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Unread 11-03-2012, 11:12 PM   #1
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89 yj 4.2 engine building pressure

Hi i am new to this forum. I have just recently picked up this 89 yj wrangler with the 4.2 5spd, it didnt run when i got it and it need a it of work, i have it running now, but for the past week or so ive noticed oil on the garage floor. And today i took the air cleaner cover off and there was a pool of oil inside. It had also been pushing out the top of the cover where the bolt for the wing nut is. Can anyone tell me what the most likley problem is? Its seeming like its building up pressure and just pushing oil everywhere. Any suggestions would help. Thanks

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Unread 11-03-2012, 11:44 PM   #2
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Post in YJ tech. You'll get more answers there. With what your describing though it sounds like the ccv is clogged and just needs a good cleaning. It's cheap and easy to do. Blow by is the other common culprit but don't borrow trouble yet. You should however also do a compression test. That will tell you if you have blowby

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Unread 11-04-2012, 01:06 AM   #3
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I dont think the 4.2 had the CCV but maybe they did in the later years, anyway verify the CCV or PCV system is working and the vacuum line(s) are connected, not leaking or clogged. It is possible that the old engine is tired and the rings are wore causing excessive blow by. Blow by gasses getting passed the pistons and through the crankcase will pick up oil vapors and then they will collect in the tube or air filter housing. Dealing with this problem can get worse on engines that see high load and/or high speed like highway driving or towing.

If the cause is blow by then search for threads about making a catch can or draft tube. Some people route the breather tube down the engine toward the ground so it doesnt foul the air filter and intake with oil. Some people rig up a catch can to trap the oil too, both are easy mods.
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