Challenger73

My father is looking at a 2004 Ram 2500 with the 5.9 and 157k miles. He has not owned a diesel before and was a bit worried that the trucks oil pressure dropped to about 20 psi at idle.

Is this something to be concerned about?

Thanks!

wellmax

i do not think so,
i have a 2005, 49K miles and at idle the oil pressure gauge shows low, but as soon as you increase rpm's the oil pressure goes up.

someone on the forum can explain it better, but i do not believe the oil pressure gauge is a direct connection to the motor, but sometype electrical gauge.
direct connection would be best then you would not be concerned.

HGR002

i have an 04 and mine does the samething it sits at right about 20 psi at idle but when i take off it goes back up to normal

sr4440

LOL, where is he reading the pressure at? The factory gauge isn't even close to being correct. It is on a hobbs switch and anything above 6 psi it will read what the customer expects.

here is a quote from the manual
I put a mechanical gauge in and i can say without question, the factory gauge is a bad joke.


Joe

Sur5er

The factory oil gauge is really an idiot light with an arm!

FOXY005

sr4440 just curious what does your mechanical gauge read at idle and lets say at 1800 RPM's with motor at operating temperature of 190* ?

AH64ID

I read my oil psi above the ECM on the drivers side of the block, so its a little lower than those that read at the oil filter.

Idle 20
1100 30
1600 50
1900 + 60-65

These are cruise pressures, towing pressures are 3-5° lower as the oil is hotter.

On a cold motor the oil psi will go to about 85 max.


But a OEM "gauge" that drops to 20 at idle means the software in the ECM is old.

sr4440

same as AH64ID, hot idle is 19-21 @1800 it is around 65


Joe

06RAM2500

Same here

20 at idle
55 cruising
75 cold (outside temp below 40)

cdennyb

Mine's 25 @ 1000 rpm at the oil filter housing Usually runs at or near 60 cruising at 1800 unless hotter than hell-o then is drops to 50.
That truck sounds normal but as you have read so far, the gauge isn't necessarily telling the real truth, but for the most part, it's fine.

papaduck

The oil pressure at idle is good if it is at least 10psi on a hot engine using a real guage. The oil pressure swing on a Cummins diesel engine goes from 15-20 psi to 80 psi. This caused a lot of complaints so I think this is why the stupid computer controlled guage was installed, to stop the complaints from people who did not know.

bigwheels94

When was the change in software made? My 04.5 gauge reads exactly what I expect. Cold idle it reads about 45#, Warm idle it reads about 20#. And any time I'm above idle it reads about 45-50.

AH64ID

There have been many updates over the years, but rest assured its 100% fake readings.

papaduck

bigwheels94

Don't know about the software but the in dash guage is not a real guage. As long as you have 6 psi at the switch the computer will control the guage and simulate what a real guage should be reading.

I have installed a real guage and most of the time the two guages are close togather, however there are times that they are a long way apart. The equipment I drive at work also uses the Cummins 5.9. I saved an engine because it had a real guage and I noticed that the oil pressure was falling below what was normal. Took it to maintenance and found the crankcase was full of fuel.

I will never trust the indash guage!!!!!!!!! To not have a real oil pressure guage can cost you an engine!!!!!!!

AH64ID

Mine is only "accurate" at 1200-1300 rpms on a warm motor the rest of the time is 10-40 psi off.