4.2 with Major issue...possible causes? - JeepForum.com

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post #1 of 4 Old 01-12-2006, 03:33 PM Thread Starter
Bgeddes's Avatar
1978 CJ5 
Join Date: May 2005
Location: NEPA
Posts: 1,237
4.2 with Major issue...possible causes?

A guy I work with has an '88 YJ in pretty good shape, only a little surface rust here and there, everything works, etc. Something very bad is going on in the engine. It's a straight 6 (so Im thinking it should be a 4.2?) , about 160,000 on the Jeep. It blows oil out the breather like crazy. He was driving it and stopped prior to it running out of oil (actually, it's only just over a quart low), and it turns over fine. It didn't start when I tried it but I didnt hear any noises indicating major bottom end problems. I'm think there are a few possibilities to cause this, a burned piston, cracked ring(s), or head gasket. Anyone seen this problem before particularly on the 4.2? I'm working on buying this rig as is and fixing for use as a trail rig. Here's the Wrangler:

'00 XJ Classic > Stock DD
'88 Grand Waggy - Bone stock pseudo-barnfind
'78 CJ5 - Under minor rehab
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post #2 of 4 Old 01-16-2006, 04:19 PM
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1987 YJ Wrangler 
Join Date: Mar 2004
Location: Upstate NY
Posts: 2,388
Could be something as simple as a bad PCV valve or clogged PCV hose. I'd check those first. Most 4.2s and 4.0s blow oil out the breather to some extent, but your case sounds too extreem to be normal.

'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
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post #3 of 4 Old 01-25-2006, 10:40 PM
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1997 TJ Wrangler 
Join Date: Nov 2005
Posts: 51
You Didnt Say If It Smoked Out The Tail... Very Important That...does It..or Not. Look In The Radiator..find Any Oil ?
Inline 6 Are Tanks.. Dam Hard To Hurt One.. Look At It This Way.. What Do You About The Engine Conidtion.. If Its A Trail Rig..your Going To Rebuild First Anyway Right.. Nobody Takes Bad Engine To Trail Run.. Unless They Like Getting Stranded With Blown Engine..
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post #4 of 4 Old 01-25-2006, 11:19 PM Thread Starter
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1978 CJ5 
Join Date: May 2005
Location: NEPA
Posts: 1,237
No oil in the Rad, no coolant in the oil. I havent run the engine enough to confirm tailpipe smoke, I just fixed an unforseen battery charging problem. Tomarrow I'm hoping to check the plugs and compression. It does run well enough to drive around, just a little miss. THe rear main appears to be shot, so that accounts for a lot of the oil. I'm hoping to find 6 good cylinders tomarrow, and then dig into the ignition.

'00 XJ Classic > Stock DD
'88 Grand Waggy - Bone stock pseudo-barnfind
'78 CJ5 - Under minor rehab
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