Crazy hissing noise under boost!

[canada6.0]

I just got back from my mechanic who did an oil change and changed out the fan clutch on my 2008 F450.

The truck as an S&B intake, H&S mini maxx, 5" turbo back exhaust and an EGR delete. Its had these mods for 20k miles with no issues.

About 70miles into my way home I heard a really loud hissing noise from what first sounded like it came from under the drivers side of the dash. I pulled over and noticed that my check engine light had come on.
The truck had thrown a "turbo/supercharger performance" code. I can't remver the actual number.

I cleared the code and drove the truck home slowly.. still making a crazy hissing noise but not throwing the engine light back on.

I checked the turbo hoses and it didn't really seem like they were ripped, plus they are on the passenger side so it wouldn't seem like that would be the culprit. the truck would still put out a healthy amount of boost and I didn't really notice a loss in power. I wasn't pushing it hard after this happend so I can't really be sure about the power loss but it wasn't noticeable at normal highway speeds.

The truck is going into a local diesel shop in the AM (they are Duramax specialist so i'm a bit hesitant trusting them with my truck).
My mechanic is about 100 miles away and I have to leave for a race weekend day after tommorow so I don't have time to go back to him.

Any idea on what this could be so I can maybe steer the local shop in the right direction?

Thanks in advance!

[srjd]

I've heard of this before it's a cracked up pipe I believe.... Someone else will chime in but I think that's what it is

[04hdfatboy]

Ya i would also guess a leaking up pipe.

[canada6.0]

So we figured out it was a broken Back Pressure Sensor Pipe.

I never heard of that before but apparently is a common problem.

Thanks for the help guys!

[brewda]

I am also having the same issue. How was it replaced? Was it a cab off? Thanks in advance

[hammett88]

When mytranny locks under load it makes a hissing noise:. Sounds cool but is this the same thing? Hurting performance?

[canada6.0]

Originally Posted by brewda

I am also having the same issue. How was it replaced? Was it a cab off? Thanks in advance

I didn't do the fix, I dropped it off at a diesel shop by my shop and they had it fixed in an hour. Was a cheap fix $150ish with the diagnostic, part and fix.

Originally Posted by hammett88

When mytranny locks under load it makes a hissing noise:. Sounds cool but is this the same thing? Hurting performance?

I dont think that's the same issue. Mine was insane loud and definetly hurt performance. Basically lost all my low end grunt, my tweaked 6.4 was running like my old stock 6.0.