Replaced afm lifters

[Mlstammerjr]

Hey all. So I had a collapsed lifter on my 09 Yukon. We replaced all of the lifters yesterday (8 regular and 8 AFM) after getting it all put back together, it started right up and ran fine until the engine got hot, then the oil pressure plummeted and you could feel the engine starving for oil. No check engine lights, oil is full on the dipstick. What could be causing this and what can I check to diagnose this.

Google ai (I know it’s not always reliable, but that’s why I’m here) says that the valley gasket is either bad or possibly not torqued to spec. We did replace the gasket but it’s a cheap gasket as it was all I could find in stock. My dad put the cover back on I honestly don’t know if he torqued it down to spec or not. I know he torqued the heads to spec and the exhaust manifold. I’m waiting on him to reply on whether or not he torqued that right.

But anyways , is that likely my issue or something else? Where should I start with diagnosing this?

 

[randeez]

how was oil pressure before swapping them all?
was there a failure or just trying to be proactive?
did you disassemble the entire vlom (afm actuators) from the underside of the valley cover? the gasket does come with the pedestal gaskets but kinda hard to mess up. and the perimeter gasket doesnt do anything for oil pressure

and welcome to tyf

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please. If we can't see it, it does not exist.

You are already receiving clarifying questions from the knowledgeable folks on this Forum.

When you say that the oil pressure plummeted, what was the psi reading from your oil pressure gauge at that point?

What was the oil pressure reading before your performed this work, when cold and at hot idle.

 

[Mlstammerjr]

how was oil pressure before swapping them all?
was there a failure or just trying to be proactive?
did you disassemble the entire vlom (afm actuators) from the underside of the valley cover? the gasket does come with the pedestal gaskets but kinda hard to mess up. and the perimeter gasket doesnt do anything for oil pressure

and welcome to tyf

The oil pressure was fine before mostly, it had intermittent issues with the oil pressure sensor, but no actual pressure issues, just the sensor going out. There was a lifter that had collapsed that was why we changed them. But it’s got an oil leak and I think it ran low on oil a few times, that’s why the lifter collapsed. It was misfiring before and you could hear it chattering, when we got it all back together the misfire was gone and no chattering. The oil pressure was fine until the engine heated up.we didn’t take apart the vlom at all

Thank you

 

[tooleyondeck]

Pick up tube o-ring, oil sending unit, oil pump itself, there are a few usual suspects but it sounds like you didn't touch the timing cover? Possibly did not delete the AFM system?

Could you clarify whether you retained or deleted the AFM system?

 

[Mlstammerjr]

K

Pick up tube o-ring, oil sending unit, oil pump itself, there are a few usual suspects but it sounds like you didn't touch the timing cover? Possibly did not delete the AFM system?

Could you clarify whether you retained or deleted the AFM syste

Pick up tube o-ring, oil sending unit, oil pump itself, there are a few usual suspects but it sounds like you didn't touch the timing cover? Possibly did not delete the AFM system?

Could you clarify whether you retained or deleted the AFM system?

I did not touch the timing cover and the afm system was still retained.

 

[rdezs]

Not too many people here repair the AFM system. Viewed as a ticking time bomb, moving forward with a delete after an AFM lifter collapse is the norm.

I do recall that GM says that anytime the VLOM is removed, it should be replaced.

Considering nothing else was touched, the most likely culprit is a leak under the VLOM plate. This posting reads like the gasket around the perimeter of the plate was replaced.... I don't think that's a real option. The integral gasket involves some disassembly to replace, also covers the oil towers in the middle of the valley. If you somehow just replace the perimeter, the new gasket will increase the height of the plate slightly.... And the existing seals over the towers won't be compressed enough.

I think a new VLOM plate is necessary, torque down properly. (With new OEM GM oil pressure sending unit with new screen underneath)

If you still have an oil pressure issue after that, then I would pull the pan, replace the pickup tube o-ring and the pressure relief valve mounted inside the oil pan on the driver side. While you're there you can remove the oil pump pressure relief spring and valve, make sure it's clean and not gummed up and sticking.

The best all around fix, however, is simply do the AFM delete for long-term reliability.

 

[Marky Dissod]

Not too many people here repair the AFM system.

No one should.

Viewed as a ticking time bomb, moving forward with a delete after an AFM lifter collapse is the norm.

Has been for at least 10 years now, and yet ...

I do recall that GM says that anytime the VLOM is removed, it should be replaced.
Considering nothing else was touched, the most likely culprit is a leak under the VLOM plate. This posting reads like the gasket around the perimeter of the plate was replaced.
I don't think that's a real option. The integral gasket involves some disassembly to replace, also covers the oil towers in the middle of the valley.
If you somehow just replace the perimeter, the new gasket will increase the height of the plate slightly, and the existing seals over the towers won't be compressed enough.

EXACTLY.

I think a new VLOM plate is necessary, torque down properly. (With new OEM GM oil pressure sending unit with new screen underneath).

Better yet, NOT a Variable Lifter Oil Manifold Assembly; see the above.

If you still have an oil pressure issue after that, then I would pull the pan, replace the pickup tube o-ring,
and the pressure relief valve mounted inside the oil pan on the driver side.
While you're there you can remove the oil pump pressure relief spring and valve, make sure it's clean and not gummed up and sticking.
The best all around fix, however, is simply do the AFM delete for long-term reliability.

Older the engine is, the less V4 mode saves fuel, and builds up carbon in the part time cylinders.
Engine reliability and longevity are best served by disabling & deleting Engine Half@$$.

 

[07burban88]

this is why i swapped to the 4.8. no AFM and i got the motor for like 300. but yes, delete the afm completely. its also possible the collapsed lifter damaged the cam

 

[Joseph Garcia]

K



I did not touch the timing cover and the afm system was still retained.

I would do what @rdezs suggests in Post #7 to replace the VLOM cover and associated gaskets, as that appears to be the most likely the root cause of your issue.

 

[Mlstammerjr]

Not too many people here repair the AFM system. Viewed as a ticking time bomb, moving forward with a delete after an AFM lifter collapse is the norm.

I do recall that GM says that anytime the VLOM is removed, it should be replaced.

Considering nothing else was touched, the most likely culprit is a leak under the VLOM plate. This posting reads like the gasket around the perimeter of the plate was replaced.... I don't think that's a real option. The integral gasket involves some disassembly to replace, also covers the oil towers in the middle of the valley. If you somehow just replace the perimeter, the new gasket will increase the height of the plate slightly.... And the existing seals over the towers won't be compressed enough.

I think a new VLOM plate is necessary, torque down properly. (With new OEM GM oil pressure sending unit with new screen underneath)

If you still have an oil pressure issue after that, then I would pull the pan, replace the pickup tube o-ring and the pressure relief valve mounted inside the oil pan on the driver side. While you're there you can remove the oil pump pressure relief spring and valve, make sure it's clean and not gummed up and sticking.

The best all around fix, however, is simply do the AFM delete for long-term reliability.

The vlom plate with all the components? Can you possibly get me a link to what you’re talking about ? And I know the afm delete is the better option…. Well I know now, but I didn’t at the time. I just need this thing running and I’m not trying to tear it all back apart right now lol, that was a lot of work.

 

[Mlstammerjr]

Not too many people here repair the AFM system. Viewed as a ticking time bomb, moving forward with a delete after an AFM lifter collapse is the norm.

I do recall that GM says that anytime the VLOM is removed, it should be replaced.

Considering nothing else was touched, the most likely culprit is a leak under the VLOM plate. This posting reads like the gasket around the perimeter of the plate was replaced.... I don't think that's a real option. The integral gasket involves some disassembly to replace, also covers the oil towers in the middle of the valley. If you somehow just replace the perimeter, the new gasket will increase the height of the plate slightly.... And the existing seals over the towers won't be compressed enough.

I think a new VLOM plate is necessary, torque down properly. (With new OEM GM oil pressure sending unit with new screen underneath)

If you still have an oil pressure issue after that, then I would pull the pan, replace the pickup tube o-ring and the pressure relief valve mounted inside the oil pan on the driver side. While you're there you can remove the oil pump pressure relief spring and valve, make sure it's clean and not gummed up and sticking.

The best all around fix, however, is simply do the AFM delete for long-term reliability.

I have all the gaskets for the vlom, admittedly we only changed the perimeter gasket because the rest of them looked fine, maybe that’s where we messed up

 

[Joseph Garcia]

I have all the gaskets for the vlom, admittedly we only changed the perimeter gasket because the rest of them looked fine, maybe that’s where we messed up

IMO, that is EXACTLY where you messed up.

General Motors does not explicitly require you to replace the VLOM (Valve Lifter Oil Manifold) cover itself simply for removing it, but GM does recommend replacing the VLOM gaskets and mounting bolts during reassembly.
Here are the critical details regarding removal and reassembly:

• The Gaskets are Single-Use: The specialized rubber or silicone gasket that seals the VLOM to the engine valley is designed to crush and conform to the surface upon its initial installation. Once removed, these gaskets will not spring back and are highly likely to leak.
• Torque-To-Yield (TTY) Bolts: GM advises against reusing the original bolts that hold the VLOM cover down. Replacing them with Genuine GM Engine Parts ensures you get a proper seal and avoids uneven clamping force, which can lead to oil pressure loss or internal leaks.
• 
  
• Servicing Lifters: If you are removing the cover to service or replace Active Fuel Management (AFM/DOD) lifters, it is common practice to replace the entire VLOM unit. Worn solenoids, internal leaks, or a clogged oil filter screen under the cover can cause unintended cylinder deactivation and lead to premature lifter failure.

 

[rdezs]

 

[j91z28d1]

I don't really agree that anything involving a volm can cause you to lose ALL oil pressure. you could run the truck without a volm installed and still get some pressure, just make a mess in the back where the sensor goes. but do agree the under vlom solenoids should be replaced if you're going to replace the afm lifters with new afm lifters. there's a theory that most afm failures are from the electrical side, not always hardware based. but impossible to tell really. plus all new parts are junk. so unless you used oem or millings afm lifters, which are very expensive, the new ones will ail agian and the "good" ones still might.

either way, there's no oil going to the afm system at idle, so nothing to leak, besides maybe a damage solenoid, but even then the ls oil pump has pretty good volume. low pressure yeah, but zero pressure is hard to believe.

I would check the oil pressure sensor again, it's probably dead. from there, check with a mechanical gauge on the side of the block. if you still have zero, it's gotta be the pump. even a broken o ring as a some pressure.

 

[Mlstammerjr]

I don't really agree that anything involving a volm can cause you to lose ALL oil pressure. you could run the truck without a volm installed and still get some pressure, just make a mess in the back where the sensor goes. but do agree the under vlom solenoids should be replaced if you're going to replace the afm lifters with new afm lifters. there's a theory that most afm failures are from the electrical side, not always hardware based. but impossible to tell really. plus all new parts are junk. so unless you used oem or millings afm lifters, which are very expensive, the new ones will ail agian and the "good" ones still might.

either way, there's no oil going to the afm system at idle, so nothing to leak, besides maybe a damage solenoid, but even then the ls oil pump has pretty good volume. low pressure yeah, but zero pressure is hard to believe.

I would check the oil pressure sensor again, it's probably dead. from there, check with a mechanical gauge on the side of the block. if you still have zero, it's gotta be the pump. even a broken o ring as a some pressure.

It never quite goes to zero though. It is about normal until the engine gets hot then it plummets down to like 2 or 3. If you give it a little gas it goes up to maybe 20-30. You can feel the engine starving for oil as well.

 

[rdezs]

I don't really agree that anything involving a volm can cause you to lose ALL oil pressure. you could run the truck without a volm installed and still get some pressure...

either way, there's no oil going to the afm system at idle, so nothing to leak...

Not correct.

Oil pressure sending unit is mounted in the VLOM, which is fully pressurized to the solenoids in the VLOM.

If there's not a good seal at the top of the oil towers under the VLOM....that's a huge oil leak. Even with solenoids closed at idle, pressure would come up from lifters and spray out under the VLOM.