Sanity Check...low oil pressure

[kevinmerlo]

Hey Guys,

I'm looking for the common low oil pressure problem on my '07 non-AFM Denali XL with the 6.2. Decent pressure when cold, after warmed up and sitting at idle it drops down just above the red line meaning single digit oil pressure. I know about the o-ring and I know about the oil pressure sensor screen thanks to you all.

I ordered the tool that replaces the oil filter so I can install a mechanical oil pressure gauge. My thinking is this: if the mechanical gauge matches the gauge on the dash it's an actual low oil pressure problem and I'll go after the o-ring. If the mechanical oil pressure is quite a bit higher than the indicated oil pressure on the gauge then the sensor is lying and I need to suspect the screen and/or sensor. Either way, it makes sense to me to validate actual pressure before going one direction or the other because both options are a fair amount of work. Does that sound like a sound action plan? If it's actual low oil pressure I'm not sure what I'd go after if the screen/sensor isn't the cause but for now that's the way I'm going.

Thanks!

 

[Geotrash]

I’m battling this right now with both a new O-ring and sensor in the middle of a cam swap. Any one of the following can result in persistent low oil pressure and it’s a matter of probabilities to determine where to start and where to go next.

Your approach to test real oil pressure before tackling either the o-ring or the sensor screen based on what you find. In order of probability on your engine I would say:

1/ sensor screen clogged
2/ pickup tube o-ring and/or debris in the pickup tube screen
3/ leaking camshaft thrust plate gasket
4/ worn camshaft bearings
5/ worn oil pump
6/ stuck or weak oil pressure relief valve in the oil pan
7/ worn main bearings

Some combination of the above.

Cheers,
Dave


Sent from my iPhone using Tapatalk

 

[Geotrash]

I’m battling this right now with both a new O-ring and sensor in the middle of a cam swap. Any one of the following can result in persistent low oil pressure and it’s a matter of probabilities to determine where to start and where to go next.

Your approach to test real oil pressure before tackling either the o-ring or the sensor screen based on what you find makes good sense. In order of probability on your engine I would say:

1/ sensor screen clogged
2/ pickup tube o-ring and/or debris in the pickup tube screen
3/ leaking camshaft thrust plate gasket
4/ worn camshaft bearings
5/ worn oil pump
6/ stuck or weak oil pressure relief valve in the oil pan
7/ worn main bearings

Some combination of the above.

Cheers,
Dave


Sent from my iPhone using Tapatalk

 

[kevinmerlo]

I’m battling this right now with both a new O-ring and sensor in the middle of a cam swap. Any one of the following can result in persistent low oil pressure and it’s a matter of probabilities to determine where to start and where to go next.

Your approach to test real oil pressure before tackling either the o-ring or the sensor screen based on what you find. In order of probability on your engine I would say:

1/ sensor screen clogged
2/ pickup tube o-ring and/or debris in the pickup tube screen
3/ leaking camshaft thrust plate gasket
4/ worn camshaft bearings
5/ worn oil pump
6/ stuck or weak oil pressure relief valve in the oil pan
7/ worn main bearings

Some combination of the above.

Cheers,
Dave


Sent from my iPhone using Tapatalk

Thanks for the reply. I should have mentioned it's got 185,000 miles on it. I just bought it so I can't speak to the history on it.
Thanks again...

 

[Just Fishing]

Hopefully it's the o-ring worst case.

I did the o-ring on my 5.3 afm engine, it was old and sorta flattened.
seemed to fall off the tube, but it stuck in the pump pretty well when i removed the pickup tube...

it broke with a good bend, but was still pliable for the most part.

doing it again, i would have yanked that front cover and at least checked the oil pump bypass before slapping it together.

My issue was not fixed, pretty much 0 change.

I'm now going all in with a cam swap and full AFM delete.
New Melling pump for good measure as well

While disassembling, i found my valley plate bolts were finger tight.
check that before going to far into this.
I'm not sure if the 6.2 non AFM has the passage ways or not, but if loose you can loose oil pressure.

 

[iamdub]

Hey Guys,

I'm looking for the common low oil pressure problem on my '07 non-AFM Denali XL with the 6.2. Decent pressure when cold, after warmed up and sitting at idle it drops down just above the red line meaning single digit oil pressure. I know about the o-ring and I know about the oil pressure sensor screen thanks to you all.

I ordered the tool that replaces the oil filter so I can install a mechanical oil pressure gauge. My thinking is this: if the mechanical gauge matches the gauge on the dash it's an actual low oil pressure problem and I'll go after the o-ring. If the mechanical oil pressure is quite a bit higher than the indicated oil pressure on the gauge then the sensor is lying and I need to suspect the screen and/or sensor. Either way, it makes sense to me to validate actual pressure before going one direction or the other because both options are a fair amount of work. Does that sound like a sound action plan? If it's actual low oil pressure I'm not sure what I'd go after if the screen/sensor isn't the cause but for now that's the way I'm going.

Thanks!

You're correct in verifying the pressure with a mechanical gauge. So many want to just start throwing parts at these without verifying the pressure that the gauge is displaying is accurate, and these are known for having wonky gauges and pressure sensors do fail. If you do have low pressure, there's a cheap and easy way to check the O-ring. I forget which years, but some of the 6.2s didn't have AFM, but they had the components in place and it just wasn't turned on in the tune. If you have the AFM VLOM, then you have another possible pressure leak point (eight, actually) that is also a relatively easy fix.

Report back with your actual oil psi findings and we'll help you from there!

 

[kevinmerlo]

You're correct in verifying the pressure with a mechanical gauge. So many want to just start throwing parts at these without verifying the pressure that the gauge is displaying is accurate, and these are known for having wonky gauges and pressure sensors do fail. If you do have low pressure, there's a cheap and easy way to check the O-ring. I forget which years, but some of the 6.2s didn't have AFM, but they had the components in place and it just wasn't turned on in the tune. If you have the AFM VLOM, then you have another possible pressure leak point (eight, actually) that is also a relatively easy fix.

Report back with your actual oil psi findings and we'll help you from there!

Thank you...I will report back. The valley plate on my truck doesn’t look like the one with all the passages in it. It’s a relatively flat piece. My build date is October 2006 so that too (I think) lends itself to not having the AFM equipment in it.

Somebody said somewhere to overfill the crankcase (I assume to be higher than the level of the o-ring) and that’s how you can verify a bad o-ring. That seems awfully high into the bottom of the engine for the oil level to be. Is that the easy o-ring check you refer to? I don’t have the tool in hand yet to check oil pressure but I will report back.
Thanks everybody.

 

[Rocket Man]

Thank you...I will report back. The valley plate on my truck doesn’t look like the one with all the passages in it. It’s a relatively flat piece. My build date is October 2006 so that too (I think) lends itself to not having the AFM equipment in it.

Somebody said somewhere to overfill the crankcase (I assume to be higher than the level of the o-ring) and that’s how you can verify a bad o-ring. That seems awfully high into the bottom of the engine for the oil level to be. Is that the easy o-ring check you refer to? I don’t have the tool in hand yet to check oil pressure but I will report back.
Thanks everybody.

People usually go 2 quarts over full I believe but then you still need to have the front downhill either by being on a steep slope or raising the rear onto jack stands. Hopefully someone else will verify the 2 quarts.

 

[Geotrash]

Thank you...I will report back. The valley plate on my truck doesn’t look like the one with all the passages in it. It’s a relatively flat piece. My build date is October 2006 so that too (I think) lends itself to not having the AFM equipment in it.

Somebody said somewhere to overfill the crankcase (I assume to be higher than the level of the o-ring) and that’s how you can verify a bad o-ring. That seems awfully high into the bottom of the engine for the oil level to be. Is that the easy o-ring check you refer to? I don’t have the tool in hand yet to check oil pressure but I will report back.
Thanks everybody.

The L92 engine is the one you have. I have it in my '07 as well. It has the towers cast into the block for the AFM system but it doesn't have the AFM lifters, and it has a flat valley pan with o-rings on the bottom of it designed to seal the AFM towers. Those o-rings can leak pressure as the engine ages and they get more hardened and brittle. I don't know why I didn't include it in my list of probable leak points for pressure loss. My only excuse is it had been a long day.

Replacing the valley pan is a viable solution, as is sealing the towers with specially designed plugs that you drive in with a dead blow hammer. If the towers are leaking, I would expect it to show up on the mechanical oil pressure gauge as a rapid fluctuation of pressure as oil builds up enough to squish through the leaking tower seal and the pressure drops momentarily.

 

[kevinmerlo]

People usually go 2 quarts over full I believe but then you still need to have the front downhill either by being on a steep slope or raising the rear onto jack stands. Hopefully someone else will verify the 2 quarts.

Thank you!

 

[kevinmerlo]

The L92 engine is the one you have. I have it in my '07 as well. It has the towers cast into the block for the AFM system but it doesn't have the AFM lifters, and it has a flat valley pan with o-rings on the bottom of it designed to seal the AFM towers. Those o-rings can leak pressure as the engine ages and they get more hardened and brittle. I don't know why I didn't include it in my list of probable leak points for pressure loss. My only excuse is it had been a long day.

Replacing the valley pan is a viable solution, as is sealing the towers with specially designed plugs that you drive in with a dead blow hammer. If the towers are leaking, I would expect it to show up on the mechanical oil pressure gauge as a rapid fluctuation of pressure as oil builds up enough to squish through the leaking tower seal and the pressure drops momentarily.

Very interesting...thank you!

 

[iamdub]

Thank you...I will report back. The valley plate on my truck doesn’t look like the one with all the passages in it. It’s a relatively flat piece. My build date is October 2006 so that too (I think) lends itself to not having the AFM equipment in it.

Somebody said somewhere to overfill the crankcase (I assume to be higher than the level of the o-ring) and that’s how you can verify a bad o-ring. That seems awfully high into the bottom of the engine for the oil level to be. Is that the easy o-ring check you refer to? I don’t have the tool in hand yet to check oil pressure but I will report back.
Thanks everybody.

Yup. As the others said- overfill it by 2 quarts and put it in a slight nosedive (sloped driveway, rear up on a curb, etc.) to ensure the O-ring is submerged. I believe the original instructions were 1-1.5 quarts, but I really think this may not be enough. I recall someone performing this test and it didn't improve their problem, so they began throwing parts and efforts elsewhere. Then, when they went to change the pump, found out that the O-ring actually was cracked and split. Also, with how these engines consume oil, some people may be low on oil from the start so that first half quart or so of "extra oil" is just getting it up to the normal level. Doing two quarts and nosediving it pretty much rules out all of these factors. It's a harmless test and you can drain the oil back out. Some even drive around with it overfilled and report no problems. I wouldn't do this, though.

Yes, the non-AFM engines will have the smooth VLOM. I don't ever recall if the non-AFM engines have the towers or AFM lifters than aren't active or what. @Geotrash kinda reminded us of the details. Still, as he said, those O-rings can age and collapse and allow pressurized oil to leak out. It's the same as internal bleeding causing one's blood pressure to drop.

 

[kevinmerlo]

Yup. As the others said- overfill it by 2 quarts and put it in a slight nosedive (sloped driveway, rear up on a curb, etc.) to ensure the O-ring is submerged. I believe the original instructions were 1-1.5 quarts, but I really think this may not be enough. I recall someone performing this test and it didn't improve their problem, so they began throwing parts and efforts elsewhere. Then, when they went to change the pump, found out that the O-ring actually was cracked and split. Also, with how these engines consume oil, some people may be low on oil from the start so that first half quart or so of "extra oil" is just getting it up to the normal level. Doing two quarts and nosediving it pretty much rules out all of these factors. It's a harmless test and you can drain the oil back out. Some even drive around with it overfilled and report no problems. I wouldn't do this, though.

Yes, the non-AFM engines will have the smooth VLOM. I don't ever recall if the non-AFM engines have the towers or AFM lifters than aren't active or what. @Geotrash kinda reminded us of the details. Still, as he said, those O-rings can age and collapse and allow pressurized oil to leak out. It's the same as internal bleeding causing one's blood pressure to drop.

Thank you! All my parts and accessories should start rolling in late this week and over the weekend so I'll dive right in as soon as I can. Thanks again.

 

[Rocket Man]

Thank you! All my parts and accessories should start rolling in late this week and over the weekend so I'll dive right in as soon as I can. Thanks again.

What parts and accessories did you order? What’s your plan at this point?

 

[1BADI5]

^^ Yeah that, or is it just the "Parts Cannon" being engaged?

 

[avalonandl]

Ahhh one thing....If you do the overfill to check the oil pressure, remember to drain the excess out before driving....

 

[swathdiver]

Ahhh one thing....If you do the overfill to check the oil pressure, remember to drain the excess out before driving....

A guy on here drove his for 2 years until he had the dough to fix it, said it didn't hurt a thing.

 

[avalonandl]

A guy on here drove his for 2 years until he had the dough to fix it, said it didn't hurt a thing.

Aerating your oil is BAD...

 

[Erock7625]

What wasnt answered here is what is considered normal for a high mileage engine. I had the P0521 code, and had about 20 psi at 2,000 rpm and about 10 psi at hot idle, would get up to about 25 psi at higher rpm. Running Mobil 1 5w30 in the 5.3 engine on a 2011 Yukon XL SLT with around 147,000 miles. Had the sensor and screen replaced and that didnt change my oil pressure readings. Now my P0521 is back and Ive been reading through the other possible causes such as the O ring. But what do others get for oil pressure on a 150k+ mile engine at hot idle and 2,000 rpm? Just trying to get a benchmark for what is considered normal.

 

[donjetman]

stock non-AFM 2007 6.2L L92, 164k miles, 5w30 oil, 20 hot idle, 45 cold idle, 35 hot going down the hwy. Changed the pickup oring at 130k miles. Engine with AFM should have a little more oil pressure.

 

[FrankU]

stock non-AFM 2007 6.2L L92, 164k miles, 5w30 oil, 20 hot idle, 45 cold idle, 35 hot going down the hwy.

Exactly what my 6.2 does on the dash.