ISX Oil Pressure Problem

[United340]

Good morning everyone ,

I have a Cummins 870 I rebuild . I’m a former freightliner tech with Cummins certifications from 2010.

I just did a 870 rebuild
About 6 months ago… using {non-oem} parts.

I torque everything to spec n replace everything from rockers , cams , lower bearing , oil pump , cooler n etc.

Customer complain the unit oil pressure would
Drop sometimes from 45-47 to about 25-22 while driving for about 3-4 secs n spike back up..

I personally drive it n it does that . and sometimes does it when u release the throttle pedal ..

I match this issue with a mechanical gauge as well I had plum in by the Oil
Presssure inlet at the oil cooler , the fitting before the Oil filter … it did the same …

Would suspect it to be a oil
Pump problem?

I drain the oil and drip the pan and inspected the pick up tube and the o ring and it was good.. Didt had no metal or heat marks at any of the mains or rods

[marek4792]

Aftermarket parts to rebuild an engine is strongly discouraged just for this reason.. Definitely would suspect the oil pump especially if it's aftermarket too, check the lash and shim the new one.. Also put OEM rods and mains in it so atleast the guy can make enough to rebuild it again with OEM parts when it eventually fails..

[United340]

(07-15-2024 )marek4792 Wrote:  Aftermarket parts to rebuild an engine is strongly discouraged just for this reason.. Definitely would suspect the oil pump especially if it's aftermarket too, check the lash and shim the new one.. Also put OEM rods and mains in it so atleast the guy can make enough to rebuild it again with OEM parts when it eventually fails..

Thank you.. I really don’t like using it but that’s what they provided. I check oil pressure at the oil cooler before the oil filter and after n still the same .. I went on a road test with the gauge at the fitting before the oil filter n it still had the pressure drop some times . So I suspected a oil pump due to where I check the pressure at

[United340]

I check the pressure here road test… when I start the unit cold on the gauge I would read 45 psi at e and about 50-54 when I rev it .. when it gets hot it’s goes down to 20-25 at idle and 40-45 while full rev..

[United340]

I check the pressure here road test… when I start the unit cold on the gauge I would read 45 psi at e and about 50-54 when I rev it .. when it gets hot it’s goes down to 20-25 at idle and 40-45 while full rev..

[Rawze]

(07-15-2024 )United340 Wrote:  I check the pressure here road test… when I start the unit cold on the gauge I would read 45 psi at e and about 50-54 when I rev it .. when it gets hot it’s goes down to 20-25 at idle and 40-45 while full rev..

Once the oil is warmed up, 20-25 at idle is perfectly normal.

running down the roads, anything between 34-44 is about right too.

What exactly are you complaining about?. Is the oil pressure falling below 34~ish while the engine is above 1,000 rpm?. If so then its likely a bad rod/main bearing (wrong clearance), or the oil pump itself. Could also be the pickup tube sicking air.

Did anyone bother to plastigauge the rod and main bearings during the install process to verify all clearances?... this needs to be done any time you use non-oem parts.... and the answer is usually, ;likely not. did anyone bother to verify all the part#'s of each bearing shell individual as they came out of it?... because there is 15% chance that one lobe might have an alternate size bearing when it was built (its random) that is not in the book spec, as it came down the assembly line. this effects oil pressures directly, and eventually leads to a snapped crank/ruined block.



and yeah... that thing is not worth 3 cents with after-garbage trash-can parts in it. ISX's with aftermarket kits don't last very long, have oil pressure issues, and end up needing an inframe in half the time or less again.. and its a total waste of everyones time and moneys.

Next time some moron tells you to use anything but all 100% oem parts, including oem head ..... do yourself a favor and RUN THEM OFF!.

lastly..throw those useless cummins certs in the trash can ... ISX's are finicky beasts and if things are not done 100% right.. it will not last any ways. Here is how it should have been built...
ref: https://rawze.com/forums/showthread.php?...6#pid70606