New here with a serious? Problem

[Dcshoeco87]

Hey guys! Names Bryan. I have scoured the Internet for days and haven't seen anyone with the exact problem I have. So here it goes

 

2006 gmc 2500 6.0l

262,000 miles

 

I start my truck every morning and let her run for 15 mins before work. (Live in New England). The truck runs perfectly fine with no noises. About 15 minutes of driving I I start to hear this "clacking" noise. It starts off quiet and becomes louder. It clacks with the revs of the engine (faster and slower). It sounds like a rod it about to

Shoot through the side of the block and you can hear it clear as day with the window down. Sounds like it's on the drivers side. Then after about 10 minutes it completely goes away for the rest of the ride to work (1 hour ride total). After it goes away the truck sounds completely smooth like nothing ever happend. I have a video of the noise I can post once I figure it out Anyone have this happen??

 

Thank you so much guys

[diyer2]

Piston slap?

[Dcshoeco87]

Wouldn't that happen when cold as well as hot? And or all the time?

[davester]

get a mechanics stethoscope to narrow down where the problem is and what frequency it is [if it's at engine speed, like a piston, or half-speed, like a valve/lifter/pushrod]

[Formulabruce]

You have a broken exhaust manifold bolt causing a leak... heat and expansion can change its sound and intensity. You may be able to get out the bolts broken with manifold off, but youll need new grade 8 bolts and COPPER "Never Seize" to do it right, with new gaskets. Good luck!!

PS the bolts may all seem to be there and in place ....

[citydriver]

If you don't find a problem with the exhaust manifolds, I would also check the flex plate/flywheel for cracks near the crank mounting bolts. They can usually be seen with an inspection mirror. the crack will appear to look like a rusty lightning bolt. That's the closest visual reference I can come up with.

[Dcshoeco87]

Its not the manifolds, that has a different sound (more of a tick). I'll double check the flywheel, the guy I got it from just had the transmission done last year (rebuilt). So I would of imagined they would have saw that. I ha e scope and flashlight in my truck so hopefully I'll pinpoint it. I don't know what it's worth but I felt the valve cover while

It was making the noise and I felt absolutely no extra vibrations. Also I put the scope to it while it wasn't making the noise and when I put it on the fuel rail and injectors it had the same sound.