Low oil pressure diag

[nvanzee]

I've done a lot of reading trying to narrow down my issues but not having much luck.
08 Yukon 6.2. 260k original miles. Runs great but have been having some oil pressure issues. On cold start the pressure will go up to 8-10 for a few seconds then slowly go up to about 35. Once it's warmed up I have 12psi at idle. Pressure is slow to respond with acceleration.
Thinking maybe the pickup oring which is easy to do. But thinking it could be the pump also. Or just worn bearings....
Trying to do fix it the quickest and most cost effective way. Just don't want to throw an oring in it just to have it not fix anything and have to tear it back down and farther for the oil pump. Then maybe neither of those do it and it just needs a complete rebuild.
I can do all the work myself. Just have limited time and funds.
Anyone have a more direct way of figuring out the main issue? I am testing pressure with a mechanic gauge at the oil filter housing. I know overall the pressures aren't the worst. I'm just worried about the low at startup and that it's slow to respond and build pressure.

Also, I tried switch to a 10w40 oil. Still behaves the same way but pressure is is maybe 5psi higher cold and 2-3 psi higher once warm

 

[j91z28d1]

there's a sticky thread just above your post about oil pressure with good info.

the test for the o ring is add 2 qt of oil and face it down a hill. that will cover the o ring with oil so it can't suck air. if the oil pressure goes up, it was sucking air pasted the o ring.


probably end up putting a high volume pump in it to cover for whatever is causing the low oil and drives it till you decide it needs rebuilt.

 

[rdezs]

At that mileage.... I would just do the oil pump with a high volume Melling 365.

Comes with the o-ring you will need. If it's a bearing issue with a bit too much clearance, it could buy you a lot of time. Also, the oil pressure relief valve in the OEM pump does tend to get gummed up with crap and create issues with pressure.

 

[Joseph Garcia]

Drop the oil pan and replace the O-ring, and install an aftermarket 2 bolt clamp fitting to better secure the pickup tube to the block.

If your oil pan has an oil pressure relief valve in it, either replace it AND get the GM-approved deflector shield with it, or plug it with an aftermarket threaded plug, as you don't have AFM, and thus do not need the oil pressure relief valve.

The 2 aftermarket items mentioned above can be readily purchased from Summitracing.com or Texasspeed.com, and other performance web sites, as well.

 

[rdezs]

His 2008 Yukon shouldn't have AFM or the pressure relief valve in the oil pan.

Should be the L92 if I remember correctly.... Well worth rebuilding.

And that also eliminates several areas where oil pressure problems can originate. (The screen under the sending unit, the VLOM plate, oil pressure relief valve in the oil pan... He won't have any of that)

 

[SpareParts]

It will for sure have the valve in the oil pan. 07-09 L92 did not get a screen under the oil pressure sensor that i have ever seen.
You can band-aid it with a new O ring and a Melling HV oil pump. Could last hours or years. My bet would be years. Been through the exact same problem on 3 L92s.

 

[donjetman]

It will for sure have the valve in the oil pan. 07-09 L92 did not get a screen under the oil pressure sensor that i have ever seen.
You can

My 07 Denali w/6.2L L92 didn't come with AFM/DOD hardware but did come with the pressure relief valve. I installed the deflector shield.

 

[donjetman]

I've done a lot of reading trying to narrow down my issues but not having much luck.
08 Yukon 6.2. 260k original miles. Runs great but have been having some oil pressure issues. On cold start the pressure will go up to 8-10 for a few seconds then slowly go up to about 35. Once it's warmed up I have 12psi at idle. Pressure is slow to respond with acceleration.
Thinking maybe the pickup oring which is easy to do. But thinking it could be the pump also. Or just worn bearings....
Trying to do fix it the quickest and most cost effective way. Just don't want to throw an oring in it just to have it not fix anything and have to tear it back down and farther for the oil pump. Then maybe neither of those do it and it just needs a complete rebuild.
I can do all the work myself. Just have limited time and funds.
Anyone have a more direct way of figuring out the main issue? I am testing pressure with a mechanic gauge at the oil filter housing. I know overall the pressures aren't the worst. I'm just worried about the low at startup and that it's slow to respond and build pressure.

Also, I tried switch to a 10w40 oil. Still behaves the same way but pressure is is maybe 5psi higher cold and 2-3 psi higher once warm

Just shim the stock oil pump relief valve for more psi

 

[SpareParts]

The problem i have figured out is more pressure really does nothing. It's already leaking past the bearings so fast the relief valves are not even close to opening.
You need more volume to fill the voids faster than it can drain out and this gives you more pressure.
The first L92 i put in a HP pump in and it did not do much at all.
Had to take it back apart and i tried a HV pump and i swapped the spring to i think orange that gave a significant jump in pressure. Volume was the key.

With my current installed engine before i put it in i installed new cam bearings and used the stock pump. Cold oil pressure is 60ish psi and hot idle oil pressure 30ish psi.
I'm assuming the oil pan valve blows off around 60psi? im really not sure. The only ones i have seen higher have no valve or were plugged.
I really believe every L92 with low oil pressure will have bad cam bearings if it's under 20psi hot idle and a bad O ring that needs to be changed also at 150K or more.

 

[donjetman]

Every first start of the day (winter or summer) my 200+k mile L92 oil pressure at idle goes to about 55 psi. I can raise the rpm up and pressure doesn't increase so I know the oil pump relief/bypass is opening at 55 psi. If I shimmed (or changed) its spring I could get more pressure hot and cold. But why? volume is more important.

 

[Joseph Garcia]

Every first start of the day (winter or summer) my 200+k mile L92 oil pressure at idle goes to about 55 psi. I can raise the rpm up and pressure doesn't increase so I know the oil pump relief/bypass is opening at 55 psi. If I shimmed (or changed) its spring I could get more pressure hot and cold. But why? volume is more important.

The oil pressure relief valve is designed to open at ~60 psi. The problem is that over time small deposits build up on the valve surfaces, causing it to open/leak at oil pressures less than 60 psi, and it will continue to deteriorate in this direction over time. In my case, it deteriorated to the point that I could not get more than 30 psi at any rpm, and this was the second valve since I purchased the truck used 5 years ago (because I had to replace the oil pan once, due to a crack). I'm glad that this valve has been deleted now on my truck.

 

[nvanzee]

Thanks for the help. Not sure how I missed the sticky at the top.
Gonna try an extra couple quarts and see what that does. Probably end up putting a HV pump in it though

 

[Geotrash]

Thanks for the help. Not sure how I missed the sticky at the top.
Gonna try an extra couple quarts and see what that does. Probably end up putting a HV pump in it though

Hundred bucks says it’s the o-ring. But you might as well put a HV pump in it while you’re in there.

 

[nvanzee]

Figured I'd give an update. Took the time to just replace everything. O-ring, hv oil pump, pick up tube, pressure relief in the pan, and the barbell. Now on cold start I get about 55psi. But once it's hot I'm right back down to about 9-10 at idle unfortunately. Guessing it's just getting to worn out with the miles and its getting through the bearings.

 

[swathdiver]

Figured I'd give an update. Took the time to just replace everything. O-ring, hv oil pump, pick up tube, pressure relief in the pan, and the barbell. Now on cold start I get about 55psi. But once it's hot I'm right back down to about 9-10 at idle unfortunately. Guessing it's just getting to worn out with the miles and its getting through the bearings.

Your truck came with the M365 oil pump. What did you replace it with? An aluminum engine gets a pump that runs at a lower pressure and pumps 1/3 more oil per revolution to compensate for the expansion of an aluminum engine.

 

[SpareParts]

M365HV is the pump to get for more volume.

 

[rdezs]

Unfortunately, sounds like the cam bearings....

 

[builds4christ]

I just picked one up with the same issues. Motor has around 192k on it.

After it warms up, it settles around 15 psi.

Got the HV melling pump and oring kit. Hopefully that helps. I there a practical way to check if it's cam bearings apart from taking apart? I can't imagine so.

15 psi scares this crap out of me, especially since my L31 in my sierra runs at 40psi after it's hot.

 

[SpareParts]

Just put the pump and o ring in it. It will be fine. Your cam bearings are worn im sure.
I would bet your oil pressure jumps up to are 25PSI hot idle.

 

[07burban88]

MELLING M29500 High Performance; No Warranty Info
Uses The Unused Bolt Hole In The Oil Pump; Does Not Fit Pickup Tube w/ Welded Flange GM Part Number 12608593; Does Not Fit Pickup Tubes w/ Two Bolt Hole Flanges

i used this when i did the 4.8 swap into my 07 Burban along with the Meling high volume pump it