Oil pressure issue

dieselracer07

dieselracer07

New member
Joined
Dec 20, 2008
Messages
3,968
Now for another aggravating issue with my truck.... This engine has less than 2500 miles since a complete rebuild. Once it is at operating temp it will occasionally drop oil pressure. It only happens once coming to a stop or putting it into reverse and doesn't do it 100% of the time. It instantly rises back up if you give it some rpm. Oil has been changed 3 times since the rebuild and has always looked great, I'm running Mobil One 15W40 with Hamilton Zinc additive, Wix filters, and the sending unit is new. I've set my idle fairly high to help with the issue some (900-1000rpm). When cold I have 80-90psi and once warm and cruising it holds around 70psi. Could there be some trash in the filter housing that occasionally gets sucked up and blocks flow at low rpm?

Sent from my paperweight
 
Almost sounds like its just breaking in. Holding 70psi once warm sounds healthy. Does it constantly fluctuate between 80-90 and 70psi or just cold and when warm is when it drops ?
 
While cold it has a constant 70+ psi. When warm it maintains 60-70 while driving. As soon as it drops to idle it will go to just below 40 psi. And occasionally it will drop to 0. It stopped doing it for awhile till Saturday. I parked facing downward on a slope and as soon as it got to idle it dropped psi. It wasn't a very steep slope so I don't believe that oil wasn't at the pickup tube.
I may swap to a heavier weight oil and see if that helps any.

Sent from my paperweight
 
Okay that makes more sense now. Did you by chance change the oil pump with the rebuild ? I seen you said the sender was new.
 
Idle having direct effect with the pressure staying up, sounds like a pump. Beings it is gear driven.
 
murphy41 said:
Okay that makes more sense now. Did you by chance change the oil pump with the rebuild ? I seen you said the sender was new.
Click to expand...

No I didn't replace it. I cleaned it and looked it over closely and it looked great. It's a positive displacement pump, so it either works all the time or doesn't lol. After talking with several other shops and asking their thoughts, they all said the same thing. No one had ever seen or heard of one intermittently failing.

Sent from my paperweight
 
Yea usually they either work or don't which is weird. But that would be my guess with having to keep rpm up to keep good oil pressure. Specially with it being a fresh rebuild.
 
dieselracer07 said:
No I didn't replace it. I cleaned it and looked it over closely and it looked great. It's a positive displacement pump, so it either works all the time or doesn't lol. After talking with several other shops and asking their thoughts, they all said the same thing. No one had ever seen or heard of one intermittently failing.

Sent from my paperweight
Click to expand...

New sending unit bad? Electronics fail brand new, as I'm sure you know. That or dash may have issues too?

Maybe T in a mechanical gauge on filter housing to see for sure.
 
Add a mechanical gauge to the oil filter housing and randomly check the pressure. There is either an issue or not that way.
 
I vote oil pressure sensor. I replaced mine twice on my 98 in less than a month. Same symptoms

Sent from my DROID RAZR using Tapatalk 2
 
homewrecker said:
I vote oil pressure sensor. I replaced mine twice on my 98 in less than a month. Same symptoms

Sent from my DROID RAZR using Tapatalk 2
Click to expand...

I have the mechanical gauge to install. I just haven't had time yet. If it happened at all sorts of random times I would point to the sending unit, but every time it does it, it's under the same circumstances.

Sent from my paperweight
 
Mine only did it once warm and at idle or off throttle intermittently. Would drop to zero, get the check engine light. Would go back to normal with any rise in rpm's.

Sent from my DROID RAZR using Tapatalk 2
 
homewrecker said:
Mine only did it once warm and at idle or off throttle intermittently. Would drop to zero, get the check engine light. Would go back to normal with any rise in rpm's.

Sent from my DROID RAZR using Tapatalk 2
Click to expand...

Well that's encouraging to know that it's most likely the sending unit. I'd hate to truly have a pressure problem. Especially after spending a damned fortune on this engine lol. I'll buy another one and pop it in.

Sent from my paperweight
 
I'm hoping it turns out to be only a sending unit for you. Hate to see something like a pump problem after a fresh build !
 
murphy41 said:
I'm hoping it turns out to be only a sending unit for you. Hate to see something like a pump problem after a fresh build !
Click to expand...

Thank you. Yeah I would come unglued if this thing toasted itself lol. I pretty much keep my eyes glued on the gauge when I drive it.




Chevycummins said:
Check the wiring too. Make sure it doesn't have a break or bad spot.
Click to expand...

I've traced the wires and all seems fine. I'll recheck everything tomorrow. I'm going to call Mumau tomorrow and get the OEM Cummins sensor.

Sent from my paperweight
 
I'm in the middle of doing a build on mine. And can only imagine how I'd feel after getting it done and watch oil pressure fluctuate.
 
murphy41 said:
I'm in the middle of doing a build on mine. And can only imagine how I'd feel after getting it done and watch oil pressure fluctuate.
Click to expand...

It's certainly not a good feeling lol. Plus, I've had the worst luck imaginable with this truck so far.

Sent from my paperweight
 
You must log in or register to reply here.
Back
Top