240k 94 4.0L xj oil change concerns
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Newbie
Joined: Mar 2014
Posts: 16
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
Bought ol Betty in Feb with 240 miles on her, she smokes pretty good & did oil change right away cause she sat for a while before I came along (a year?)... anyways, got a little rust in bottom of pan as seen on dipstick, oil almost smells fuel tainted, moisture droplets on dipstick with oil. Coolant stays perfectly full, temp ok.
question1- are these typical symptoms for this milage & worn vomp. rings & valve seats?
Question 2- should I do a full oil change, or do filter & drain 1/2 the pan cold to get debris?, then top off & dump some lucas? Just wary about all tha play in that old 4.0, don't want to kill ol Betty! I know I have the winter on my side to thicken stuff up a little, & lucas, just need her to keep going till I can rebuild her...
thoughts?
question1- are these typical symptoms for this milage & worn vomp. rings & valve seats?
Question 2- should I do a full oil change, or do filter & drain 1/2 the pan cold to get debris?, then top off & dump some lucas? Just wary about all tha play in that old 4.0, don't want to kill ol Betty! I know I have the winter on my side to thicken stuff up a little, & lucas, just need her to keep going till I can rebuild her...
thoughts?
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Newbie
Joined: Mar 2014
Posts: 16
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
I meant "compression rings", & "the" not tha. Saw on another forum about using Delo... had an old rabbit diesel that ran forever on it, can I use it with some lucas & a good filter? Yup another question. Thanx forum guys!
Last edited by AshleyL; Dec 21, 2014 at 04:40 PM.
CF Veteran




Joined: Nov 2010
Posts: 5,841
Likes: 117
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
*I'd perform a couple of oil changes at a reduced mileage interval. Then keep an eye on oil and coolant (which you should also have changed)
*A simple compression test would likely give you more information about what's going on inside of Betty's engine! The compression spec. for the 4.0 engine is 120-150 psi, with no more than a 30 psi variation between cylinders. Many parts stores will rent you a compression tester very inexpensively; call around.
*Also, You might have a faulty (leaky) fuel injector or two that can contribute to fuel in your oil....
*A simple compression test would likely give you more information about what's going on inside of Betty's engine! The compression spec. for the 4.0 engine is 120-150 psi, with no more than a 30 psi variation between cylinders. Many parts stores will rent you a compression tester very inexpensively; call around.
*Also, You might have a faulty (leaky) fuel injector or two that can contribute to fuel in your oil....
Last edited by tjwalker; Dec 19, 2014 at 07:35 PM.
i would not put the lucas in it. maybe buy some cheap 10-40 and filter. throw a quart of tranny oil in and bring up to temp, drain, then put some good oil and good filter in it. as said, a compression test would be good.
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Napa Silver filter, 4 quarts Rotella T3 with 1 quart of Marvel Mystery Oil.
Run it for 1,000 miles.
BTW, have you shone a light into the oil filler hole to assess any sludge build-up?
Run it for 1,000 miles.
BTW, have you shone a light into the oil filler hole to assess any sludge build-up?
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Joined: Mar 2014
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
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Thread Starter
Newbie
Joined: Mar 2014
Posts: 16
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
I know a teardown is in order & I love rebuilding any strait 6, but $$$, need my own shop!
Thanks for all the great tips! I'll let u all know how goes!
CF Veteran




Joined: Nov 2010
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From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
I'm not a fan of ANY additives in the crankcase with the oil. One exception to that would be if I can visually see an engine contaminated with substantial "sludge".
The only thing I generally do is to adjust the OCI (oil change intervals) to less mileage if I feel that the engine has not been maintained properly with reasonable oil changes. These more frequent intervals will safely clean your engine over time.
The only thing I generally do is to adjust the OCI (oil change intervals) to less mileage if I feel that the engine has not been maintained properly with reasonable oil changes. These more frequent intervals will safely clean your engine over time.
Last edited by tjwalker; Dec 22, 2014 at 10:13 AM.
Thread Starter
Newbie
Joined: Mar 2014
Posts: 16
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
I'm not a fan of ANY additives in the crankcase with the oil. One exception to that would be if I can visually see an engine contaminated with substantial "sludge".
The only thing I generally do is to adjust the OCI (oil change intervals) to less mileage if I feel that the engine has not been maintained properly with reasonable oil changes. These more frequent intervals will safely clean your engine over time.
The only thing I generally do is to adjust the OCI (oil change intervals) to less mileage if I feel that the engine has not been maintained properly with reasonable oil changes. These more frequent intervals will safely clean your engine over time.
so I did a high milage oil change w/ marvel, Fram filter, coming up on 600 miles & can still see a lot of crap up top.
she's a little rough, but I'm all about a cast iron long 6, I HATE aluminum engines, that's why I bought her & I know I've got to tear down, looking forward to it.
Thread Starter
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
I thought water too, little drops on the dipstick. She's all cast iron, grimey as hell, rockers tick, & smokes like a train. Don't smell coolant in exhaust, which is grey not blue-ish, gasket maybe? Chances of it being a water jacket in the 4.0? Last straight 6 I worked on was a 1918 International!
Thread Starter
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From: Minnesota
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 HI
Ran ATF in her hot for a few, changed oil @ 570 miles from last change, marvel top off & some in the gas hoping it will clean my injectors a bit... she's a smoking Betty now! Considering sea foam? Little drip from rear seal which has been bulging since I bought her. When I drop the pan to replace the seal is there enough room to grab a connecting rod & give it a jiggle to check for piston slap? Would like to rule that out while it's open? Thoughts?
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