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Unread 02-07-2014, 08:43 AM   #1
Harbison
Registered User
1990 FSJ Wagoneer 
 
Join Date: Feb 2013
Location: Shallowater, TX
Posts: 8
Is it time for engine rebuild?

My 1990 GW has 184K. Engine runs strong. Oil pressure at 40. But has a lot of back pressure and spits oil out the tube into air filter. Looks like an oil bath filter! Loses 2-3 quarts per week. Doesn't burn oil. No smoke. Just spits it out. Using 10W40. Never been abused. Never off-road. Original owner was college professor who drove it to work for 15 years and put 150K on it. I've had it last since 2005 and put rest of the miles on it. Rebuilt transmission last year.
Is it time to rebuild? If so how hard are these engines to rebuild? Your experience and advice is appreciated!

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Unread 02-07-2014, 09:54 AM   #2
muddy93
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1987 FSJ Wagoneer 
 
Join Date: Aug 2007
Location: Templeton, Indiana
Posts: 1,906
sounds to me like your PCV system is not working at all. Replace the PCV valve and check the condition of all associated hoses.

Doing compression tests (both wed and dry) will do more to tell you the condition of the engine, and weather or not you need a rebuild.


Also, what exactly do you mean by "But has a lot of back pressure......"? Usually the term "back pressure" refers to the exhaust. If you really do have to much back pressue, it's possible that your cat converter could be clogging.
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Unread 02-07-2014, 09:57 AM   #3
super98lsc
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1999 WJ 
 
Join Date: May 2006
Location: Austin, TX
Posts: 1,397
By back pressure do you mean blow by? For example if you pull the oil filler cap is it puffing smoke out the tube when running and puff even more when you rev it up? If yes likely the cast piston rings are worn out. You may also want to ensure the PCV circuit off the back of the carb to the manifold is working correctly and the passages in the intake are clean and clear. Then replace the breather cap aka oil filler cap which has the oil separator built into it/baffle which is designed to prevent the oil from spewing up into the air cleaner assembly. Lastly a good seafoam of the top end and some marvel mystery oil to de gunk the engine internals might go a long way.

By 160k on my 90 my valve seals were done and the rings were weak and compression was down and had a little blow by but not ever enough to add oil and zero smoke out the pipes.
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Unread 02-07-2014, 07:36 PM   #4
Harbison
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1990 FSJ Wagoneer 
 
Join Date: Feb 2013
Location: Shallowater, TX
Posts: 8
Thanks for the advice. I'll do some more checking. Also I replaced the catalytic converter a year ago. Doesn't puff smoke, just fills air cleaner with oil.
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Unread 02-09-2014, 08:26 AM   #5
super98lsc
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1999 WJ 
 
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Location: Austin, TX
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Quote:
Originally Posted by Harbison
Thanks for the advice. I'll do some more checking. Also I replaced the catalytic converter a year ago. Doesn't puff smoke, just fills air cleaner with oil.

Check and clean the PCV system out and install a new PCV valve sounds like you have a blocked up crank case which is forcing oil back up the fill tube to the top into the breather filter (yellow oil cap) through the hose and draining into the air cleaner housing. Also make certain those PCV vacuum lines are connected to the correct place in carb and manifold. "Sometime previous owners like to try their hands at automotive engineering"
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77-Corvette Stingray 496 BBC/TH400 built 667hp+
===================================
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!
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