Power Torque Low Oil Pressure

Long story short but had OEM motor replaced with Power Torque 4.0 from O'Reilly. Shows oil pressure around 10 psi at idle when warm (195-210). Oil sender replaced twice, temp sender replaced, crank, cam, throttle position senders all replaced. No knocking or weird noises. Checked and cleaned all grounds. AUX fan not coming on when desired, after troubleshooting suspect PCM. New radiator and Mech fan shroud.

Ideas Folks?

I'd pull the oil pressure sender and hook up a mechanical pressure gauge. You can likely borrow or rent one. My in dash oil pressure gauge is 10 plus PSI lower than my actually oil pressure.

Giving the year of manufacture can also be helpful, especially when troubleshooting the fan issues.

jrsavage said:

Long story short but had OEM motor replaced with Power Torque 4.0 from O'Reilly. Shows oil pressure around 10 psi at idle when warm (195-210).

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jrsavage said:

Long story short but had OEM motor replaced with Power Torque 4.0 from O'Reilly. Shows oil pressure around 10 psi at idle when warm (195-210). Oil sender replaced twice, temp sender replaced, crank, cam, throttle position senders all replaced. No knocking or weird noises. Checked and cleaned all grounds. AUX fan not coming on when desired, after troubleshooting suspect PCM. New radiator and Me(37 to 75 psi)ch fan shroud.Ideas Folks?

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What's the oil pressure at 1600 RPM, when hot?
You could pick up one of these to verify the pressure.
http://www.harborfreight.com/engine-oil-pressure-test-kit-98949.html

2000 FSM specs
13 psi @idle
37-75 @1600 RPM

I helped a friend put in a rebuilt from ATK long-block that develop low pressure after few thousand miles, 10-psi-idle, 35-psi at freeway speeds. That was a few years ago and it is still running fine.
If after testing, and the pressure is shown to be too low and out of spec, you should call O'Reillys and see how to exercise the warranty, if possible.
Some warranties will even pay for some of the labor to replace a defective rebuilt.

Sorry Guys. I did sort of skip some info there. This is a 2000 Cherokee Sport 4dr, Auto, NP 231 (which needs rebuilding), the aforementioned Power torque 4.0. Oil pressure on dash gauge at 1600 when hot will hover around 20-30 psi. Haven't checked mechanical fan clutch yet but even today mid 90s and high humidity new shroud and radiator are keeping things 210 or below and A/C is working fine. Didn't have the low oil indicator with old engine but so far haven't had a mechanic figure this out. I suspected oil pump in replacement engine but mechanic who did install swears by new pump. After break in and second oil change on this motor I bumped up from 10w30 to 10w40 synthetic to prevent "check gauges" light from coming on. It seems to run OK but gauge is worrisome. Thanks for the feedback. It's much appreciated.

i just put an atk in my 2000 and when shes all heated up it sits on the 10 tick mark as well. cant say i enjoy looking at the gauge that low but it is what it is. mech gauge reads the same.

I plan on doing the same oil type switch as you did once the motor turns over its first 3k. everything i look into states not to switch to syn till after 2.5k. what did u mean by "ok" did it bring the pressure up?

I have the same thing. I put in an ATK engine almost 4 years ago. Dropped down to 10 psi at idle, 40-50 on the highway. Been that way since 2 months after I installed it. Never had any issues. I run 15w-40 all the time. With my luck it's totally bad and wrong, but it doesn't tick or make any noise so I keep running it.

MrAnderson said:

i just put an atk in my 2000 and when shes all heated up it sits on the 10 tick mark as well. cant say i enjoy looking at the gauge that low but it is what it is. mech gauge reads the same.

I plan on doing the same oil type switch as you did once the motor turns over its first 3k. everything i look into states not to switch to syn till after 2.5k. what did u mean by "ok" did it bring the pressure up?

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I was told 500 miles on switching to synthetic. I probably have around 2k on there right now. I do like checking the oil and seeing a clean dipstick though. Yes. Switching to 10/40 Synthetic made a difference and my check gauges light isn't coming on anymore.

SolarBell said:

I have the same thing. I put in an ATK engine almost 4 years ago. Dropped down to 10 psi at idle, 40-50 on the highway. Been that way since 2 months after I installed it. Never had any issues. I run 15w-40 all the time. With my luck it's totally bad and wrong, but it doesn't tick or make any noise so I keep running it.

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Mine hit zero sitting in crappy Austin Texas traffic. That's when I decided to change from 10/30 to 10/40. Keeps it just above 10psi on gauge and my annoying little bell and check gauges light doesn't come on. Just curious but how's your temp read?

Just so you know, the stock gauge will sit at 10 even when the oil pressure is lower, all the way down to about actual pressure of 5 - 6 psi, then drop straight to zero. Normal hot engine temp for me is right around the 200 mark, maybe a little higher. I see the lowest pressure idling one the engine had run long enough to get everything up to engine temp.

The 4.0 likes 40 weight. I happened to be leafing through my 87's manual this weekend, and above 30f the factory recommends 20-40 or 20-50. I use 15-40 Rotella.

GregGA said:

The 4.0 likes 40 weight. I happened to be leafing through my 87's manual this weekend, and above 30f the factory recommends 20-40 or 20-50. I use 15-40 Rotella.

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Hmmm...So I wonder if the remans have older specs and tolerances than the newer builds because mine with the "recommended" 10w-30 was totally in the gutter pressure wise. Maybe I just need to cultivate some sludge buildup

jrsavage said:

Hmmm...So I wonder if the remans have older specs and tolerances than the newer builds because mine with the "recommended" 10w-30 was totally in the gutter pressure wise. Maybe I just need to cultivate some sludge buildup

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I've owned mine since 87. 129,500 miles. Oil pressure at hot idle is 20, 55-60@2800 rpm.
No sludge in this engine