Do I have an oil pressure problem?

[rbattelle]

My oil pressure gauge (the real aftermarket one I have, NOT the fake factory gauge) acts strange. At highway speeds in 6th gear >2000 RPM the pressure will jump around between about 70 psi and 100 psi (maximum on the gauge). I mean, it's all over the place between 70 and 100. If I slow down to <2000 RPM, it will stabilize at around 65-70 psi and hold there. Idle is 20 psi, rock solid.



Funny thing is, if I'm sitting still and rev the engine to >2000 RPM, the gauge just holds steady at 65-70 psi... no jumping around at all. It's only under load on the highway that this strangeness occurs.



It's an Isspro gauge, and it's a replacement from one I had warrantied. I had them warranty the last one I had for doing the same thing, because I (and they) thought it was a sending unit problem.



Now, the "fake" factory gauge, which should peg itself to the right for pressure >75 psi, reads perfectly normal during all this. Also note that the oil bypass valve is supposed to open at 75 psi, from what I understand.



I'm interested in opinions on whether I should be concerned with this behavior or not. Anyone else with an aftermarket gauge experience anything even remotely similar? Much appreciated...

 

[CoastyAV8R]

It sounds like you may have air near or at the sending unit. I know in previous experiences, I had a fuel pressure gauge going all over the place until I bled the air out. It's a possibility. Why it isn't doing it all the time? Not sure. Maybe the higher pressure causes greater fluctuations that you can see on the gauge...

 

[rbattelle]

Originally posted by CoastyAV8R

It sounds like you may have air near or at the sending unit. I know in previous experiences, I had a fuel pressure gauge going all over the place until I bled the air out. It's a possibility. Why it isn't doing it all the time? Not sure. Maybe the higher pressure causes greater fluctuations that you can see on the gauge...

Hmmm... an interesting thought.

 

[rbattelle]

Okay, I've resolved myself that this is a problem with the Isspro sending unit. I had one go bad and behave exactly the same way on me just a few months ago. They said they had a bad batch of sending units, and sent me a new gauge, no questions asked. The "new" sending unit has exactly the same manufacture date, and other than the QC number is stamped with all the identical markings from the one I had replaced.



It seems obvious I got another bad one. This is really annoying.

 

[rbattelle]

Update

This is NOT a sending unit problem. I believe there are 2 issues:



1. The Isspro sending unit has a very fast response (this is actually a good thing).

2. The oil pressure port atop the filter assembly experiences a lot of "churning" and, perhaps, air entrainment.



I was able to fix this and stabilize my readings by connecting a 3 ft. hydraulic line to the pressure port and mounting the sending unit at the end of that. Voila - stable readings!



BTW, I needed the hydraulic hose for my upcoming install of a TP bypass filter.