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.

 

[thefrey]

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.

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.

Hm, good thought to try to change the filter. Do you have a recommended filter?

 

[swathdiver]

Hm, good thought to try to change the filter. Do you have a recommended filter?

I run either the ACDelco PF48s (just had one fail) and run K&N HP2011 the last 14 oil changes before someone took my last and had to use the PF48 that was sitting on the shelf.

 

[donjetman]

@thefrey
Here's a forum & thread that shows data (not opinion or marketing speak) about oil filter "flow" & "efficiency" .
https://bobistheoilguy.com/forums/t...ntial-testing-psid.341925/page-2#post-5789075
I hope it helps

 

[SpareParts]

There is also a thread on oil filter bypass pressure that could apply to our engines on bobistheoilguy.

 

[thefrey]

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.

Do you know how much can you expect the pressure to rise with the 2 quarts test? If it doesn't rise much, I think that would point me to the pump if anything.

Just trying to think through it all. If I'm already down there just replacing the o-ring with all the work dropping the front diff, might aswell do HV pump, pressure relief, timing chain, etc.

 

[steiny93]

Do you know how much can you expect the pressure to rise with the 2 quarts test? If it doesn't rise much, I think that would point me to the pump if anything.

Just trying to think through it all. If I'm already down there just replacing the o-ring with all the work dropping the front diff, might aswell do HV pump, pressure relief, timing chain, etc.

The 2qt test with the back of the vehicle raised is supposed to test for a bad O-ring (not a bad pump). If the O-ring was the only issue, I'd expect the psi rise to get it back into normal operating (so maybe a 15-20psi raise).

Personally, I wouldn't drop the pan, I'd do everything from the front, an easy 3hrs and you'll be finished.

 

[rdezs]

.... Although that doesn't let you replace or plug the oil pressure relief valve in the oil pan.

 

[thefrey]

I would assume I would want to address or plug the pressure relief at some point.

Do you need to drop the front diff to address oil cooler lines? I haven't looked into it much but I saw somewhere you do - I have a slight oil leak from my oil cooler lines

 

[steiny93]

.... Although that doesn't let you replace or plug the oil pressure relief valve in the oil pan.

correct, but... since you have to take the timing cover off to swap the oil pump. If you start with the work (o-ring/pump) from the front first, zero rework if you later need to go into the pan for the relief valve.

 

[rdezs]

You can get away with lowering it a bit, although I prefer to go ahead and drop it. It's not that bad, basically three bolts, CV axle bolts, and one vent tube.

I got away from the OEM oil cooler lines that are problematic, on a 6.0 I have in a Hummer.

Well I went with an external oil cooler, basically to get away from the risk of the one in the radiator leaking..... You can buy 10AN fittings that screw in at the OEM location. You'll never have to deal with the rubber sections of the OEM hoses that always start to leak.

 

[thefrey]

You can get away with lowering it a bit, although I prefer to go ahead and drop it. It's not that bad, basically three bolts, CV axle bolts, and one vent tube.

I got away from the OEM oil cooler lines that are problematic, on a 6.0 I have in a Hummer.

View attachment 450893

Well I went with an external oil cooler, basically to get away from the risk of the one in the radiator leaking..... You can buy 10AN fittings that screw in at the OEM location. You'll never have to deal with the rubber sections of the OEM hoses that always start to leak.

That upgrade looks clean. What hoses/fittings did you use? Did you use a kit? Might use the derale adapter and use the steel hose to the OEM cooler.

 

[rdezs]

It's a Derale oil cooler block that replaces the OEM to the oil pan. Put together my own stainless steel braided lines with the fittings, all of it was the Evil Energy brand.

Derale

Radiator fitting

 

[rdezs]

Here's the correct link for the fittings for the radiator

EVIL ENERGY 10AN Male Flare to M20 x 1.5mm Male Metric Fitting Adapter Aluminium Alloy 2PCS https://a.co/d/bT72w66

 

[thefrey]

Here's the correct link for the fittings for the radiator

EVIL ENERGY 10AN Male Flare to M20 x 1.5mm Male Metric Fitting Adapter Aluminium Alloy 2PCS https://a.co/d/bT72w66

Sweet. Thank you for the info

 

[rdezs]

I think it would be wise to drop the pan, pull the front cover and take care of business ....

.... And think about doing a delete on the AFM system if you plan on keeping it for a long time.