Normally I don't like to post these kinds of things where I ask people to help identify a problem based on a sounds, but this is a good friend's truck and he lives over an hour away from me. I had the chance to hear what he's been describing to me for a while. This noise occurs mainly when the engine is cold and usually completely disappears when the things are good and warmed up. Lately he said it is now somewhat intermittent when warmed up.

The sound can be heard on the passenger side in the engine bay. It can also be heard very clearly underneath the truck resonating from the exhaust pipe and also at the exhaust outlet. The exhaust pipe is NOT hitting or touching anything, plenty of clearance.

Sometimes I think it severe injector noise or a really loose rocker arm, but I really don't think so. Depends on where you are standing when observing the noise I guess. I have an educated guess as to what it is, but it's still a guess. I think he needs a turbo rebuild and/or the turbine is hitting the housing. I want to hear what you all think.

Truck runs perfectly fine otherwise. No oil consumption, no problems at all.

Last winter he was having a sticking EPBV and I walked him through unplugging it. I've given him photos, directions, and anything he needs to do to clean the EPB sensor and such but he's pretty nervous about DIY and is waiting for me to help; but I'm very busy lately.

The impeller was checked and it is not loose and feels like all the others I've felt.

 

Maybe the morning crowd has some comments.

 

Fan belt idler pulley.

 

x2 on tensioner/idler. Remove the serpentine belt, start it, and see if the noise is still there.

 

Thanks, I will check on that.

 

Idler pulleys and alternator bearings will often fail in that way-the noise will at first only be there when started cold. If the noise is ignored, the pulley gets hotter and the noise lasts longer until things come apart in an expensive way.
A good tool to use for troubleshooting this is a stethoscope while the belt is still installed and the engine is running cold.

 

Still trying to figure this out. Belt removed with no change. This hard to explain metallic, banging, squealing/howling sound is now more pronounced and is no longer intermittent, but always present. The owner is observing the noise under the engine and it sounds like it is coming out of the oil pan and the exhaust. Kind of everywhere down low, I guess.

Does this sound like I need to look at the turbine side of the turbo or is there not usually a clearance issue there? I'm kind of stumped, I know how to fix stuff if I know what it is that needs fixed. :-) And I really dislike throwing parts at something by guessing.