Possible low engine oil pressure

[thefrey]

Newish to me 2013 Yukon XL Denali with the 6.2. 199k miles. Got it cheap because was neglected and needed lots of love

Oil pressure sending unit was stuck and tripped a CEL and was replaced around 500 miles ago along with fresh full synthetic oil

I’ve been chasing a slight tick in the engine (last owner said they did lifters 10k miles ago, didn’t delete AFM) but it doesn’t seem to be a consistent tick and is very intermittent, so it’s pointing me to oil pressure. The tick doesn’t quite sound like a stuck lifter, an exhaust leak, or a knock.

After the oil pressure sending unit, cruising oil pressure was 40 for 2 weeks and now is dropped to around 24 at 1800rpm and is about 15 at idle hot. AFM activates when the engine is cold but doesn’t when it’s hot. I believe AFM activates from oil pressure.

Assuming there is no stepper motor issues in the gauge cluster, what things could be causing the slightly low oil pressure/tick? Are they generally related (assuming lifters are ok)? Would a new o ring for the oil pickup tube possibly fix the issue? Any help is appreciated. My theory is either o-ring, plunger stuck in oil pump, or pressure relief in oil pan. Just don’t wanna throw the parts cannon at it

 

[rdezs]

You should have that little screen under the oil pressure sending unit, but if you're hearing ticking noises, along with the gauge showing somewhat low oil pressure..... The three items you referenced are all in play. Could be just one, or an accumulated combination of the three. Generally speaking, if it were cam bearings I would expect the oil pressure to start dropping shortly after starting the engine cold, increasing corresponding to the temperature increase. And then remaining steady.

I think for starters I would remove the oil pressure sending unit and the screen underneath it, install a mechanical oil pressure gauge and verify what the actual pressure is. And don't forget, you also have a bunch of o-rings under the VLOM plate in the engine valley.

Then you have the question as to what lifters were used by the previous owner, and were the push rod lengths verified.

And that 200,000 miles with AFM not deleted or even turned off.... You can throw in there the questionable condition of the solenoids.

Checking oil pressure with a mechanical gauge, and checking the lifter preload are probably a good place to start.....

 

[swathdiver]

There are a number of requirements for AFM to engage or not and the most critical is oil pressure. Oil is used to collapse the lifters.

Check your oil level and then change your oil pressure.

I just went through the same thing. We changed the oil about 3K miles ago and last week the oil pressure dropped to 19-20 psi at idle in gear and to about 30 psi while cruising instead of 38. We changed the oil filter tonight and added about a quart of oil and she's back to normal. 25 psi at idle in gear and near 40 when underway.

Incidentally, we also had a P0521 code and replaced the oil pressure sensor too. Since AFM is turned off, the little filter underneath is long gone.

 

[steiny93]

I just went through similar scenario https://www.tahoeyukonforum.com/threads/2007-oil-pressure-thread-with-success.153047/

You've hit on 3 options; other could be clearances in the engine allowing for a lower psi.

For me, I went the pump / O-ring route as the costs were low (<$200, pump/gaskets/bolt) and by doing a new high-volume pump I would know that the engine would be getting plenty of oil. IE, even if the root cause is bearing clearance, high volume pump will raise the psi.

I would recommend a manual gauge to verify psi, if it matches the dash, I'd vote for pump which means O-ring as you are already there. You can also over fill by 2 quarts and raise the rear of the vehicle, if pressure rises it points to O-ring.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.