3116 Oil Pressure Help

[YOUNG GUN]

The oil pressure gauge typically reads 35; I've noticed lately that sometimes at idle it drops half way between 0 and 30, but right when RPM goes back up so does the pressure gauge.
I recently replaced the engine oil and filter and I check the level once a week and it's perfect, so it's not oil level.
Engine temp usually runs about 160.
I've read the TM on gauge/sending unit troubleshooting and I will do that tomorrow.

Other than troubleshooting the gauge and sending unit, does anyone have any other thoughts or advise?
Oil pump issue?
Anyone experienced this issue before?

Thanks in advance for any help!

 

[AceHigh]

I think what you described is normal. At idle it can go to 15 when hot, right? Am I missing something?

 

[rlwm211]

If you are worried about oil pressure buy a mechanical gauge and install it and see what it actually is. That is the only sure way to know the oil pressure of your engine.

While the electrical gauges are almost always accurate, sometimes they are not.

Why risk a huge expense such as an engine by not being sure of the oil pressure?

Chances are everything is normal, but it only takes a few minutes and about 25$ to know for sure.

RL

 

[jaymcb]

FWIW, after a long run, my 3116's gauge drops a bit below the 35PSI mark too. I think it's pretty normal.

 

[CatMan]

3116 Cat Oil Pressure in A3

The Cat 3116 engine has a gear driven gear type oil pump at the front of the engine. It operates in direct proportion to engine RPM. A lower oil pressure reading is at low engine RPM is normal. No problem since there is low load at Idle RPM. The high pressure reading is controlled by the oil pump bypass valve that opens when the pressure reaches maximium. The oil is redirected back into the inlet side of the oil pump.

A Cat manual will tell you this. The Military -10 operators manual does not.

Cat Man

 

[spicergear]

My 1160 V8 CAT will idle 60psi cold and 15 to 20psi hot.

Also, engine rule of thumb is 10psi per 1,000rpm. So if you're idling at 700rpm with 15psi, you're still in clear from the engine builders stand points.

 

[YOUNG GUN]

Thanks for all the advise everyone, it seems that it may be normal?
I watched very closely this morning on my way to work, so let me describe the actual conditions.

-34F this morning
-started right up
-oil pressure started at 60 and slowly dropped down to 30-35 as the engine temp came up while driving
-after engine was at operating temp, the pressure was at 30-35 while driving and while at idle it was slightly below the halfway point between 0 and 30 so maybe 10.
-also, I don't think that its ever gone above maybe 40 or so even at high RPM

If anyone has any additional thoughts from this more detailed description, let me know.

I should've had more detailed information about this in my original post, so sorry for that; I'm new enough to diesel engines and MV's that I really rack my brain on any issues/concerns that I have, and end up posting bofore I have all the details straight.

Thanks again for all your help!

 

[AceHigh]

The 10 psi is lower than I have seen but the rest is similar to mine. How is your oil? If you have too much oil, you may have diesel mixed in with it and that will give you a lower reading. I would get the mechanical gauge as a backup.

 

[shovelheadmike]

If you do install a mechanical guage, be shure to use copper tubing and not the plastic tubing as it will likely fail after a year or two.

 

[YOUNG GUN]

It sounds like I should hook up a mechanical guage just to be on the safe side.
The oil level is perfect, and I check it at least once a week.

 

[YOUNG GUN]

Thanks again for all your help!

 

[goodguyzy]

mine seems to idle at 30 and 60 drive. i would be a little worried about that 10-15 something seems funny about that.

 

[YOUNG GUN]

LONG overdue update:
Finally got around to testing with a mechanical gauge; water temp @ 160F it idles at 40 PSI, and at high RPM's (apx. 2,600) it's at about 70 PSI.
I got a new sending unit on order, and the trucks running great.

 

[Krink545]

Thats good to hear.
I need to put a mechanical gauge on my M923 with the 250 Cummins. It reads about the same as yours. I hope its just a sending unit or gauge.

 

[YOUNG GUN]

Idles at 10-15 and higher RPM's at 30-35?
The manual for the A3 states 35-75 PSI is normal.
What is it for the M923?

 

[Monkeyboyarmy]

subscribed

My A3 does the same thing. Guess I'll try the mechanical gauge too.

 

[YOUNG GUN]

I got my new oil pressure sending unit yesterday from Erik's, and installed it this morning.

Problem solved.

 

[buddy_holly]

Could a bad rear main seal cause low oil pressure? I'm trying to put the puzzle pieces together. My oil pressure gauge has always read low but it would move according to RPM. Recently though it sits at almost nothing, topping out around 10-15 psi when I'm up to road speed. I also have a leak I haven't been able to determine yet and it seems to be coming from right around the bell housing. The curious thing is that I always check the engine oil and the gearboxes; everything is perfect. I'm worried and hoping it's not what I'm afraid it is. Thoughts?

 

[YOUNG GUN]

My advise would be to go buy a $20 mechanical gauge from the auto parts store and hook it up.
This is what I did and determined that my oil pressure was fine, then replaced my sending unit.
Problem solved.
Hope this helps.

 

[goodguyzy]

There is no way a leak would affect the gauge unless it was a major leak, my guess is the sending unit also.