Low(ish) Oil Pressure issues.

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.

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.?

Might want to send an oil sample in for analysis.

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.

being a non afm engine, I would guess there's no reason for the 2nd relief valve. if you ever have the pan off again, if it's even there. Just plug it.


I don't think you have anything to worry about. but I am curious about the glitter. as in how much, like a few specs? I have been cutting filters of random engines open over the last year or so and if you can get all the oil off the media. I lay it clean side down on pig mat and it sucks it dry over night. it's a bit surprising at first how many specs of metal you see. mostly sticks to a magnet too, which rules put some things that would commonly wear like piston side skirts. but you don't even see the stuff when it's still covered in oil and never seems to be an issues. the engines show no signs of failing. all mostly really high hour considered industrial stuff that runs 6 to 12h a day.

the gm low oil spec is crazy low and if you don't have afm. I wouldn't worry about it at all till you see under 10psi hot idle and then I'd probably still put some 10w40 in it and drive on haha.

Could also simply be just the stepper motor in the cluster, I wouldn't think too much about it without checking it with a mechanical gauge. But where you're at now on pressures.... Really not a problem yet, and could literally go on for a couple years like that with no issue. I would concur with using 10w40 synthetic with the miles you have. But I'd probably wait till spring.

Bimmerjo said:

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.

Click to expand...

I have the same engine as you. Mine has 198k miles. We bought it road hard and hung up wet 6 yrs ago w/130k miles. It doesn't have an oil cooler.

All my hot pressures are the same as yours, which is normal.

First start of the day, anytime of the yr here in TX, it goes straight to 50-55psi at idle. This is probably the oil pump bypass/relief pressure. Oil filters also have a bypass in them.

In/on the oil pan is a afm pressure valve. I put a deflector ($8) on mine 6+ yrs ago per the GM TSB 10-06-01-008M:
https://f01.justanswer.com/ebrock63...il+Consumption,+MIL+ON,+Engine+Runs+Rough.pdf
and
https://www.tahoeyukonforum.com/thr...-tsb-10-60-10-008m.108493/page-2#post-1292730

I’ll put in my input, may answer some questions and someone may answer my questions.

I’ve changed out the oil sensor twice due to a leak and replaced o ring turned of AFM and replaced oil pan gaskets ect, and my oil pressure was still 16-20 hot idle. I finally caved in and put on a mechanical gauge with 15w-40 while the manifold was off. Mind you it’s a PPV with a lot of idle hours so bearing clearances are probably worn out by a lot. With oil cooler.

Oil pressure on the mechanical gauge right of the oil sensor hole read 24-25 psi hot. With 1-3 psi variances not flickering fast but slow up and down flickering between 1-2 sec or so.


Put it all back together with new sensor on.
The cluster gauge reads 16-20psi still, so i just ride on.

Cluster stepper motor if replacement sending unit reads the same. Drive on.

I wanted to chime in just really quick and say thank you for the replies. When I get a chance I'll sit down and reply individually. Thank you everyone for your input so far.