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98 Run Through

B

BigTicket13

NAXJA Forum User
Location
Michigan
Hello NAXJA,

First off i would like to thank all the members I have been an on looker for a long time just reading and trrying to get as much information as possible without posting questions that have been beated to death. Search option is a great feature.

So let me give u guys/gals the run down with my XJ. Just got the vehicle a few months ago in anticipation of turning my lease in and making the XJ my DD.

98 4x4, 4.0 L6, 185k on the clock, auto, 231, 8.25 - with like a daystar 2" kit.

So far i have gone through the basics on the vehicle did the rear diff, front diff, tc, and trans (dropped the pan). Pulled the throttle body cleaned it out as well as the iac and replaced the battery. Yesterday, i pulled off the valve cover and oil pan did the RMS, pan, and oil pump with a melling HV pump. Now the oil pressure stays at a constant 42ish psi regardless under load or idle warm or cold. Used a wix filter and rotella t5 10-30. FYI didnt fix the leak darn adapter seal :doh:.

So question is or input on what else to do or check and in regards to the oil pressure.

Thanks and glad to finally be a member.
 
BigTicket13 said:
No new guy love.
Click to expand...
Welcome.
You received no responses because you have done what you can do pertaining to the oil pressure.
Now, you can go through the brakes, suspension and driveline, there is always something to work on when you own an old Cherokee.
It burns up a lot of my free time.
__________________
 
Well i was going to replace the sending unit as well - mostly for piece of mind and the part is relatively cheap and easily accessible.

Warm would be just operating temp a few mikes round trip the gf house and back so maybe 5-8 miles. I went with the hv pump really just cause of cost effectiveness the oem pump with the new pickup was more then the hv with the pickup. I got a guy that works for me that builds drag motors for aome local race teams and he said it would be beneficial in a motor with higher miles.

I guess ur right i have covered many of my basics in regards to the oil system just was scared/nervous with the psi having no fluctuation. Guess im attributing that to the new pump. You are right though i got a laundry list of new stuff i need to buy or make - front sway bar links broke during pan change, both bushings shot, leafs inverted, shocks seen better days, gear box leaking alittle, and the list goes on.
 
Thats the next step because from everything i read this motor generally fluctuates oil pressure pretty regularly throughout. What are the ill affect if any and cures i may need to look into?
 
I don't know of an engine that doesn't fluctuate oil pressure through the RPM range. At full temp 42 psi is high at idle even with a HV pump. I would say that perhaps the bypass valve in the pump is stuck, but even then with the pressure at idle higher RPMs would show an even higher pressure.

Let us know about what the pressure is with the mechanical gauge. It sounds like a problem with the oil pressure sending unit.
 
What made me ask was that Synthetic oil is very stable and tends to not suffer the affects of thermal breakdown like conventional oil.

I'm not sure if I would expect a huge change this time of year, and honestly wouldn't worry about it.

I doubt there is anything wrong with the pump.
 
WB9YZU said:
I'm not sure if I would expect a huge change this time of year, and honestly wouldn't worry about it.
Click to expand...
After 30 minutes the oil would be up to temp and show a change.
 
Yea I drove it the other day for like twenty miles plus and it was very minimal change in pressure. Still will get a mechanical gauge on it to verify my findings but the gauge showed typical fluctuations prior to the pump install. What are the ill effects to this?
 
So my question is:
If the only change you made was a pump and a new rear main seal...
And the oil pressure is what it should be at spec RPM...
Then who cares if it is above spec at idle?

I see no drawback here.

Some Jeep owners with almost 200k on the clock would give their eye teeth for anything over 15psi at 700rpm. If you have high 30's or low 40's at 700 because you installed a HV pump, then cudos to you.

It will be interesting to see if the mech oil gauge reads much different than the PCM driven one.
And just a note on that. The PCM driven oil pressure gauge does not fluctuate like a regular sensor driven gauge. It's more dampened than that.
 
Last edited:
The point is that something is off and the oil pressure will fluctuate more than that. The stock gauge is slightly dampened, but not to the extent that it won't move but 2 psi.
 
Well i will check it with a real gauge tomorrow night and see what kind of readings i am truely getting. I do agree that a real gauge will give me a more accurate reading but i would hope that the in-dash wouldnt be that far out of whack.

You just hook right into the sending unit?

Its just got 185k on it and i got some slack from the old lady and a few friends about buying auch a high mileage vehicle. I know the motor is tested and true just trying to get it all in best shape i can before turning it into my DD.

New repair on the agenda is the harmonic balancer - have to see if i can find a right up in regards to that - @ work so search time is limited.
 
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