Hissing From Tailpipe On Long Idle

[AcadianArts]

Like the subject says, after idling for a time, warm engine, I have twice now heard a hissing sound (vs the normal deep throated locomotive-like sound) at the tailpipe. Any ideas what that might be?

[Racer9]

That would be the dreaded idle snakeThe longer you idle, the madder he gets

[AcadianArts]

Now that we've heard from the peanut gallery (seemingly a necessity..) perhaps we can get some technically-oriented comment or idea of what could be producing such a noise.

Thx.

[driveitlikeyoustoleit]

Does it kind of sound like your exhaust brake kind of hissing?

[AcadianArts]

No, I believe that (e-brake) is a gentle sound from the engine compartment. This is a sound of air discharge over the sound of the exhaust, loudest at the tailpipe and it stops with a bit of a touch on the accelerator as far as I can tell.

Next time it happens I'm going to take a video of it so I can post the sound.

[illflem]

How long of an idle are you talking about?
Extended idling is bad for these engines, Cummins says no more than 5 minutes.
If cylinder temps are too low unburnt fuel washes the lubricating oil off your cylinder walls, compression escapes past the rings.
Maybe that's what you're hearing, along with the destruction of your engine.

[howdy]

if it is a cold start then it is the truck trying to heat itself up

[AcadianArts]

Thanks for all the ideas so far. As promised, I have two videos, one with the way it usually sounds, it's longer because I like the sound. The other displays the non-standard sound. Hope it helps to get some idea of what it is and possibly how to fix or avoid it.

Good:

Not-So-Good:

[cumminshakesit]

hmmmmm, my dads 91 did that ALL THE TIME, it turned out to be a pin-hole in the turbo housing... that is strange it doesn't do it all the time... good luck.

[torquey]

the peanut gallery lol.....we don't get paid to give advice on here..it is not a service