KJ oil pressure?

[SDLiberty]

Ok so i finally installed my Auto Meter oil pressure and Voltage gauges. Now i notice something that i don't know if i should be alarmed about? Per specifications, I know the MINIMUM oil pressure is 4 psi and there is a rather LARGE window at 3000 RPMs. 25-110 psi :shock: Now here is what my KJ is at. At normal operating temp @ 600 RPMs Please note that i did an oil change at the same time of install w/ full synthetic 5w 30. Should i worrie? At 2100 Rpms or so it will climb to about 75-80psi as well. Sorry for the crappy picture, but you get the idea. Oh its a 2004 3.7L

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[flair1111]

just a guess, but i think thats a good thing.the higher the better.

 

[moparman]

What you have is good. A sign of good clearances, I believe.

 

[SDLiberty]

OK so does anyone know for sure!? What our KJs are really suppose to idle and operate at? Lets face it.... And uneducated guess for something like this could be a HUGE problem down the road. If i wanted a guess i could have gone to Pep boys. hahaha

 

[k99jk99j]

according to my service manual hot idle is 8 psi.

 

[Idaho08KK]

25psi at idle is nothing to worry about. That is a good thing. 75-80 psi at 2100 rpms is also normal.

 

[kb0nly]

You got fresh oil in there, and you didn't say how many miles on the motor, but sounds to me like your doing mighty fine!

Seems like our minivan we used to have always had higher oil pressure for a few weeks after a change and then it would come down a bit but still higher than the minimums that the service manual showed.

The service manual does show hot idle at 8 psi as others posted, but is that the minimum requirement? Usually service manuals state the minimum or maximum at which the motor can still operate. As long as you don't go below or above your fine. I think the manual also states a range of allowed pressure due to the fact that you might be running one of a couple different recommended oils, and some say there is also a difference between dino oil, synthetic blend, and full synthetic. I haven't tested that myself so i can't comment fully other than what i have read online.

 

[SDLiberty]

So now with that said and you know what i'm running at operating temp/idle.... Here is a pic when i started the KJ this morning/ cold temps

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Just seems to me i'm gonna blow the seals out of it??? Runs GREAT though.
BTW i have 80,500 miles on it.

 

[kb0nly]

Seems normal... I remember this past winter i went out and started the van one morning and the oil pressure gauge maxed out for a few minutes until the oil got circulated and warmed up.

If it hasn't blown the seals in 80k i doubt it will now!

 

[ridenby]

I think your lib.has great oil press.,where did you tap into system? that is a wet gauge?

 

[moparman]

I wasn't guessing. And too high oil pressure will blow an oil filter first. The Jeep oil pressure specs are low because with the sloppy tolerances of a mass produced engine and today's thin oils, it COULD be that low. Also it takes HP to have oil pressure, if it was on the low side, there would be less drag in the engine. Which would be more favorable for emissions and MPG. But the oil pressure is the cushion that is keeping your engine together. It is the crankshaft condition, bearing clearances and oil pump condition that determine how much oil pressure you will have.

The oil pressure you have is what any engine builder desires to have. Yet if it was lower, the engine would still run. Drive a Jeep for 80,000 miles, put a gauge in it (is it accurate, really?) and then you have a problem? If anything the oil pressure was higher when the engine was new.

 

[SDLiberty]

I wasn't guessing. And too high oil pressure will blow an oil filter first. The Jeep oil pressure specs are low because with the sloppy tolerances of a mass produced engine and today's thin oils, it COULD be that low. Also it takes HP to have oil pressure, if it was on the low side, there would be less drag in the engine. Which would be more favorable for emissions and MPG. But the oil pressure is the cushion that is keeping your engine together. It is the crankshaft condition, bearing clearances and oil pump condition that determine how much oil pressure you will have.

The oil pressure you have is what any engine builder desires to have. Yet if it was lower, the engine would still run. Drive a Jeep for 80,000 miles, put a gauge in it (is it accurate, really?) and then you have a problem? If anything the oil pressure was higher when the engine was new.

Yeah i guess if it was to hi i would have problems keeping an oil filter on it. I did buy Auto Meter gauges for a reason. The gauge i have is an electric gauge. Your absolutely right... It could be the gauge... Will check this out for sure! Should i i do a write up on this for those that would like to do this???

 

[kb0nly]

Yeah i guess if it was to hi i would have problems keeping an oil filter on it. I did buy Auto Meter gauges for a reason. The gauge i have is an electric gauge. Your absolutely right... It could be the gauge... Will check this out for sure! Should i i do a write up on this for those that would like to do this???

Please share!!

I would like to know where you tapped in the sensor for it, what you used for a guage pod, the works!!

 

[ridenby]

Yes, please,I would like to know how you did this.Thanks

 

[SDLiberty]

I'll take some pictures and type up a how-to for those that want it.

 

[moparman]

Yeah i guess if it was to hi i would have problems keeping an oil filter on it. I did buy Auto Meter gauges for a reason. The gauge i have is an electric gauge. Your absolutely right... It could be the gauge... Will check this out for sure! Should i i do a write up on this for those that would like to do this???

Electric gauge? I would only hope that it is consistent, not necessarily accurate. I would also think that Auto Meter makes good gauges. The best thing would be a mechanical gauge. But at the same time, you should be happy to have that oil pressure, not complain about it.

I was more hands on with engines in drag cars in the late 70s and early 80s. When we did engines back then, we wanted at least 30 psi oil pressure at an idle and 70-80 when the RPMs were up. Sometimes it would go to 100 psi cold with 40w oil. Oil seals will not blow because they are in "splash" areas that are not pressurized. The oil filter is under pressure, that is why it is such an important check after doing an oil change. Basically only some of the smaller oil passages, crank journals, lifter bores and maybe the rocker arm shaft are pressurized. The oil drains back down to the pan by gravity.

Single digit oil pressure at an idle with 5w30 or 0w20 oil (thin oils=camel piss) just scares an old school guy like me. But today's high temp emissions motors changed the rules. I have been driving late model cars long enough and used the proper oils so I trust the thin oils.

One of the funnier (now) low oil pressure problems I had was when the pushrods were falling out of my big block Cuda. I put them back in only to have it blow up about 10 days later.

 

[tjkj2002]

Electric gauges are notoriously famous for being very inaccurate.The only way to know the actual PSI is by a quality and calibrated gauge,99% of automotive gauges on the market are not accurate(even the mechanical gauges).Plus with the pickup so close to the oil pump you get a false reading anyways since that 25psi at warm idle is what's coming from the pump and not what the entire engine is seeing.

 

[SDLiberty]

Would the oil filter have anything to do with the pressure? I used a Purolator oil filter. When i changed the oil i used Castol edge 5w 30. I have read that it could be a crappy filter and cause it to be hi. I also noticed today while driving it in the WARM UP phase. I come really close to 100 psi REALLY!!!! Then drops down to 75 or so at a stop light. Once its warm, idle at 25psi. Back up to 75+ on the highway. Looking at getting a mechanical oil pressure test gauge to maybe get a exact reading.
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[tjkj2002]

Would the oil filter have anything to do with the pressure? I used a Purolator oil filter. When i changed the oil i used Castol edge 5w 30. I have read that it could be a crappy filter and cause it to be hi. I also noticed today while driving it in the WARM UP phase. I come really close to 100 psi REALLY!!!! Then drops down to 75 or so at a stop light. Once its warm, idle at 25psi. Back up to 75+ on the highway. Looking at getting a mechanical oil pressure test gauge to maybe get a exact reading.
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Your fine,Purolator filters are some of the best out there.Just remember the min specs are bare min and most likely only found on very high mileage engines with little to no maintenance.Just remember you also have a SOHC engine and with the cams on top of the cylinder head more oil pressure is need to keep those bearing lubed since by the time the oil get's up there it may be at 1/3 or less what it is at the oil filter.You do not need as much oil pressure in a OHV engine sine the cam is closer to the crank(and oil pump) so it get's plenty of oil pressure with less overall oil pressure at a gauge.Besides the crankshaft,camshaft,and lifters everything else in the engine is lubed by oil splash.

 

[Prospect62]

I'm also interested to see what you tapped to get an oil pressure reading. When's the write-up coming?