Alright so I might have done something really stupid. I put 2 bottles of the amsoil engine flush in my engine and ran it for an hour on high idle. I did this when I was checking/charging my AC system. I know that you are only supposed to do it for 15 minutes but the only thing in the amsoil engine flush is just detergents, no solvents so I thought it wouldn't hurt anything. After the flush I changed the oil with fresh 15w-40 and a new oil filter. So afterwards I noticed that when I was driving on the freeway @ 65mph, my oil pressure sat at 49-50psi. It would normally sit around 54-56psi but it seems that something changed. I'm around ~1840 rpms when the speed is 65mph. I changed the oil and filter around 3000 miles to see if the pressure would change but it did not. I also changed out the oil pressure regulator(not the oil drain back) and its still exactly the same. When the truck idles it sits around 18-20 when it used to be 20-22. Should I change out the drain back and/or the oil pump? Could it be my bearings that wore down a little? 

Dont read much ito the oil pressure gauge on an 02. Unless you have an odd ball 02 the pressure sensor on it is nothing but a switch. When you start the engine and reach about 6 psi it closes and the ECM takes over based on coolant temp and rpm and sets the pressure gauge reading, not actual oil pressure. The way to be totally sure is to check your sensor, if one wire runs to it is as described above. If it has 3 wires to the sensor then it is an actual pressure sensor and that would be odd.

mine sat around 65 running, after rebuild its at 55-60 running.  you are still in the clear

4 hours ago, dripley said:

Dont read much ito the oil pressure gauge on an 02. Unless you have an odd ball 02 the pressure sensor on it is nothing but a switch. When you start the engine and reach about 6 psi it closes and the ECM takes over based on coolant temp and rpm and sets the pressure gauge reading, not actual oil pressure. The way to be totally sure is to check your sensor, if one wire runs to it is as described above. If it has 3 wires to the sensor then it is an actual pressure sensor and that would be odd.

 

The readings I'm getting are from my aftermarket oil pressure gauge, not from the factory one.

 

2 hours ago, CUMMINSDIESELPWR said:

mine sat around 65 running, after rebuild its at 55-60 running.  you are still in the clear

 

Yea it looks like I'm still good but I'm wondering what might have changed. I sent in an oil analysis so I will see what they say in the next few weeks.

Directions on the bottle are there for a reason. I'd say the cleaner did it's job and removed something. Hopefully nothing important. As long as you have good pressure, I wouldn't worry too much. Keep a close eye on it for awhile to be sure it doesn't keep falling. You should be ok.

11 hours ago, Max Tune said:

Directions on the bottle are there for a reason. I'd say the cleaner did it's job and removed something. Hopefully nothing important. As long as you have good pressure, I wouldn't worry too much. Keep a close eye on it for awhile to be sure it doesn't keep falling. You should be ok.

Yea I'm not too worried about it, just wondering what exactly changed.

minimum...

 

10 psi at idle

30 psi at 2,000 RPM

 

At least my 2002 report true pressure yet. Even can see pressure through @Chris O. CCD network tool. Even checked with a mechanical gauge once awhile back. Like 68 PSI at 2k rpm.

Isn't there an oil screen somewhere on the oil cooler that can be cleaned, maybe clogged up from flushing.

No screens. Oil cooler is just sealed with steel plate with o-rings. You thinking Ford 6.0L which has screens on the high pressure oil sensor.

Maybe I was thinking oil pressure regulator on filter housing. I just remembered someone had pressure issue and it was because of it. Something there can be cleaned.

https://www.google.com/search?q=98-02+5.9+cummins+oil+pressure+reg&tbm=isch&ved=2ahUKEwiruu7Q86zqAhXTRawKHSrPDJAQ2-cCegQIABAC&oq=98-02+5.9+cummins+oil+pressure+reg&gs_lcp=ChJtb2JpbGUtZ3dzLXdpei1pbWcQAzIFCAAQzQI6AggpOgUIIRCrAjoCCAA6BAgAEB46BAgAEBg6BggAEAgQHjoGCAAQBRAeUI8zWIT8B2D-gghoAnAAeACAAaMCiAHOKZIBBjAuMjYuNZgBAKABAQ&sclient=mobile-gws-wiz-img&ei=efP8XuuZCtOLsQWqnrOACQ&bih=560&biw=360&client=ms-android-verizon&prmd=sivn

Nope... I did a oil cooler gasket awhile back and never seen any screen.

The regulator is just a spring loaded piston that purges back pressure to the sump if it over like 80 PSI.

01 FSM 9-292.   I thought it was higher too. 

What if that thing is sticking open a bit bleeding pressure off

Possible maybe but never heard of it. I will say that you most likely going to have to pick up the gasket for the oil cooler from a Cummins dealer. I've had zero luck finding that gasket in normal part stores. Then you could remove the oil filter base and check the valve port. Bit safer working off the truck than dropping possible debris into the oil galley. 

if you remove the oil cooler, expect to do a coolant flush too..  basically gonna drain the block

 

 

gasket set $50 its a split set as the cooler is two parts.

 

https://puredieselpower.com/dodge-products/98-02-5.9l-cummins-diesel-encore-block-oil-cooler-gaskets.html

 

but if you look at parts 3,10,8,4, this is the pressure bypass valve which is accessible without removing the oil cooler.

 

Edited July 4, 20204 yr by CUMMINSDIESELPWR

I got an update, I replaced the oil pressure bypass spring, oil pressure regulator, and my oil pressure has gone up a couple psi. I changed out the regulator first (inside the housing) with no change to pressure. When I changed the bypass (externally on top of housing), it looks like it made a pressure change. It sits around 52 psi @ 65mph with 295/70R17 tires and a 3.54 rear end ~1800rpms. I also had an oil analysis done and everything is looking good in the engine @ 406k!

Edited August 2, 20204 yr by Southpole560

Remember you have oil jets that cool the pistons too could be you flushed some crud out of one and that would explain some of it.

Also might want to check your oil temperature. I used the trans sensor of the Quadzilla in the oil plug on top of the oil filter housing. Hotter the oil thinner it gets. I typically see 168°F to 175°F in engine oil temp. Being your running larger tires and lower gear ratio could add more heat to the oil causing a drop in pressure too. As seen below 105°F daytime temperature.

 

 

245/75 R16 tires making final ratio to the ground 3.69:1 putting my 66 MPH at a perfect 2,000 RPM and 82 MPH at a perfect 2,500 RPM but this drops my engine load considerable, EGT's drop, oil temperature drops, etc. MPG rises. More heat created anywhere is a lost of power into heat. 

Edited August 3, 20204 yr by Mopar1973Man

22 hours ago, Southpole560 said:

I got an update, I replaced the oil pressure bypass spring, oil pressure regulator, and my oil pressure has gone up a couple psi. I changed out the regulator first (inside the housing) with no change to pressure. When I changed the bypass (externally on top of housing), it looks like it made a pressure change. It sits around 52 psi @ 65mph with 295/70R17 tires and a 3.54 rear end ~1800rpms. I also had an oil analysis done and everything is looking good in the engine @ 406k!

52, you are fine. keep driving knowing you have a clean engine :D

13 hours ago, Mopar1973Man said:

Also might want to check your oil temperature. I used the trans sensor of the Quadzilla in the oil plug on top of the oil filter housing. Hotter the oil thinner it gets. I typically see 168°F to 175°F in engine oil temp. Being your running larger tires and lower gear ratio could add more heat to the oil causing a drop in pressure too. As seen below 105°F daytime temperature.

 

 

245/75 R16 tires making final ratio to the ground 3.69:1 putting my 66 MPH at a perfect 2,000 RPM and 82 MPH at a perfect 2,500 RPM but this drops my engine load considerable, EGT's drop, oil temperature drops, etc. MPG rises. More heat created anywhere is a lost of power into heat. 

 

My oil temp generally stays at or around 197°F. I have used 35x12.50, 265/75R17, and 295/70/R17, with little or no change in the temperature. I'm using the genuine adrenaline oil temperature sensor in the head of the oil filter housing. Is this a normal temp it should sit around? Could my oil cooler not be working efficiently?  I'll be switching to 245/70R17 tires here pretty soon.