'04 3500 Cummins sounds like a coach's whistle under boost

[Rogan]

A buddy of mine has an 04 3500 6spd, 4wd, srw, 248k milesHe has a bhaf, 3pc exh. mani, 4" turbo back exhaust, and a predator programmer.the past few days, he's noticed a noise under boost. I haven't heard it, but he likened it to a coach's whistle..He initially thought his turbo (351cw) was failing, but I said no, as it's fine and makes tons of boost.I think it's a leak or something somewhere. While inspecting his truck last night, I noticed that the vband connection from turbo to downpipe is leaking. It's tight, so I think maybe a flange lip is trashed or something..could that sound be from there?He's also starting to push oil a little. Taking the trim off of the valve cover, the top of the cover is pretty oily. Possibly the filler cap and/or that thingamabob that bolts to the middle of the cover (some pcv/emissions thing?)Any assistance is appreciated.

[dorkweed]

Does the whistle vary under different engine loads and throttle positions??

[Rogan]

Does the whistle vary under different engine loads and throttle positions??

Unfortunately, that, i do not know. I didn't get a chance to test-drive it.. he said under lo-load, no-boost conditions, he doesn't hear it..

[mr.mindless]

Sounds like a boost leak to me. Tough to tell from under the hood with no load.

[flagmanruss]

I was going to guess boost leak but mr mindless beat me to it! First place to look is the boots... probably find one has blown or slipped.

[silverhocummins]

I would say boots on pipes too. I had this a few years ago on my 03 HO. I repositioned and re tightened and it was fixed.

I was going to guess boost leak but mr mindless beat me to it! First place to look is the boots... probably find one has blown or slipped.

[Wild and Free]

Check all the boots and clamps between the turbo and intake and then inspect the intake itself for a blown gasket and same with exhaust manifold although that usually sounds like a tick but not always. I would not think a clamp post turbo would result in a whistle sound if he has a free flowing exhaust, whistles come from a pressure source.

[diesel4life]

Also if hes got a boost gauge to check all the plumming for it. I was with my buddy one day when his line blew at the comp fitting under high boost conditions and it was a very high pitch noise coming out of such small dia. tubing

[Rogan]

He does NOT have a boost gauge OR an egt.. :banghead:I'll tell him to look for gasket failure.I did see a little soot at the exh. mani where the turbo bolts to it; it was about a 1" wide spot at the flange mating seam.The big leak I saw was definitely the v-band flange area.. Soot all over it and adjacent components..

[AH64ID]

Are you sure it's a 3-piece manifold? Those are 2nd gen style, which means it has custom piping and that could be the source of the leak. Have him check and see if his intercooler has plastic end caps.

[Rogan]

Yes, he installed that a year ago. Sent from my SPH-L710 using Tapatalk 2

[AH64ID]

Yes to the 3 piece or the plastic IC?

[Rogan]

Sorry, John. "Yes" on the 3pc exh. manifold.

I'll text him about his intercooler end-tanks..

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Aluminum

[AH64ID]

Since the 2nd gen setup took some manipulating of the intake pipes I would start there looking for a misplaced boot, etc. As for the exhaust leak, did the centering pin get put back in the hole when the exhaust was moved for the 2nd gen swap? Diesel exhaust leaks are generally silent, but at the exhaust pressures the stock turbo creates I would say a whistle is possible. I would also check the filter tubing, as that can make more whistle too.