04 Denali rattle can sound around 800-1200 rpms

[DenaliJJ]

hey guys. New to the forum here and this is my first post. I recently purchased a 04 Denali xl that needed a fuel pump. So I replaced it with a Delphi and all is well there. Had an issue with a whirling noise heard at idle so I loosened belt and spun the stationary idler. Replaced and all is well. Now I have this noise at start up that sort of sounds like a ball bouncing around in a can for around 20 secs at idle. Seems to fluctuate in pitch and rythem if that makes any sense. After a bit it goes away. When I lightly touch the gas pedal I get to around 800 rpm and it starts the vibrating rattle clanking noise up to around 1200 and then i can't hear it until I let off gas and it gets back down to 800 for and dissapears after it's back down Around 5-600 rpm. I'm left thinking it's either the tensioner vibrating or possibly flywheel cracked. The reason I think it's not inside the motor is because I can hold the gas to where it starts making noise and it variates while holding steady at right around 1000 rpm. Oil pressure is right around 40 at start up and after a good hour or so of running it's anywhere from around 20-25 at idle in gear. Any ideas where to start? Sorry for lengthy post but I wanted to be as thorough as possible. Thanks in advance!

 

[Danny3737]

Can you post a video with the sound?

 

[Fless]

Might want to check the cat shields to make sure they're not loose. Those things can make some racket at various RPMs!

 

[DenaliJJ]

Yes I will try and upload a video here yet tonight via YouTube

 

[DenaliJJ]

Went to check the heat sheild and and there isn't anything around either one

 

[DenaliJJ]

 

[DenaliJJ]

With this noise it's not as evident in early morning start ups. After it warms out side or engine runs awhile it's heard on start up worse( short video) any ideas where to start or hell maybe it's an exhaust leak. I'm stumped

 

[06Escalade]

I had a similar issue recently. It was broken catalyst rattling around inside the y pipe. Depending on how much exhaust was passing through the pipe I would hear it. Enough "wind" to make that chunk of catalyst rattle around I guess. I won't be playing with additives like Seafoam ever again.

 

[06Escalade]

Replacing that catalyst y pipe was an amazing difference in the performance of the truck. Breathing out gives better gains than breathing in, thats for sure.

 

[DenaliJJ]

Replacing that catalyst y pipe was an amazing difference in the performance of the truck. Breathing out gives better gains than breathing in, thats for sure.

Where you able to hear anything when you smacked the pipes?

 

[06Escalade]

No, never tried that. I was afraid I could hurt the cat doing that. I had someone rev engine while I listened underneath

 

[06Escalade]

It was dark out when I recorded this. Noise was near start and near end. Was one of the cats disintegrating

 

[DenaliJJ]

I'm going to change the oil today and look for any metal or chunks of gunk in the filter I notice it has a cheap filter and about half a quart low so in goes mobile 1 5w-30 syn and a wix

 

[DenaliJJ]

It was dark out when I recorded this. Noise was near start and near end. Was one of the cats disintegrating

I tried listening under the vehicle today and my damn exhaust is to loud to really hear anything when it revs

 

[06Escalade]

Also, check and make sure all your exhaust manifold bolts are in place. I had one rust off, needed to seal exhaust manifold with a aftermarket clamp.

 

[DenaliJJ]

Well I changed the oil and it now sits around 45 at idle and a tad under after it's warm. Makese real nervous with the change in pressure from before. Also there was a tad bit of shavings on the drain plug. The motor was replaced by GM dealer in 2012 and has around 65k on the remaned engine. It was replaced due to a cam bearing being spun. Really hope this isn't the issue again. The noise isn't heard inside the car while driving and really only there at start up and rears its head again around that 1k mark. All the exhaust manifold bolts seem to be in place and it honestly seems to be coming from near the oil pan area underneath

 

[DenaliJJ]

New video from underneath

 

[06Escalade]

IMO thats the engine. I'm hoping its piston slap, not something else. Let the M1 marinate, see what happens M1 tends to be a bit noisy, but its a great cleaner oil.

 

[DenaliJJ]

IMO thats the engine. I'm hoping its piston slap, not something else.

My thoughts too. Funny thing is I can't hear it when someone revs it up past 1200 though. You would think somethin motor related would be louder through Rpms right? What's the easiest way to check the flexplate?

 

[06Escalade]

Piston slap occurs when the oil just starts to flow and the engine is cold. As the engine warms up and oil pressure increases, the piston tightens up in the cylinder. I say wait, see what M1 does. May take an oil change or 2 to get results. These engines go 300k if minimally maintained, so when I hear changing engines, then the next engine has issues it makes me wonder about prior owner maintenance. Also you may want to consider an oil test from blackstone. Its only $28. Like a blood test, tells you whats going on in the engine.