2008 5.3 Silverado valve train noise...???

I got a 2008 Silverado 4x4 1500 with the flex fuel 5.3.
Driving into work yesterday I started hearing a series of clattering and wondered what it could be.
I first thought vibration or wind rattling heat shield on exhaust.
But it happened over and over again.
Last a second or two, stop, 30-40 seconds later it would do it for a second or two, repeat.
I was on highway 75-80 and pretty flat road.
My ride is 60 miles each way and this happened about 1/2 way into it.
Did it for the last 10-15 miles as I drove to work.
Then the first 20-25 miles on my way home and quit.
I began wondering if it was "displacement on demand"?
I am not even sure if this motor is equipped with it, but the way it happened made me wonder if there were lifters being "de-activated", it didn't work as it should, then they pumped back up-activated again-"turned back on" or how ever these operate.
Is there such a thing that happens???
Would a 2008 5.3 truck motor have the d.o.d.?
I checked oil level, good, and changed oil about 600-700 miles ago now.
This morning all was good.
Any other similar known issues or anything I can look at or for???
Appreciate whatever I can find out.
THANKS for any help or info ! ! !

Sounds like a lifter trying to stick or needle bearings trying to go bad in lifter roller

I will bring this back up and ask some more again...
The slight tick that used to happen had went away for quite a while.
The truck has sat for some long spells.
Got drove a couple days in a row a week ago and now CLATTERS loud.
Sounds like a lifter hammering.
Wondering if there is an issue with the d.o.d. set up.
Been googling and reading about some issues and hoping I can get it quiet without tearing to much down.
See that there is a small oil filter inline with the d.o.d. system that sounds like something that can be an issue.
Any other "easy" solutions before I get too carried away???
Appreciate any help, advice, or tips...
THANKS

Looking at it again this past weekend and it is still noisy !!
I see that there are more studs missing than what is left on the exhaust manifolds.
Used to have a slight exhaust leak that you could hear cold and would quiet down as it warmed.
No doubt that it needs new studs and/or shorty headers, BUT...
It sure does sound like an internal noise/valve train.
HATE the thought of screwing around with the exhaust to find out it needs motor tore down and a lifter.
I had an older Expedition that "fooled" me a few years back.
I thought it had same type of clatter like a cam follower, turned out exhaust leak.
Just wondering if anyone else been here, done that now.
Check engine light on and see #4 cylinder mis fire along with O2 sensor codes EVAP pending
I pulled #4 plug and cleaned it up.
Has seemed OK since and after clearing codes.
2nd scan showed just EVAP P0449 and P0036 O2 sensor which has been on since I owned
Wondering does the #4 misfire relate to DOD at all?
Seems like noise loudest in that area too...

THANKS AGAIN

P0036 bank 1, sensor 2. Post CAT. - check the harness and the o2 sensor, swap it over to the other side, clear codes and see if the code transfers to the other side or stays. If it stays bad o2 sensor or you may need to look further up the harness to see if it's broken or melted.

Get a long metal bar or screw driver and place it on the heads to listen while it runs. Switch between the heads and other metal spots to listen for noise out of the ordinary. Even go under and listen to the oil pan too.

You may have to idle it up a bit to hear/locate it.


have you pulled the oil filter and open it up yet?

Need to look for metal flaking or chunks. If a lifter has gone enough it will take out the cam.

You could pull the valve covers off and try to move each rocker up/and down to see if one is loose? If so you have a collapsed lifter/bent push rod.



As much as they are a PITA to do you need to get the exhaust close up, it can also be the cause your O2 codes.

I figure that I am going to have to dig a little deeper, but thinking exhaust may be the first route I go.
Talked to co-worker and neighbor who told same tale.
Sounded like rod knocking or valve train noise when their exhaust leak got so bad.
Codes aren't worrying me much.
Had lights on since I got it years ago.
Don't mind putting it up for sale like that.
But can't see anyone interested the way it clatters now.

THANKS

https://www.youtube.com/watch?v=6vLcX_ccIFI

Mine seems to be running OK.
Hitting all the cylinders as it runs.
Just the loud clatter, which I am now suspicious is actually exhaust manifold(s) slapping the heads with so many studs missing.
Planning to get underneath and look better to see if I can find and feel puffing where worst leaking is.
If doesn't seem obvious enough may do the compression check as in video-Thanks for that too:)

For the broken exhaust studs, there is a simple fix via a bracket that bolts to the head and then clamps the manifold. I purchased two on Amazon for our '07 Suburban as the front stud on the passenger side and rear stud on the drive side are both broken. The passenger side install took maybe 10 minutes (I chased the threads just to be safe) but I have not yet tackled the driver side as access is damn near non-existent.

Appreciate that.
BUT...
leaky exhaust moved down my list of concerns yesterday.
Was planning to double check and make sure that was my noise before going to get studs and pull manifolds.
Just couldn't convince myself that was the main cause or cause of noise.
Can still hear the exhaust leak, but sounded like an internal knocking.
Bit the bullet and pulled passenger side valve cover.
The rocker for #4 was loose.
Rear most one.
Closer to firewall.
Didn't really pay attention, but think that is exhaust...?
But looks like a lifter there that just isn't pumping up.
Not a ton of room, maybe 1/16" to 1/8" travel between push rod end and valve stem.
Pulled the rocker off and a couple others just to compare.
It wasn't perfect, a little wear within needles at fulcrum.
I pulled it apart and packed some grease around the needles just to see if it would help or quiet that at all since other rockers seemed a little bit tighter there.
REALLY not wanting to get into this as I have been hoping to sell it for quite a while now.
One issue after another every time I get close to having it presentable and running well.
Any tips, tricks, or advice at this point.
Pulling the intake is more than I want to invest.
Is the #4 cylinder one effected by the D.O.D.??
Saw some stuff online about a small filter on top of the intake for the D.O.D. oil pressure feed.
Wondering what else might get the lifter to operate again.
Blow compressed air down the push rod center...? Maybe knock debris loose that is clogging?
Light tap on end push rod? Jiggle something loose?
Had ran well and MUCH quieter up until the short time ago when this started.
Hate to give it away and sell so cheap with it sounding like this, but really have a TON of other stuff I should be giving attention too.
BIG THANKS if anyone has anything...APPRECIATE IT ! ! !

I have seen a lot of bulletins similar to this one...

https://www.melling.com/wp-content/u...s-3.1.18-1.pdf

Shows:"The AFM activation and deactivation is controlled by the Valve Lifter Oil Manifold or VLOM.
The VLOM consists of 4 electronically operated solenoids and is bolted to the top of the engine
block beneath the intake manifold assembly."

Guessing that intake would have to be removed to get at this...?
Anything on the outside that might need attention?
Anyone have diagram of the controls for the D.O.D. or anything?
Hating this noise ! ! !