VLOM, High oil pressure

RustyGunz · October 11, 2022

Oh boy, My VLOM failed recently and took out my lifters, cylinder 7. I replaced it with the latest version VLOM. I am concerned that what took it out was high oil pressure. When above 3500RPM and the high pressure oil is activated my pressure appears to climb passed 550KPA. My mechanic said he saw over 100PSI on his snap-on diagnostic tool? Is it possible that the pressure relief valve is sticking? this is only intermittent, sometimes the pressure stops at the 7/8 mark, sometimes the needle is buried.

Has anyone else seen this?

KevinRum · October 11, 2022

RustyGunz, I went through the exact same issue 4 times over and basically without my truck for 3 months. I had to demand the mechanic change the VLOM and the pressure relief valve before the high pressure and failed lifters went away. Mechanic said with every failure "higher pressure is better than lower". In the end he was sucking on that higher pressure as he had to cover the cost of each failure after the first. If I were to go through it all again, I would change the VLOM and get a plug-in AFM Bypass module and see if your pressures subside. If not, you will be into removal of the oil pan and possibly oil pump. Good luck and let us know how it goes. Note: The dealer, who I was conversing with through my difficulties, was certain the high pressures were the result of a faulty VLOM.

SeekAndDestroy · October 11, 2022

There is a new revision of the Oil Pump for the LT 5.3 and 6.2. I installed the new version when I did a cam. The shop that tuned it said they have seen Camaros and trucks lose the oil pump and destroy the engine

RustyGunz · October 11, 2022

Kevin, Thanks for the feedback. By plug in AFM bypass you mean bypassing the 4cyl mode right? curious how that would affect oil pressure? I needed my truck back for work so I have been staying away from high RPM until I get this dealt with. It really seems intermittent at the higher pressure. I have added oil treatment to see if maybe the PRV is gummed up.

Grumpy Bear · October 11, 2022

5 hours ago, RustyGunz said:

Oh boy, My VLOM failed recently and took out my lifters, cylinder 7. I replaced it with the latest version VLOM. I am concerned that what took it out was high oil pressure. When above 3500RPM and the high pressure oil is activated my pressure appears to climb passed 550KPA. My mechanic said he saw over 100PSI on his snap-on diagnostic tool? Is it possible that the pressure relief valve is sticking? this is only intermittent, sometimes the pressure stops at the 7/8 mark, sometimes the needle is buried.

Has anyone else seen this?

Your pump and VLOM are working as designed.

From the shop manual:

Hot oil pressure minimums.

22 psi @ 1,000 rpm

30 psi @ 2,000 rpm

33 psi @ 3,000 rpm

Takes 22 psig MINIMUM to properly work the lifters. Lifters don't fail from to much pressure.

They will fail from to little pressure, aeration/foaming or anything that causes these conditions. Plugged screens, low oil levels, over heated oil. Wrong oil. Leaking VLOM seals. Plugged galleys. And yes, mechanical failure of the lifter itself as well.

RustyGunz · October 12, 2022

If oil pressure was too high is it possible that it caused the solenoid in the VLOM to leak or pass oil pressure to the lifter when it wasn't supposed to which in turn causes the pins in the lifter to collapse when under load? Is the updated VLOM supposed to be more reliable? I can't seem to find any info on the oil pump PRV so maybe I am going down a rabbit hole I don't need to? sure don't want to have to go down this road again, especially trying to find a new VLOM lol. Might try e-mailing GM themselves.

Grumpy Bear · October 12, 2022

49 minutes ago, RustyGunz said:

If oil pressure was too high is it possible that it caused the solenoid in the VLOM to leak or pass oil pressure to the lifter when it wasn't supposed to which in turn causes the pins in the lifter to collapse when under load? Is the updated VLOM supposed to be more reliable? I can't seem to find any info on the oil pump PRV so maybe I am going down a rabbit hole I don't need to? sure don't want to have to go down this road again, especially trying to find a new VLOM lol. Might try e-mailing GM themselves.

No...take a solenoid apart on your old unit. Oil pressure works to close the valve, not unseat it. Yes a seat could leak but pressure would have nothing to do with it. Don't take my word for it. Take it apart of look.

https://static.nhtsa.gov/odi/tsbs/2013/SB-10071670-5448.pdf

Go to page 7. Does not have a traditional PRV. Oil pressure is controlled by the multistage pump, wear and viscosity. Temperature dependent viscosity.

RustyGunz · October 12, 2022

15 minutes ago, Grumpy Bear said:

No...take a solenoid apart on your old unit. Oil pressure works to close the valve, not unseat it. Yes a seat could leak but pressure would have nothing to do with it. Don't take my word for it. Take it apart of look.

https://static.nhtsa.gov/odi/tsbs/2013/SB-10071670-5448.pdf

Go to page 7. Does not have a traditional PRV. Oil pressure is controlled by the multistage pump, wear and viscosity. Temperature dependent viscosity.

Ahhhhh, Ok so there is no PRV to release any excess pressure when in the high stage from the looks of it (maybe that's why I can't find any info on it haha). I'll have to get my old VLOM back and check to see what's wrong with the solenoid for that cylinder. maybe the solenoid is flakey or leaks. Would sure be nice to have some confidence that it was just the VLOM that ****ed up. There is a GM bulletin somewhere that says change the VLOM with the lifters.

Since you seem knowledgeable on the subject, is it common that the oil pressure sensor is flakey? everyone I know with this truck the oil gauge (which doesn't seem very accurate or fast acting) doesn't go full scale when in high rev's. Is it common for the VLOM to be the issue?

Grumpy Bear · October 13, 2022

10 hours ago, RustyGunz said:

Since you seem knowledgeable on the subject, is it common that the oil pressure sensor is flakey? everyone I know with this truck the oil gauge (which doesn't seem very accurate or fast acting) doesn't go full scale when in high rev's. Is it common for the VLOM to be the issue?

What is common is the screen under the OPS being partially plugged. Yes you are to replace the VLOM when you do a lifter service. No the gauge is not accurate nor responsive as you suggest. Not bad at mid scale but poor at either end. Span error.

There are screens in the VLOM at each solenoid. Third line of defense. Second is the screen under the OPS. First is OCI and good oil.

RustyGunz · October 14, 2022

23 hours ago, Grumpy Bear said:

What is common is the screen under the OPS being partially plugged. Yes you are to replace the VLOM when you do a lifter service. No the gauge is not accurate nor responsive as you suggest. Not bad at mid scale but poor at either end. Span error.

There are screens in the VLOM at each solenoid. Third line of defense. Second is the screen under the OPS. First is OCI and good oil.

Ok thanks for the help, I think I’ve done all I can to avoid another lifter failure. I believe my mechanic has checked all the screens.

KevinRum · October 14, 2022

Hi RustyGunz, I am no mechanic so take my experience with a grain of salt. I can attest to having the exact same issue and no-one would grasp the severity of the massive amount of pressure I saw on my gauge. I swear if the gauge could read 100psi, it would be there and get there almost instantly when reaching 3000-3500rpm. My low side was around 25psi at <1000rpm when hot so the range of the sensor was not skewed per se. A new pressure sensor measured the exact same thing by the way as it was one of the first things I tried. Did I mention this was after a brand new Oil pump was installed so can't blame the issue on that. It wasn't until the 4th failed lifter (replaced all of them the first round) did my mechanic change the VLOM (and pressure bypass in the 2-stage oil pump housing/system - so he said). I don't know for sure if he actually changed the pressure bypass but the GMC Dealer mechanic I was also corresponding with was certain the high oil pressure was from the VLOM. When the new lifters failed, they were destroyed - mechanic said he never saw anything like it, even mentioned it looked like they exploded! Also, it was a different lifter every failure. Once the pressure subsided (always less than 80psi) , no more lifter failures.

I'm not sure which fixed the issue and my prior suggestion with the AFM bypass was because I felt every failure I had was due to the AFM trying to kick in and the VLOM too sluggish to respond in time. I thought it might save you from repeated failure until you saw that pressure go back to normal.

RustyGunz · October 14, 2022

18 hours ago, KevinRum said:

Hi RustyGunz, I am no mechanic so take my experience with a grain of salt. I can attest to having the exact same issue and no-one would grasp the severity of the massive amount of pressure I saw on my gauge. I swear if the gauge could read 100psi, it would be there and get there almost instantly when reaching 3000-3500rpm. My low side was around 25psi at <1000rpm when hot so the range of the sensor was not skewed per se. A new pressure sensor measured the exact same thing by the way as it was one of the first things I tried. Did I mention this was after a brand new Oil pump was installed so can't blame the issue on that. It wasn't until the 4th failed lifter (replaced all of them the first round) did my mechanic change the VLOM (and pressure bypass in the 2-stage oil pump housing/system - so he said). I don't know for sure if he actually changed the pressure bypass but the GMC Dealer mechanic I was also corresponding with was certain the high oil pressure was from the VLOM. When the new lifters failed, they were destroyed - mechanic said he never saw anything like it, even mentioned it looked like they exploded! Also, it was a different lifter every failure. Once the pressure subsided (always less than 80psi) , no more lifter failures.

I'm not sure which fixed the issue and my prior suggestion with the AFM bypass was because I felt every failure I had was due to the AFM trying to kick in and the VLOM too sluggish to respond in time. I thought it might save you from repeated failure until you saw that pressure go back to normal.

Thanks for the reply,

so now your oil doesn’t go right off the gauge? I’m having mental trouble pushing it to that level lol

I’m pretty sure my failure was from the cylinder 7 going into 4 cyl mode under load.
Starting to think the best solution is a for sale sign

KevinRum · October 17, 2022

Hi RustyGunz,

That is correct, the top pressure I now see is 75-78psi with petal to the metal. Low side is still the same before and after the high pressure situation. I am leaning more toward the new VLOM fixed that issue - I think the old one, despite testing fine, was a little sluggish not visible during static testing.

Technically the AFM should not activate under load so I don't know. I can say I babied my ride almost every time I got the truck back, very careful not to let the pressure get too high and still failed within 100miles every time. I too was looking hard at putting a for sale sign on mine but knew I would feel bad if it happened to the next person. With the price of new and used trucks, I just couldn't afford it this year. I even contemplated a trade in on another brand but it simply wouldn't stay running long enough to make that happen. I feel your pain and wish you the best whatever you do!

KevinRum · October 17, 2022

FYI: My Sierra did not have a screen under the pressure sensor, and according the the dealer and my VIN, it does not come with one. Changing the pressure sensor made no difference on anything.

RustyGunz · October 19, 2022

On 10/17/2022 at 7:30 AM, KevinRum said:

FYI: My Sierra did not have a screen under the pressure sensor, and according the the dealer and my VIN, it does not come with one. Changing the pressure sensor made no difference on anything.

So you changed the oil pump and the pressure never went above 78psi? I’d say mine hit 80psi once out of the last 5 times over 3500rpm. Usually stops at work the second last increment I. The gauge. Going to take it to the dealership to get a second opinion on this oil pressure