6.0 rattle when cold

[makfisher]

i have a 2004 2500hd with the 6 liter and before the motor reaches temp there is a lose rattle radiating from the bottom end of the motor. this is not the typical piston slap like many other 6 liters. the rattle almost sounds like a loose heat shield or exhuast component. i checked all shields and components as well as the dealer and as of yet have not foud a solution. my dealer is looking into this and has deemed in NOT normal. any suggestions?

[Jester4736w]

Are you sure it's a rattle? Or could it be something inside? I cant picture a lose heat shield or something of that nature rattling till it gets warm, then stopping.

[SilveradoWV]

Seems like the same problem on my 8.1L, it usually does it 2 times right after start up cold.

[Jester4736w]

Oh ya know what? Now that you mentioned it i might have the same thing with my 03 hd... When i start it, seems like once i put it in reverse it makes a whinning sound, almost sounds like something is selfadjusting. wierd...

 

Not only in reverse and for only 2 seconds, then i never hear it again till i shut it off and let it cool overnight or for a while.

[makfisher]

it very well may be somthing in the motor it self. it just sounds like a loose heat shield. lasts for about 2 mins when cold then goes away. i got the old "we dont think it is anything serious but we are looking into it." from the dealer we will se what they figure out.

[SilveradoWV]

Well mine doesnt do it for 2 minutes, usually does it 2 times for about 1 second each time, mine does sound like a heat shield though.

[polarisboy]

Sure it's not a broken exhaust bolt allowing the manifold to leak slightly on startup until it warms up?? They make tick/rattle sound.

 

Broken bolts are very common with these.

 

Just a suggestion

[Mattt]

Mine has a full time rattle now. It started out as you said, very infrequent, and only when cold. On my truck its where the exhaust comes together mid ship. My truck has dual pipes into the muffler, one of the pipes has a bolt together flange, the other has a slip fit with a clamp around it. The rattle comes from the slip fit pipe. No matter how tight I get the clamp, I still have the rattle. I had it looked at by a dealer, the tech put on the R.O. "tightened clamp(poor factory design)"

 

This rattle really kicked into high gear once my truck was back from the dealer for exhaust manifold replacement/broken bolt extraction. They replaced the manifold under warranty and took care of the broken manifold bolts. Im looking for a permanent fix on this, hopefully someone here has one.

[rcpd34]

Sounds like the infamous Piston Slap. Sounds almost like a diesel right? My 8.1 does it too; not my 6.0 though. GM won't do a thing for you. BTW, I had BOTH exhaust manifolds replaced under warranty and even got a new head because the snapped off the bolts & couldn't gety 'em out.

[Dupesy]

My '04 does it too. It's a high pitched rattle, that stops as soon as the engine begins to get warm. Usually right after I pull out of the driveway. Although, I haven't noticed it now that it's gotten to colder weather. It definitely sounds like a rattle, too sharp and high pitched for piston slap, I would think. Especially with only 33,000 on the truck.

[Jester4736w]

Dupesy... From what i've been hearing on here piston slap has no remourse, lol... I guess the 6.0's do it even with say 4500 miles on it. I've learned to just ignore it i guess, still concerns me a little bit though.

[Dupesy]

I did some more research on here about it, and it does sound like mine des have the piston slap as well, but ti doesn't seem to do it all the time. I have noticed that "diesel" sound before. But, most of time it doesn't do it. I'll speak to the dealership about, maybe I'll get a extended warranty of the engine, didn't someone here get that? Now, back to the rattle....

[Jester4736w]

I usually only hear the piston slap when i first start it, or when it's in high gear working up a hill.... Other than that dont hear it really ever.

[redbugdave]

I just got an 06, 6 liter and mine does the rattle also, when cold. It does sound like a loose heat shield...or a loose bearing without grease, type of sound. I've got less than 600 miles on it. I plan on crawling underneith and isolating it. It is in the lower middle portion of the truck, like the transmission area...not the upper engine area. It goes away once things gets warmed up a bit. You think it's normal or else there would be a tech bulletin out on it...

[redbugdave]

This morning when starting up to go to work, I took the flashlight and crawled underneith when I first heard the rattling. It quieted down when I put my hand on the stretch of exhaust pipe before the catalitic converter. Mostly from the crossover pipe coming from the drivers side to the passenger side. I think it is in the mounting bracket holding the converter and pipes. So...at least it's not piston slap, manifold bolts, etc. After checking it out, I think it is nothing to really worry about, just a little play in a system designed to expand and contract with heat cycles. It warms up a little bit, the tailpipe expands, and things quieten up. But, I would rather not have to hear it on a cold morning, seems GM could have figured it out when designing the system.

 

Dave