Low/No Oil Pressure After new Oil Pump Install

[nadthomas]

I'm really hoping that someone schools me on something that I have overlooked. Over the summer I pulled the motor out of my Denali to give it a little refresh since I'm approaching 200k miles. I replaced a bunch of seals like valve covers, timing cover, rear covers, rear main, front seal, intake gaskets. I also fixed the broken exhaust bolts, and put on new exhaust manifolds and gaskets. While I had the engine out and partially apart, I decided to replace the oil pump and the pickup tube. Prior to engine removal, from what I recall, and have read, I believe oil pressure was generally fine. 45PSI at start up and while driving, pressure would drop at idle after it was warmed up to about 30ish psi, but then would come right back up while I was driving.

The motor was out of the Denali for about 4-5 months while I did this work, and I did not touch the heads, cams, crank, timing or any of the bearings while it was out. Some how my TCM went bad during all of this, so the first startup was at my friends shop after the diagnosed the electrical issue that was causing the no start. They immediately noticed low oil pressure at the first start up. While cold at idle pressure never got beyond 20-25psi, and dropped below 10psi after a couple of minutes. They hooked up a mechanical gauge, as well as a new oil pressure sensor and got the same results. So, the dash gauge appears to be accurate

So, I had it towed back home, assuming that the new oil pump was bad, or that maybe I damaged the pickup tube o-ring. So, I pulled things appear again, so I could easily pull the timing cover and oil pump. Pulled the pump, and found no damage to the pickup tube o-ring. So I figured the new pump was bad. So, I double downed and upgraded to from the Melling M365 oil pump, to the Melling 10355 which is the High Volume/High Pressure version of the pump. I swapped out the high pressure spring as to the slightly lower pressure one, as I read the higher pressure spring will produce 65-70psi, and the lower pressure spring should be about 8-10psi lower. Still well above stock. I also replaced the pickup tube o-ring again, even though it was new. So, I just got things back together enough to test the new-new pump, and I am still only getting about 20-25psi on cold start up. I don't have the water pump hooked up, so I killed it after less then a minute. It also looked like oil pressure was already starting to drop a little. I followed Melling install instructions shimming out the pump gears during install, and this time I pulled the oil galley plug and added about a 1/2 quart of oil through the plug to prime the oil pump.

What am I doing wrong, or what have I over looked. I don't understand how I could go instantly from a vehicle with decent oil pressure to now poor oil pressure given the work I have done.

 

[01FormulaTA]

What year Denali? When you replaced the rear cover did you make sure the oil galley barbell was still in place?

 

[nadthomas]

What year Denali? When you replaced the rear cover did you make sure the oil galley barbell was still in place?

Its a 2007. Upgraded to a metal Sak city barbell while I had the cover off.

 

[swathdiver]

You didn't pull the camshaft did you? Bad cam bearings can cause poor oil pressure.

I suspect that o-ring. Either pinched or it's the wrong one. The M365 is a high volume, low pressure pump used in the aluminum engines. Cold it's just over 40 psi and idles under 30. The bypass spring is 33 psi. It pumps 1/3 more oil per revolution compared to the iron block pumps.

 

[nadthomas]

You didn't pull the camshaft did you? Bad cam bearings can cause poor oil pressure.

I suspect that o-ring. Either pinched or it's the wrong one. The M365 is a high volume, low pressure pump used in the aluminum engines. Cold it's just over 40 psi and idles under 30. The bypass spring is 33 psi. It pumps 1/3 more oil per revolution compared to the iron block pumps.

Didn't touch the cam, except for replacing the VVT oil control valve bolt. I originally bought the pick up tube and oil pump as a set from Melling. The o-rings came pre-installed, but I even measued the pick up tubes end and verified with the instructions that the correct o-ring was used. O-ring was lubed before both pump installs. After the original install I even pulled the pickup tube off twice after pushing it onto the pump to verify the o-ring still looked good. I'm kind of super **** about things. M365 is what Melling recommends as the factory replacement, and what I installed originally. The 10355 is higher volume and pressure, and what I installed yesterday with the exact same results.

I have read that the cam bearings can cause low pressure, but the vehicle has been driven 0 miles since I last had good oil pressure. So, I'm trying to exhaust all other ideas before I pull the motor for a complete rebuild.

 

[swathdiver]

Didn't touch the cam, except for replacing the VVT oil control valve bolt. I originally bought the pick up tube and oil pump as a set from Melling. The o-rings came pre-installed, but I even measued the pick up tubes end and verified with the instructions that the correct o-ring was used. O-ring was lubed before both pump installs. After the original install I even pulled the pickup tube off twice after pushing it onto the pump to verify the o-ring still looked good. I'm kind of super **** about things. M365 is what Melling recommends as the factory replacement, and what I installed originally. The 10355 is higher volume and pressure, and what I installed yesterday with the exact same results.

I have read that the cam bearings can cause low pressure, but the vehicle has been driven 0 miles since I last had good oil pressure. So, I'm trying to exhaust all other ideas before I pull the motor for a complete rebuild.

Ok, I figured about the cam. The M355 is the same volume with a 43 pound relief spring. GM quit using that pump in 2007 and went with the M365 with the other spring for the aluminum engines. The gerotors should be the same, or the M365 being substantially larger.

As for the pickup tube o-ring, there are three colors, orange/red, black and green. Green if memory serves is for tubes with a notch to capture it. Well, what motor and year are we dealing with here? L92, L9H or L94?

 

[nadthomas]

2007 L92 with no AFM.

Notched tubes use a black or blue o-ring. Staight or tapered tubes use a green or red o-ring. Again this was a new pick up tube with the o-ring pre-installed. My tube is the tapered version.

I'm 100% confident its not an o-ring issue. Before replacing the new oil pump I even overfilled the oil and jacked up the rear of the vehicle to ensure the pickup/oil pump connection would be surrounded by oil. That had no improvement on oil pressure.

 

[swathdiver]

Well Dan, I'm at a loss from my chair here, sorry. There are lots of guys here that I'm sure you know of who have been inside these motors and been around them a lot longer than I. Merry Christmas btw!

 

[swathdiver]

@Bigbertha78 @Sparky75013 @Searay45db @clandr1 @01ssreda4 @gpracer1

 

[gooffeyguy]

I'm not real familiar with the LS series engines, but does the pick-up tube rest near the bottom of the pan, and is there a chance that it's too close to the bottom causing the oil to be restricted when being sucked in?

I know on some engines the pick-up tube needs to be adjusted to be about 3/8"-1/2" above the bottom of the pan.

2001 Yukon SLT
2012 Yukon XL Denali
2011 Yukon Denali RIP 5/20/18

Sent from my SM-G930V using Tapatalk

 

[nadthomas]

I'm not real familiar with the LS series engines, but does the pick-up tube rest near the bottom of the pan, and is there a chance that it's too close to the bottom causing the oil to be restricted when being sucked in?

I know on some engines the pick-up tube needs to be adjusted to be about 3/8"-1/2" above the bottom of the pan.

2001 Yukon SLT
2012 Yukon XL Denali
2011 Yukon Denali RIP 5/20/18

Sent from my SM-G930V using Tapatalk

I have heard of that as well, but I don't think that is a thing with these and most modern motors. Someone correct me if i'm wrong. Although, i may try to pull the oil pan, so I'll inspect it if I do. I have heard that its possible to drop the AWD system a couple of inches to pull the pan.

 

[clandr1]

While I had the engine out and partially apart, I decided to replace the oil pump and the pickup tube.

I'm no expert on these motors, but am a huge fan of Occam's Razor (the simplest explanation is often the correct one). I'm wondering if your replacement oil pickup tube was out of spec when you installed it. I suppose if it's too high in the pan, or too low, that might cause some issues. Also, you might want to do a flow test to make sure there isn't something inside the tube that is impeding flow.

Do you still have the original pickup tube? If so, might be worth swapping it in and giving it a go to see if you get similar results.

Sorry I can't be more help - you've already done way more to your motor than I have with mine.

 

[01FormulaTA]

What about the O Rings on your valley cover? Why did you even replace the pick up tube? Why not just replace the o ring on the original tube?

Also I know the 07 L92 doesn’t have AFM however the early L92s DID have AFM components...LS engines with AFM used a higher volume pump than non AFM LS engines...the AFM pumps use a thicker gerotor with a larger OD than the 12586665 standard volume pump. The AFM pump is identical to the 12571885 high volume oil pump but uses a different spring...try part 12612289

 

[nadthomas]

What about the O Rings on your valley cover? Why did you even replace the pick up tube? Why not just replace the o ring on the original tube?

Also I know the 07 L92 doesn’t have AFM however the early L92s DID have AFM components...LS engines with AFM used a higher volume pump than non AFM LS engines...the AFM pumps use a thicker gerotor with a larger OD than the 12586665 standard volume pump. The AFM pump is identical to the 12571885 high volume oil pump but is uses a different by-pass spring...try part 12612289

I replaced the pick up tube because it was cheap and easy to replace with the engine out. I also did it to help ensure I had a 100% clean pick up screen, and to make sure I had the right o-ring.

Hmmmm I don't recall o-rings on the valley cover, and I didn't snap any pics of it when I had it off. Although I know my valley cover is different( ie flat) since I dont have afm. I think you may be confused, I know they later added afm to the L92 without other modifications, but I dont think my engine has any of the afm components in it. If there are o-rings on the valley cover that I missed, i could see that being a problem since the main gasket is new, the old o-rings would probably not make a good seal now. Sounds like a good thing to check since I would need to pull the intake and valley cover to install my lift plate if I end up pulling the motor again anyways.

 

[kbuskill]

How about oil filter?

Also what about the oil pressure bypass in the oil pan?

 

[nadthomas]

How about oil filter?

Also what about the oil pressure bypass in the oil pan?

Oil filter was an Acdelco, but was replaced with a Mobile1 filter between new and new-new oil pump.

The Oil pan pressure release valve was replaced when I had the engine out in the summer. So I guess another suspect for a faulty part.

 

[01FormulaTA]

I replaced the pick up tube because it was cheap and easy to replace with the engine out. I also did it to help ensure I had a 100% clean pick up screen, and to make sure I had the right o-ring.

Hmmmm I don't recall o-rings on the valley cover, and I didn't snap any pics of it when I had it off. Although I know my valley cover is different( ie flat) since I dont have afm. I think you may be confused, I know they later added afm to the L92 without other modifications, but I dont think my engine has any of the afm components in it. If there are o-rings on the valley cover that I missed, i could see that being a problem since the main gasket is new, the old o-rings would probably not make a good seal now. Sounds like a good thing to check since I would need to pull the intake and valley cover to install my lift plate if I end up pulling the motor again anyways.

Not confused at all....it’s a fact some early 07 L92s had AFM components even though they didn’t have AFM active...the 6.2s that had AFM active are the L99(Camaro) and L94(2010+ Escalade and Denali SUV)...I bet if you went back to your original pump and pickup tube you would be back to normal oil pressure...and the Valley Cover has 8 O-Rings that block off the AFM oil ports(present on all Gen 4 LS), if they aren’t sealing this could also be part of your problem

 

[01FormulaTA]

 

[01FormulaTA]

Also the fact you mention you replaced the oil pressure relief valve is another indicator your engine may have AFM components...that valve is used to bypass excess oil pumped by the high-volume oil pump when AFM is not active....if you install a standard volume pump without deleting the oil pressure relief valve it could cause low oil pressure

 

[01FormulaTA]

When comparing your valley cover to the pic below does it resemble the one on the left(AFM Style) or right(no AFM)??