XJ Oil Pressure Low: Why only the XJ's?

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09-25-2019, 06:16 PM

#61

97grand4.0

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Location: syracuse ny

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Year: 1997

Model: Grand Cherokee (ZJ)

Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims

Quote:

Originally Posted by RocketMouse

Interesting train of thought there... curious as to why I've seen countless XJ's with the factory 195 t-stat always seem to sit at about 208-210 on the gauge then. I even have a brand new high flow rad in mine, just installed it a few weeks ago... the water pump, t-stat and housing little over a year ago. and mine sits right at 208 like clockwork.

Yeah, it's almost like they knew it was an insufficient cooling system to start with. Totally different than the ZJ. I mean you look at it, the clutch fan is MUCH smaller than the ZJ clutch fan, and then the electric fan is set to kick on at what...215 I think? Which almost invites it to run up to 215.
Maybe the thing to do is to normally have both fans on if the main fan isn't big enough, why not put a 200F thermal switch on the electric fan....? Many cars run 2 fans.
And because it's off to one side of the fan shroud, it can only cool one side of the radiator. Pfft! Shisccabob

Last edited by 97grand4.0; 09-25-2019 at 06:20 PM.

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09-25-2019, 06:44 PM

#62

97grand4.0

CF Veteran

Thread Starter

Join Date: Nov 2015

Location: syracuse ny

Posts: 2,800

Likes: 65

Received 179 Likes on 166 Posts

Year: 1997

Model: Grand Cherokee (ZJ)

Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims

Quote:

Originally Posted by 5-Speed

I guess I am one of the few who havent had oil psi problems. My last xj, 165k miles, idled warm @ 30 psi. The one before that, which I rebuilt the engine, idled at the exact same pressure. One was a aw4 one was a ax15. So I am pretty sure it has nothing to do with the trans. Oil temp is more important than coolant temp or trans temp when talking about bearings. Highly doubt it's the lifters either, unless they are bypassing where the plunger meets the body of the lifter. Cam bearings seem to wear out faster than anything.

Hm now this is interesting..I haven't EVER even taken a look under the valve cover on my xj. Its not my DD just my grocery getter. My zj recently had an oiling problem which led to a lifter bypassing ALL the oil pressure to the lifters out one single lifter, shot right up out of the rocker. Ended up being improper preload on the lifters. But I did notice when I fixed it that the pressure dropped, a lot..to about 35 at hot idle from about 43. SO if lifters are pumping out more than they should be, it will surely drop the oil pressure....Hmmmmmm Maybe time to check the preload on them and check them out. They are quiet but that doesn't mean they're working right, the zj was quietly grinding my rockers and valves with no oil!

Last edited by 97grand4.0; 09-26-2019 at 05:43 AM.

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