New Cast Iron Oil Pump pressure low

[hookliftpete]

This must be something that is particular to the isx engine, my isc will be at nearly 70 psi on cold start, settles around 60psi at 18-1900, idle somewhere around 35ish.

[Waterloo]

Having been inside the motor, I can see 80psi doing damage, especially as was mentioned on the front cover. The ISX is loaded with those silicone string gaskets, and it would not take much to blow those apart and have oil and coolant going everywhere.

[Rawze]

(12-06-2020 )smorgan87 Wrote:  RAWZE can you shed some light on why cummins engineers hate oil pressure? Is it really true more than about 50psi will not only do all of what you said but also wash out bearings? Why does a cat run 60ish forever and cummins will self destruct over 50ish? Also im assuming that my reman 2350 has an old style pump if im runnin 42 at speed?

(speculation here)...

As far as washing out bearings due to oil sneaking in behind them at higher pressures, and the engine maker reducing pressures partly due to this, I have never found any official documentation as such. It is speculation based on some cummins ppl saying this in the past a long time ago. This would depend heavily on how much retaining lip there is at the edge of the bearings to hold them in place vs allowable wear. Some engine makers have a narrow lip/catch to prevent bearing spin, some have a larger ones.

Also, Waterloo is right ... A lot of gaskets like the front gear train gasket would do well to hold up to 60 psi from all appearances without some help and it is already well known that the rear bell-housing gasket likes to leak when the engine is driven really hard/abused already. higher oil pressures would only make this worse I think.

I know that an engine with an overall lower pressure design will generally have lower oil temps and therefore need less oil cooling. A lot of this is due to less pressure at the oil pumps ball-spring regulator, which produces resistance heat in the oil.

Ball-spring regulators are notorious for causing oil temps to rise, they are a constant source of efficiency loss, and are prone to cavitation. The lower pressures that you can keep this type of oil pressure regulator, the better off it becomes. There are better designs for pressure regulators because of this very reason. A bypass-charging valve type regulator does not have these issues, but they are more complex and wear out quicker.


The lower oil pressures in an engine also benefit the engine through fuel efficiency combined with a more rounded range of operation. - I can only speculate why the red engine maker did what they did, but i would suspect these traits that I just mentioned are some of what was likely saugh after. The engine is above the minimum rating of 10 psi for every 1,000 rpm rule, so 20 psi at idle under no load is double this rating and at 40 psi, this would be tolerant to 4,000 rpm. - if anything could be guessed towards the pressure rating it is designed to run it, one can only speculate that it looks like they took the minimum oil pressure rating requirements for good diesel engine design and simply doubled them, but did not go higher ... maybe kept it to a minimum to improve efficiency? - and improve flow during cold start? reduced pressure and higher volume at the bottom of the pistons to reduce oil consumption and increase cooling effect?, lower overall oil cooling requirements>? etc..

[Mandy0917]

So I took off the oil pan today and found a dime laying on the entrance to the center of the pump , if it was already there or fell off after I took of the spring, I’m not sure, remember I did put the dimes with the pump already installed and is harder to put the dimes in place than with the pump off, so what I did is to put 2 5 cents coins that equals 3 dimes in thickness and put everything back , now I’m getting a little better pressure than the old pump was doing, but I was conservative on the amount of coins because I had such a high pressure yesterday that I didn’t want to have to take off the oil pan a third time. The 5 cents coins also fits better on my opinion regarding the diameter and have less chances of moving around. I did get 35psi with engine cold, and then drive the truck around and did get up to 41 at 1500 rpms, I wish I had put another coin and I would be at 45 or 46, but for now will leave it like that, that’s already a victory over the new oil pump version. I’ll share a couple of pictures so you guys can see the little difference on the pump

[Mandy0917]

(12-06-2020 )Mandy0917 Wrote:  So I took off the oil pan today and found a dime laying on the entrance to the center of the pump , if it was already there or fell off after I took of the spring, I’m not sure, remember I did put the dimes with the pump already installed and is harder to put the dimes in place than with the pump off, so what I did is to put 2 5 cents coins that equals 3 dimes in thickness and put everything back , now I’m getting a little better pressure than the old pump was doing, but I was conservative on the amount of coins because I had such a high pressure yesterday that I didn’t want to have to take off the oil pan a third time. The 5 cents coins also fits better on my opinion regarding the diameter and have less chances of moving around. I did get 35psi with engine cold, and then drive the truck around and did get up to 41 at 1500 rpms, I wish I had put another coin and I would be at 45 or 46, but for now will leave it like that, that’s already a victory over the new oil pump version. I’ll share a couple of pictures so you guys can see the little difference on the pump

[marek4792]

Good to see that 3 dimes or 2 nickels in your case was the charm! Looks like we may have cracked the the low pressure issue with the new pumps, definitely keep us posted!

[alamow]

Mandy, thanks so much for posting. Information like this is gold dust. Much appreciated.

Cummins put my truck on the dyno. 520hp at the wheels. 35psi at rated HP. So I have an operational engine brake at 2050rpm..... within spec according to Cummins.

I'll try 5mm shim when the Xmas rush stops.

[JimT]

I can't speak for others, but my new oil pump, installed September this year, produces 25psi at idle (720rpm), about 36psi at 1500rpm and around 38-39psi at 1800-1900rpm.

One additional thing I did during my rebuild was to replace my oil cooler. Not sure if that had an effect on oil pressures, but I can say that my cold start oil pressures are now much lower then before the rebuild. Prior to rebuild I would have 40-ish psi at cold start idle with up to 55-60psi if I tried to drive before the oil warmed up (150F on the coolant temp). Now with the new pump I'll start out around 30-35psi at cold start at idle with a jump to maybe 40-45psi at 1500 rpm while cold. Oil pressure also normalizes much sooner without engine coolant temps needing to hit 150F.

edit: Cold starts/cold oil includes ambient temps ranging from 70F down to 25F. There has been no real difference in oil pressures due to the seasonal drop in ambient outside temps

I didn't shim anything on my pump.

Only thing I really don't like is the gear noise from this newer pump. Depending where you stand (especially toward the rear of the tractor) the noise from the pump can actually be louder then the engine. It did get quieter as the first oil got older, but once I changed it the noise got loud again. This oil hasn't yielded any noise reduction with age and it's almost time for another change. Hopefully the addition of gear lube with the next oil will help a little bit. And yes, the noise from the pump is always louder when the oil is colder, but not a massive difference.

[VNL64T]

Hi all.
Reduce noise ..
Do not place gaskets underneath the pump to the engine block ...
Use Loctite 518

"New pump does not use shims to set gear lash."
"Lubricating oil pumps with threaded regulator plugs do not use shims to adjust gear lash."

mm in
0.08 MIN 0.003
0.57 MAX 0.022

Be sure to check the gear clearance !!

I installed without gaskets using Loctite 518, the noise disappeared ..