Low(ish) Oil Pressure issues.

[Bimmerjo]

Hey everyone I have oil pressure concerns. My issues don't immediately reflect other issues I've found so that's why I'm creating a new thread. So here it goes.


I've owned this '07 Denali (6.2L Non DOD) since ~140k and the symptoms have always been the same. With that said, at 150k I did install factory style oil cooler plumbing that routes it to the cooler in the radiator because I'd planned to tow quite a bit. About 1k miles ago, oil pressure switch was changed. Along with timing cover gasket, valve cover gasket and valley cover gasket. Previous owner had the pickup o-ring replaced at about 130k. Currently have about 185k on the clock.


Symptoms:


Cold (~32F) start, oil is at 30-35psi at idle. Upon acceleration it will climb a little to 40-45.

As it warms up (~80F), pressure will surprisingly increase. It will make it to about 40psi at idle.

Hot (~200-230F oil temp) unloaded idle is at ~20psi

Hot loaded idle is around ~16psi.

Hot cruising (~1500rpm) speed it will stay at ~28psi to ~35psi.


It builds pressure rather quick to ~30psi after idle but the RATE at which it builds pressure falls off very quickly after 2k rpms. Even at redline, pressure never makes it to 55psi.


I've only recently learned there is a secondary relieve valve in the pan. Would these symptoms be indicative of a relief valve failure? Or do you think it's a pump issue? Or a combination of both?


To reiterate, I have had these symptoms from the beginning prior to oil cooler and the new pressure sending unit. I've used a variety of different oil filters as well. Mobile one Advanced Synthetic is always changed at around 50%-25% oil life on the clock. I use a filter cutter and inspect the filter element after each change. I always locate "some" glitter but never had chunks or a "huge" amount of glitter.

 

[OR VietVet]

At that mileage, the small amount of glitter should be ok. BUT, small amount to me may not be to you. Bearing wear could be a concern.

Where in Mo.?

 

[OR VietVet]

Might want to send an oil sample in for analysis.

 

[rdezs]

1. AC Delco or genuine GM oil pressure sending unit was installed? If not, I'd take care of that first and also verify your oil pressure with a mechanical gauge. (Look online, you can pick up a tee fitting that goes under your oil pressure sending unit with a 1/8 NPT Port off to the side that you can hook a mechanical gauge into.... When done just install a 1/8 npt plug into the port)
2. Not sure if you have the oil pressure relief in the oil pan. Can't recall exactly when they started installing those. But if so, yes that's a possibility.
3. You're not in any danger zone yet, but it's good that you're noting the change in pressure.
4. Sending an oil sample in is always a good idea... Not just for this, but just for peace of mind at set intervals. I send one in every 20,000 miles.
5. With your mileage, I would suspect either the oil pump pressure relief is gummed up, or your front camshaft bearing is showing some wear.
6. As for the oil pump, it probably needs replaced at this mileage anyway.
7. As for the camshaft bearing up front, it's the one that wears out first. While many people on a budget have simply changed out that front bearing easily enough, nobody can really say how much time that buys you. If it's a camshaft bearing scenario, the correct course of action is to tear down the motor and do all the cam bearings.... At that point you're looking at rebuilding the whole motor. This is where the oil sample becomes quite valuable. It will tell you if you have a camshaft bearing on the way out. That oil sample can save you a lot of money on an unnecessary tear down. A lot of things to consider if it comes to that. Condition of the rest of the vehicle, do you plan on keeping it for years, budget, etc.

For what it's worth, when I tore into our 2014 Escalade last year at about 145,000 miles with similar oil pressure readings.... Needed to do the AFM delete anyway... When I disassembled the oil pump relief, I found several tiny pieces of grit in there and the plunger was hanging up.