Do the 3rd gens suffer cracked manifolds?
 

Been trying to track down a odd turbo-related "whistle" that I've had for about 50k. Dawned on me that it might resemble a noise a cracked manifold might produce. Not sure if my pyro is accurate, but I have seen 1600 before, and routinely see 1200 plus (the reason I question the accuracy). Are the 3rd gens plagued by the cracked manifolds?

The noise I have seems temperature related (engine temp, not air temps)....

Thoughts?

Louder when cold? Turbo wheels look good? black soot streaks anywhere?

The turbo is in good condition...

The last manifold crack I saw had a white residue underneath, where you couldn't see it (until removed).

I was told by a Dodge guy that the only time he has seen one crack it had been drilled for a pyro.

I have a pyro, but no cracks nearby...first place I looked.

Yes the 3rd gen manifolds crack,I normally see it happen at higher miles than the 2nd gens and usually on trucks that make a living towing heavy

Drove 1000 mile yesterday...there is no definitive reason why it does it or when it does it.

Drove most of the day through South Dakota, and it never did it. Got into some hills in Wyoming, and it did it twice pulling hills; but at different times and not back to back.

Then I thought about a comment someone made about air density...ok, it was damp and raining in parts of SD, and it was damp and raining in parts of WY. Temps hovered right about 50 to 60 degrees. I question this theory because it started happening right after the injectors were replaced...at about 180k.

I checked the turbo for play on Saturday, and it has no appreciable movement in any direction. And the manifold looks fine from the vantage point of it still being in the truck.

Do you have a boost gauge? Mabey you have a intercooler boot with a pin hole or something like that

My boost gauge is digital, so its probably not as good as a analog...but it doesn't fluctuate that much.

I would have thought if it was a "mechanical" failure, it would do it all the time? Like a pinhole in a boot...should whistle all the time right? I'm going to look at two things, one of which would have been taken off to replace the injectors...the intake horn. Maybe a gasket didn't get seated?

I'm assuming by the times it has occurred according to what you have stated that it would have to be something not sealing properly, intake manifold would be where i'd check first, though i don't think you need to take that off to do injectors, at least i know the people that do my work don't have to, or at least i don't think they have to, anyway i'd start there and to me it seems as if it does it only at higher boost pressures