Just on the one, sending unit on mine was bad, don't think that's your problem. Other forums point to the pump pressure relief valve, cam bearings, some even went with a newer sender and pigtail as in the last link above to the Pontiac G8 site.

 

Fly, my 08 the oil reading is at 40 but sometimes fluctuates bet 20/25-40. I see that on all the 08's I've been in. Is it supposed to be steady at 40?

 

Yeah I don't think mines a bad oil pressure sensor it stays at 40 psi which is correct then loses pressure once oil is less thick. I wonder what psi is when the oil pressure relief valve is stuck open?

 

Not much experience with it but I'm thinking it's variable by design. It's a gerotor type so suspect that's got something to do with it. Lots of peeps on the forum with better info on this, I'm sure.

This article has some good info on front-mounted GM pumps: Front-Mounted Oil Pumps: Good or Troublesome? - Engine Builder Magazine

 

I might put a new GM motor in next week even though this runs perfect no noise

 

Thanks for sharing, great info

Neal