Guys I need help figuring out this engine rattle

[Dustin Jackson]

Hey guys I think it has come time for my Tahoe for a AFM lifter delete. I think I am having a lifter failure but this sounds different from other videos I've seen. Someone said the pushrod might be out of place causing this sound?

What do you think?

 

[Doubeleive]

does not sound good to be honest, the 1st thing you want to do is take the belts off both serpentine and ac to rule a external source in or out.
you are safe to start it up with no belt for a few seconds
do that and report back

 

[FasterBass]

does not sound good to be honest,

Understatement of the year right here. Sounds more like a rod knock...how many miles on the motor?

 

[Dustin Jackson]

@Doubeleive Sound comes from under driver valve cover

@FasterBass About 179,000 miles

 

[Dustin Jackson]

@swathdiver Where can I find a L33 camshaft? I am using part number 12583623 and am not having much luck finding a good seller.

 

[swathdiver]

@swathdiver Where can I find a L33 camshaft? I am using part number 12583623 and am not having much luck finding a good seller.

WorldPartsDirect on Ebay has them as does GMPartsGiant after a quick look. Getting scarce it seems.

 

[Dustin Jackson]

@swathdiver Thank you for that, I am going to look into getting that cam. Can you take a look at this parts list from Texas Speed to make sure I have everything selected correctly? This will be a for a 08 5.3.

 

[rockola1971]

Wow that sounds bad. Id verify that aint a rod knocking! Pull the valve covers and verify you dont have a rocker arm worn out at its pivot too!

 

[iamdub]

Hey guys I think it has come time for my Tahoe for a AFM lifter delete. I think I am having a lifter failure but this sounds different from other videos I've seen. Someone said the pushrod might be out of place causing this sound?

What do you think?

That sounds worse than just a ticking (weak/collapsed) lifter. That sounds like it's bouncing around in there. Could be really messed up, turned, maybe busted lifter tray. Or, maybe the lifter is just collapsed and that's the push rod bouncing around. Have a misfire or rough idle? Any DTCs?

You'll have to at least pull the cover to find which cylinder and assess. To really know the extent, pull the head. Then you'll know if a standard AFM delete would fix everything or if the engine will need more work.

 

[Dustin Jackson]

That sounds worse than just a ticking (weak/collapsed) lifter. That sounds like it's bouncing around in there. Could be really messed up, turned, maybe busted lifter tray. Or, maybe the lifter is just collapsed and that's the push rod bouncing around. Have a misfire or rough idle? Any DTCs?

You'll have to at least pull the cover to find which cylinder and assess. To really know the extent, pull the head. Then you'll know if a standard AFM delete would fix everything or if the engine will need more work.

@iamdub I agree, doesn't sound like anything I've seen online but the sound is coming from the top end. I plan on pulling the heads off this weekend to find the answer here but I want to get the parts ordered as soon as possible. If I find the damage it outside my scope of ability to repair and I have to return the parts, so be it.

p0306 cylinder 6 misfire is the only code

 

[iamdub]

@iamdub I agree, doesn't sound like anything I've seen online but the sound is coming from the top end. I plan on pulling the heads off this weekend to find the answer here but I want to get the parts ordered as soon as possible. If I find the damage it outside my scope of ability to repair and I have to return the parts, so be it.

p0306 cylinder 6 misfire is the only code

Hmmm. #6 is an AFM cylinder, but on the RH bank (passenger side). Looking forward to updates.

 

[swathdiver]

@swathdiver Thank you for that, I am going to look into getting that cam. Can you take a look at this parts list from Texas Speed to make sure I have everything selected correctly? This will be a for a 08 5.3.
View attachment 372865

I didn't see a part number for those lifter trays. Make sure they are GM OE and settle for nothing else unless tie bars. Everything else looks good. Which lifters are best?

 

[Geotrash]

@iamdub I agree, doesn't sound like anything I've seen online but the sound is coming from the top end. I plan on pulling the heads off this weekend to find the answer here but I want to get the parts ordered as soon as possible. If I find the damage it outside my scope of ability to repair and I have to return the parts, so be it.

p0306 cylinder 6 misfire is the only code

Lifter sounds often transmit through the pushrods and can sound like they're coming from the top end.

What's different about yours though is that the frequency is faster than camshaft rotation and seems to match crankshaft rotation speed. Let us know what you find when you pull the heads. Also, I would consider getting the ARP head bolts (bolts, not studs). They're reusable and can be torqued directly to full value, instead of torque-to-yield. They also make exhaust manifold bolts, which is what I used also.

 

[George B]

What's different about yours though is that the frequency is faster than camshaft rotation and seems to match crankshaft rotation speed.

I agree with this and am beginning to wonder if a piston skirt may be broken.

 

[FasterBass]

I agree with this and am beginning to wonder if a piston skirt may be broken.

Hence my rod knock comment. Way too fast for the cam.

 

[George B]

Hence my rod knock comment. Way too fast for the cam.

And its a sort if a dead knock not a tick. Like a piston hitting the head.

 

[Dustin Jackson]

I appreciate everybody's input. This is pretty stressful for sure. This weekend I am going to try to get the heads off and taking everybody's thoughts into consideration while I am digging for answers.

Today I am going to disable my fuel pump and turn the engine with the starter to see if I can replicate the sound. From there I will take the heads off this weekend and do the same thing. If I can produce the sound while turning the engine with the heads removed then well... that would be outside of my ability to repair it because the problem is in the bottom end somewhere and probably looking to get a new engine.

I am hoping that pulling the heads I will find some problems with the lifters, push rods, or valvetrain. I will also inspect the cylinder walls for damage like some have suggested the piston being the source of noise.

I appreciate everyone's support in this, if you have any other useful advice that would be great. This was a great running Tahoe until the day this happened, crazy how things go sometimes.

 

[George B]

I appreciate everybody's input. This is pretty stressful for sure. This weekend I am going to try to get the heads off and taking everybody's thoughts into consideration while I am digging for answers.

Today I am going to disable my fuel pump and turn the engine with the starter to see if I can replicate the sound. From there I will take the heads off this weekend and do the same thing. If I can produce the sound while turning the engine with the heads removed then well... that would be outside of my ability to repair it because the problem is in the bottom end somewhere and probably looking to get a new engine.

I am hoping that pulling the heads I will find some problems with the lifters, push rods, or valvetrain. I will also inspect the cylinder walls for damage like some have suggested the piston being the source of noise.

I appreciate everyone's support in this, if you have any other useful advice that would be great. This was a great running Tahoe until the day this happened, crazy how things go sometimes.

Good luck and keep us posted.

 

[Dustin Jackson]

Here is another video I took this morning, focusing on the passenger side. The sound definitely is stronger coming from passenger side.

Here it is after I gave it a couple revs. I guess it's hard to tell where the sound is coming from top or bottom.

 

[Geotrash]

Here is another video I took this morning, focusing on the passenger side. The sound definitely is stronger coming from passenger side.

Here it is after I gave it a couple revs. I guess it's hard to tell where the sound is coming from top or bottom.

2nd video makes it sound much more like valvetrain noise. Good luck getting the heads off and finding your smoking gun. We'll be here when you need us. :-D