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!