked into and blown onto the air filter...Is this correct? Should replacing that gasket be a priority in helping to solve this issue?

2. Down the line, in a couple months, if I decide to add a snorkel (it's ok to laugh, I can take it :wave1 do I have to consider that, when establishing a maintenence routine for the CCV system?

Thank you very much for any info.

SanDiegoOverland said:

1. I thought I read somewhere that having a leaky valve cover gasket(which I have) can cause oil to be sucked into and blown onto the air filter...Is this correct? Should replacing that gasket be a priority in helping to solve this issue?

2. Down the line, in a couple months, if I decide to add a snorkel (it's ok to laugh, I can take it :wave1 do I have to consider that, when establishing a maintenence routine for the CCV system?

Thank you very much for any info.

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1. No a leaky valve cover gasket can't cause what you are seeing. If it was bad, it might even help.

2. A snorkle shouldn't have much of an effect on what you are seeing.

The problem you are seeing is from worn piston rings. You can minimize the blow by issue by making the CCV line flow better. Pull the valve cover and completely disassemble the vent assy and clean it. Ideally replace the CCV hoses. They are surprisingly cheap at NAPA.

ok, I didn't understand that the piston rings were a consideration at this point.

Is there I timeline I should consider, as far as needing a rebuild goes, when the engine has this type of symptom?

The engine does not smoke except for a minimal puff upon start-up...and even then, never during the day, only first thing in the morning.

Does minimizing the blow-by help the engine stay lubricated?

thanks again, for info.

I'd sure take care to optimize the efficiency of the CCV system as oldman suggests before re-ringing your Jeep. Treat it to a new valve cover gasket and clean out the CCV system.

cruiser54 said:

I'd sure take care to optimize the efficiency of the CCV system as oldman suggests before re-ringing your Jeep. Treat it to a new valve cover gasket and clean out the CCV system.

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Ok, that'll probably be my next project.

Don't worry, you're engine isn't going to go out on you just because you have a little oil in the air filter from blow-by. I had 280K on an 87 XJ that I had to change the air filter every 6-8 weeks because how much oil was saturating it. Just keep an eye on your oil levels weekly which is over kill for some people but I just do it when filling up at the gas pump.

In short, don't rebuild your engine b/c you have blow-by.

BruceB83 said:

Don't worry, you're engine isn't going to go out on you just because you have a little oil in the air filter from blow-by. I had 280K on an 87 XJ that I had to change the air filter every 6-8 weeks because how much oil was saturating it. Just keep an eye on your oil levels weekly which is over kill for some people but I just do it when filling up at the gas pump.

In short, don't rebuild your engine b/c you have blow-by.

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10-4, I think I'll seal up all my leaks, clean the CCV system, run a bit heavier weight oil, and see how she does.

At 185k miles the darn thing still has rock solid oil pressure, is smooth as snot at 65, has ton's of power, and gets 19-20mpgs consistantly.

3-4 bucks in oil every few weeks 'aint too much to ask, I guess.

If there are any hippies reading this i didnt post it, but i have the same issue even after replacing the valvecover gasket and ccv lines. I added a piece of vinyl tubing, and clamped it to the rubber boot on the valve cover. I ran the tubing over the intake manifold and dropped it strait down over the steering shaft knuckle. You can either get a 5/8ths rubber cap and cover the breather on the Cleaner box or do what i did. I ran 5/8ths heater hose from the little breather to the A/C compresser when i turned it into a Air compressor. Just my $.02

brian, that puff of smoke upon start up may be from oil getting by the air filter due to there being so much. but i could be wrong. might have a look in the intake tube leading to the throttle body. but like they said, fix what you know whats wrong and see where that takes you.

I re-routed the whole thing, and put a little breather filter on the top of my valve cover... It has worked great.

Let me see if I can find the write up

Ok, so I finally got a chance to do a compression test.

starting @ the grill side of the block

1. 120
2. 121
3. 118
4. 120
5. 128
6. 120

Pretty darn good if you ask me. my references say that I can have a 30psi max variance, so I'm pretty stoked that it's 10psi

I re-checked 3, and again got 118, but the plug looks good, so I'm not too worried about it. Actually, all of them looked pretty damn nice. No fouling at all. Maybe some ashy-ness, and tan build up which to me could be from a few vacuum leaks creating a lean condition, maybe...

So with compression numbers like that, some blowby at the oil filler, and oil in air filter, would anyone venture to guess what my main issue is?

Hard for me to believe that its my rings. Can higher crankcase pressure simply come from poor vacuum/plugged orifices, etc?

My next move is to pull the valve cover, clean everything and replace all the hoses I need to.

Yeah, you need to make sure the CCV is serviced thoroughly.

SanDiegoOverland said:

My next move is to pull the valve cover, clean everything and replace all the hoses I need to.

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Compression is fine.

Pull valve cover, thoroughly clean, replace ALL ccv hoses. That goes a LONG ways towards the symptoms you are experiencing.

I ran an 88 Comanche for a long, long time by doing the above. One technician that I talked to said my engine was toast. He was WRONG.

joe_peters said:

Yeah, you need to make sure the CCV is serviced thoroughly.

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10-4