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Broken Pushrod... Now a big repair

DENALIHD66

By DENALIHD66
in Engines & Drivetrain

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DENALIHD66 Enthusiast

DENALIHD66

Posted
Posted

Here's the backstory (from what I think).  My truck has had a noisy lifter for a couple years now.  Never thought much of it.  Fired up the truck the other day and the ticking noise was VERY apparent.  I recorded a video of the ticking.  A few minutes later, it starts misfiring and shaking, and CEL and stabilitrack lights came on.  Got it scanned, cylinder 4 was misfiring.  Not a big deal right, so I drove it 30 miles to the dealer for service.  It was a pretty harsh ride when under any load, shaking quite a bit.

 

Diagnosis: broken pushrod (total of 8 rods need replaced) and an "LVL Manifold" that I cannot find any information on because I've never heard of such a thing.  Its not the intake manifold, but it was the issue for why there was oil leaking into cylinder #4 (gaskets also getting replaced).  I asked about the plugs, they were all fine, and the one with oil was cleaned off. 

 

Can anyone weigh in on what this manifold thing is they are talking about?  Btw this is for a 6.2L with only 57,000 miles on it.

 

Mods: CAI, Borla exhaust, Blackbear tuned.

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It's Tim
It's Tim

Don't beat on it.

DENALIHD66
DENALIHD66

Afm is a joke.  It doesn't actually save MPG except for the controlled Epa test so they can market +1 mpg.  But the issues and costs are pushed to the consumer for its failures

newdude
newdude

VLOM.  Valve Lifter Oil Manifold assembly.  Its the center valley plate in the engine.  The plate consists of oiling passages to 4 solenoids, the oil pressure sensor and filter screen and wiring.  ECM

Posted Images

papageoff Enthusiast

papageoff

Posted
Posted
19 minutes ago, stevejones said:

VLOM manifold, maybe?

I was just trying to remember the name of it, but yeah... It's probably that.  The VLOM is the part that handles the oil distribution to the AFM system.

DENALIHD66 Enthusiast

DENALIHD66

Posted
  • Author
Posted
Just now, papageoff said:

I was just trying to remember the name of it, but yeah... It's probably that.  The VLOM is the part that handles the oil distribution to the AFM system.

Okay cool thanks.  By disabling AFM with my tune about 10k miles ago would that have messed it up? I disabled it to avoid having issues associated with AFM

papageoff Enthusiast

papageoff

Posted
Posted (edited)
6 minutes ago, DENALIHD66 said:

Okay cool thanks.  By disabling AFM with my tune about 10k miles ago would that have messed it up? I disabled it to avoid having issues associated with AFM

I'm not sure, honestly.  It's probably being replaced out of an abundance of caution but it could have been damaged when a pushrod broke, I suppose.  

 

As for disabling AFM, my understanding is that an electronic disabling doesn't fully solve the issues with AFM because the parts are all still there.  You have to do a full delete (replace the lifters, cam, remove the VLOM, and tune it out. to truly avoid AFM problems altogether.  That said, I have no idea if the AFM system was involved in your failure.  It might be considering what you describes sounds very similar to what mine did when an AFM lifter died on me.  If so, they'd probably be replacing the VLOM as a part of that job.  I know they did change mine.

I'm looking at doing a delete because I'm running out of extended warranty this year and don't want to pay for an AFM repair if it happens to me again.  The parts for the delete can be had for less than 1k and the repair bill (warrantied at the time) was 4k+.

Edited by papageoff
papageoff Enthusiast

papageoff

Posted
Posted
Just now, papageoff said:

I'm not sure, honestly.  It's probably being replaced out of an abundance of caution but it could have been damaged when a pushrod broke, I suppose.  

 

As for disabling AFM, my understanding is that an electronic disabling doesn't fully solve the issues with AFM because the parts are all still there.  You have to do a full delete (replace the lifters, cam, remove the VLOM, and tune it out. to truly avoid AFM problems altogether.  That said, I have no idea if the AFM system was involved in your failure.  It might be considering what you describes sounds very similar to what mine did when an AFM lifter died on me.  If so, they'd probably be replacing the VLOM as a part of that job.  I know they did change mine.

I'm looking at doing a delete because I'm running out of extended warranty this year and don't want to pay for an AFM repair if it happens to me again.  The parts for the delete can be had for less than 1k and the repair bill (warrantied at the time) was 4k+.

Oh, and I had to wait a month for the parts to come in.  That was fun.

stevejones Enthusiast

stevejones

Posted
Posted (edited)

Details on your maintenance, please.  What oil & filter did you use, frequency of OCI, own it since new?, etc.

 

Just trying to glean anything that will help my 5.3 avoid this...

Edited by stevejones
DENALIHD66 Enthusiast

DENALIHD66

Posted
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Posted
35 minutes ago, stevejones said:

Details on your maintenance, please.  What oil & filter did you use, frequency of OCI, own it since new?, etc.

 

Just trying to glean anything that will help my 5.3 avoid this...

Mobil 1 filter,  mobil 1 full synthetic changed every 7k miles.  Throttle body cleaned at 50k miles but was barely dirty

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
1 hour ago, DENALIHD66 said:

  My truck has had a noisy lifter for a couple years now. 

 

43 minutes ago, DENALIHD66 said:

  By disabling AFM with my tune about 10k miles ago would that have messed it up?

I disabled it to avoid having issues associated with AFM

No. Disabling the AFM 10K miles ago after the damage started years ago is a clue.

 

They are replacing the VLOM because the screens within it are not serviceable and are plugged...varnish....sludge or because testing has shown one or more solenoids (rare as hens teeth) have failed. 

39 minutes ago, papageoff said:

As for disabling AFM, my understanding is that an electronic disabling doesn't fully solve the issues with AFM because the parts are all still there.

Correct. In addition and something not spoken of often is the non AFM lifters also can and do fail. The mode of failure is different but fail they do. Under or over oiling. Secondly all failures are not 'design' related. Heat treatment failures happen as well. Another failure mode that gets blamed on the fact the AFM is even there. 

1 hour ago, DENALIHD66 said:

Diagnosis: broken pushrod (total of 8 rods need replaced) and an "LVL Manifold" that I cannot find any information on because I've never heard of such a thing.

 Damaged or just part of the TSB?  

1 minute ago, DENALIHD66 said:

Mobil 1 filter,  mobil 1 full synthetic changed every 7k miles.  Throttle body cleaned at 50k miles but was barely dirty

Here's where evidence and confidence butt heads. 

 

Evidence: Plugged VLOM screens the result of oil maintenance

VS

Confidence: Mobil 1 being good for 7K mile OCI's.

 

And I'm not picking on Mobil 1 but on the limits of all DEXOS 2 licensed oils in AFM applications. 

 

Disclaimer: IMHO

 

 

DENALIHD66 Enthusiast

DENALIHD66

Posted
  • Author
Posted

Afm is a joke.  It doesn't actually save MPG except for the controlled Epa test so they can market +1 mpg.  But the issues and costs are pushed to the consumer for its failures

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DENALIHD66 Enthusiast

DENALIHD66

Posted
  • Author
Posted
11 minutes ago, Grumpy Bear said:

 

No. Disabling the AFM 10K miles ago after the damage started years ago is a clue.

 

They are replacing the VLOM because the screens within it are not serviceable and are plugged...varnish....sludge or because testing has shown one or more solenoids (rare as hens teeth) have failed. 

Correct. In addition and something not spoken of often is the non AFM lifters also can and do fail. The mode of failure is different but fail they do. Under or over oiling. Secondly all failures are not 'design' related. Heat treatment failures happen as well. Another failure mode that gets blamed on the fact the AFM is even there. 

 Damaged or just part of the TSB?  

Here's where evidence and confidence butt heads. 

 

Evidence: Plugged VLOM screens the result of oil maintenance

VS

Confidence: Mobil 1 being good for 7K mile OCI's.

 

And I'm not picking on Mobil 1 but on the limits of all DEXOS 2 licensed oils in AFM applications. 

 

Disclaimer: IMHO

 

 

There is a TSB for rod replacement?  Service tech indicated to me they were damaged.  I think this was a fluke breakdown and once repaired I should be good.  You mentioned under or over oiling.  Can you elaborate a bit more?  I fill mine to where it is basically perfect in the center of the range found on the dipstick.  Is it better to fill it closer to the top line?

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
13 minutes ago, DENALIHD66 said:

There is a TSB for rod replacement?  Service tech indicated to me they were damaged. 

I don't know if it is a part of the TSB. Why it was a question.

 

https://www.enginebuildermag.com/2019/02/melling-tech-tips-for-gm-ls-lifter-issues/

 

While this video is for the previous motor series they share the same VLOM/Lifter assemblies and control type. It will answer some of your questions. 

 

16 minutes ago, DENALIHD66 said:

  You mentioned under or over oiling.  Can you elaborate a bit more?  

Hydraulic lifters 'pump' oil during operation. They have an internal check valve. It at times fails altering then normal action. I would expect the 8 pushrods he is replacing are the 8 that are in the AFM positions. Not related to this condition. Offered as additional information. 

 

26 minutes ago, DENALIHD66 said:

  I fill mine to where it is basically perfect in the center of the range found on the dipstick.  Is it better to fill it closer to the top line?

Yes. Full it good. 

27 minutes ago, DENALIHD66 said:

  I think this was a fluke breakdown and once repaired I should be good.  

Told you the evidence would be ignored. ? 

 

Enjoy the day

newdude Senior Enthusiast

newdude

Posted
Posted (edited)

VLOM.  Valve Lifter Oil Manifold assembly.  Its the center valley plate in the engine.  The plate consists of oiling passages to 4 solenoids, the oil pressure sensor and filter screen and wiring.  ECM controls the VLOM and commands the solenoids to open and close oil flow to cylinders 1, 4, 6 and 7, the AFM cylinders. 

 

When in 4 cylinder mode, oil is supplied by the VLOM solenoids to each of the AFM lifters.  The oil pressure applies to the locking pin in the lifter, causing the pin to unlock letting the lifter "collapse" and deactivate the cylinder.  When returning to V8 mode, the solenoids close oil pressure to the lifters, allowing the pins to lock back in place and the 4 AFM cylinders to begin functioning normally again.

 

What sounds like that happened to your engine is the solenoid in the VLOM failed on a cylinder and sent oil to the lifter when it wasn't supposed to.  Then the solenoid returned to V8 function wrongly timed, causing the lifter to re-engage at the wrong moment (think compression stroke when the valves are closed), and thus bending the pushrod.   

 

Not the first time I've seen this at work.  Seen a couple get lucky with just a new pushrod, others get torn down for AFM lifters, a VLOM and pushrod.  Just had a 5.3 two weeks ago in for a miss.  Tech found a bent rod on #4.    

 

GM LS Lifter Issue, Melling JB-7011 Tech Tips - YouTube

 

Quote

 

#15-06-01-002K: Engine Misfire/Tick Noise, Malfunction Indicator Lamp (MIL) Illuminated - DTC P0300 Set - (Dec 17, 2020)

Condition

Some customers may comment on a malfunction indicator lamp (MIL) on and/or an engine misfire/tick noise.

Technicians may find DTC P0300 set or in history.

Cause

This may be caused by one of the following conditions:

  • Active fuel management (AFM) lifter that is mechanically collapsed and/or stuck all of the time.
  • Internal locking pin damage in the lifter, due to oil aeration.
  • Lifter that has collapsed and is stuck in the lifter bore.
  • The engine may have a bent push rod.
Correction

Note: Inspect the camshaft for damage while the lifters are removed from the engine. If damage is found, replace the camshaft per SI.

If SI diagnosis does not isolate the cause of this concern, technicians should inspect for valve operation.

If the valve(s) are not moving, replace the valve lifter oil manifold and affected bank of AFM lifters. Refer to Valve Lifter Oil Manifold Replacement and Valve Lifter Replacement in SI.

If the lifter has spun the bore, the guides should also be replaced.

 

 

Edited by newdude
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