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What's your oil pressure?

W

wildman

NAXJA Forum User
Location
Jennings, LA
I've been wondering what the oil pressure is supposed to be on my Cherokee. '89 4x4, 4.0L I6 moter. Here are my readings, all on a warm engine. Idle-Park = 38-45(same through to about 1000rpm). 1500rpm(approx. 55mph) = at or around 60. 2000rpm(approx. 70-75mph) = at or around 73. These are my figures, just wondering what everyone else's is/what it supposed to be. Thanks ya'll!
 
mines about the same. Usually on the high side a little more.
 
if your wondering if your pressure is good, its fine. i wouldn't worry about it until you see it drop to around 20at idle warm, or worse 20 at cruise speed.
 
wildman said:
I've been wondering what the oil pressure is supposed to be on my Cherokee. '89 4x4, 4.0L I6 moter. Here are my readings, all on a warm engine. Idle-Park = 38-45(same through to about 1000rpm). 1500rpm(approx. 55mph) = at or around 60. 2000rpm(approx. 70-75mph) = at or around 73. These are my figures, just wondering what everyone else's is/what it supposed to be. Thanks ya'll!
Click to expand...
mine's the same too.....it's good
 
jeepkid2000 said:
if your wondering if your pressure is good, its fine. i wouldn't worry about it until you see it drop to around 20at idle warm, or worse 20 at cruise speed.
Click to expand...

Mine has just started to drop around 20ish at idle once I've driven for 20-30 minutes. Have any idea what might be causing that, and how to fix it?
 
With a freshly rebuilt stroker:

45 highway
20-25 warm idle

Doesn't this depend a lot on what weight oil you are running?
was at 20/50
now at 5/20 with a quart of 10/40
 
idle = 10-15
any throttle 20-25

240 k miles, factory motor from valve cove to oil pan.
 
220K on my 93. 35-40@idle 55+@1800rpm.
Hasn't been rebuilt as far as I know.
Mobil1 10W30 and K&N Gold Oil Filter.
 
Not sure about ur low pressures(low in comparison to mine). I have 108k miles on my '89. I used castrol syntec blend on all my oil changes every 3k miles on the mile or close 2 it. 10w-30. I have quite a few friends with XJ's of various years and mileage counts and most of them use a different weight oil. Their pressures are all about the same as mine. As far as I understand, a pressure below 28 or so ad warm idle could mean a problem(i'm guessing maybe the oil pump?) and i'm pretty sure something off the meter on the high end could probly be a problem too ;).
 
jeepkid2000 said:
i wouldn't worry about it until you see it drop to around 20at idle warm
Click to expand...

'89, 280K miles, no engine work, 10-30 Penzoil with FRAM filter (amazing she has made it this far, isn't it?)

45 cold idle
42 cruising around 65mph
20 warm idle (I guess I need to start worrying, but worry about what??)
 
'01 about 150K miles... up until last october at idle in a warm engine i was getting 20ish and at hiway speed 40-45... since october it pegs out at startup... once warm idle is about 45 and at speed 60-70...

i was worried about the jump in pressure but it seems normal when compared to most everyone else...

on our newest, a '99 the thing just sticks on 80 and never moves... figure its the sensor (?) and will replace it soon...
 
Factory spec is 13 psi warm idle---you guys with idles psi's in the 30's, how long has your engine been running when you look? Sounds like it hasn't warmed up yet. And yes, the thicker the oil the higher the resultant pressure.
 
2001, I6 with 15k - 50psi at cruising. Using Castrol GTX 10w30 and a larger Purolator Pur 1.
 
Think of the engine's oil pressure in the same terms as a human being's blood pressure.
Too low a pressure is bad; not enough oxygen reaches the brain of a human being and he faints, not enough oil reaches the bearings in the engine and it eventually fails.
Too high a pressure is also bad; a human being has a higher risk of a heart attack or a stroke, while an engine with too high an oil pressure can blow its seals and rapidly wear out the oil pump.
What's a normal oil pressure? Anything below 13psi hot idle and 37psi at speed is definitely not good. Anything above 75psi at speed also isn't good. The oil pressure sending units are notorious for giving false readings so don't rely on the absolute numbers. If the gauge is within the normal range, just be happy with that. A lighter weight oil will yield a lower oil pressure but it'll also flow faster to the moving parts especially when cold.
 
Dr. Dyno said:
Anything below 13psi hot idle and 37psi at speed is definitely not good.
Click to expand...
Good to hear. That tells me my 4.0L (20 hot idle, 42 at speed) has a bit of life left. Thanks for feedback.

-Maz
 
I was a little spooked at mine till I read 13 psi at idle.

When I was running 5-30w all winter it idled well above 20 psi.
Now that I changed to 10-40w for the summer its been idling below 20 psi.

kinda makes me wonder if I need to have the pickup screen cleaned or something. Not something I want to do if I can help it.
 
Before I found this forum I thought mine was too low. Other concerns were cooling ('90) and 147K miles.

I took the head in to get cleaned up and the guy asked if I was going to keep it or sell it. I asked why. He said the carbon build up indicated that the rings were on the verge of failure. Well who wants to get rid of their one and only XJ! I pulled the pistons, saw the x-hatch on the walls, broke the glaze, put cast rings in, replaced the con rod bearings put it all back together.

Result? Oil pressure came up to like new readings 60/80 for a few months. Now it is settled down a little to 40/55 after 60K miles. I really should have done the mains but I didn't. I feel guilty about it enought that I will probably do it when replacing the rear seal and to seal up the pan.
Oh yeah, my cooling problem was resolved! I had done everything but convert to open system. Now it runs just fine.

My 92 never goes above 40 with 199,845 miles and my 97 GC never goes above 60 with 95K.
 
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