Whistling noise around 1000 rpm

[van1196]

I have an 08 GMC Sierra 2500 HD with about 85,000 miles on it. Noticed a weird whistling noise the other day while pulling out of a parking lot. I only hear the noise around 1000 rpms. I thought it might be the water pump, idler pully, or tensioner so I took the serpentine belt off to see if the noise would go away and confirm my suspicion. I started the truck and got the rpms up around 1000 and the noise is still there. Not sure what else it could be. Any help or advice would be greatly appreciated. Thanks

 

[2004LB7]

Boost leak maybe?

 

[dmaxfireman]

How about some details on the truck, do you have a boost gauge? Any recent work done on the truck? Any modifications to the truck?

 

[zakkb787]

Also, just so you know, water pump is crank driven not pulley driven

 

[ChrisPerry]

Does it happen rev'd in neutral or only when under load? If under load, stand on the brake and boost it up a little while someone locates sound. Just don't run anyone over.

 

[JoshH]

Drive pressure leaks at the up pipes can cause a strange kind of hollow sounding whistling noise. I compare it to holding a blade of grass between your thumbs and making a whistle like that.

 

[van1196]

How about some details on the truck, do you have a boost gauge? Any recent work done on the truck? Any modifications to the truck?

Banks Six Gun with PowerPDA. Doesn’t work right now because it needs a new EGT probe. The PDA reads high EGT temps and the tuner defaults back to stock. I just need to order a new EGT probe from Banks one of these days.

 

[van1196]

Does it happen rev'd in neutral or only when under load? If under load, stand on the brake and boost it up a little while someone locates sound. Just don't run anyone over.

It happens around 1000 rpms either in park or in drive. It goes away above 1200 or more rpms.

 

[van1196]

Also, just so you know, water pump is crank driven not pulley driven

Thanks. Good to know. I’m used to gassers. Diesels are a whole new world to me.

 

[2004LB7]

Maybe do a video for us. Not being there to hear it is going to make internet diagnostic hard

 

[J_Stone06]

It happens around 1000 rpms either in park or in drive. It goes away above 1200 or more rpms.

Sounds like a boost leak. If it's a stock y bridge/intake horn setup those are known problems being a two piece design. It could also be the bellows on up pipe which can crack. I say this because I had a similar issue a few years back. Mine was the y bridge/intake horn. I'd recommend doing a boost leak test for starters. If you hear your turbo normally it can drown out some or all of the whistling you hear at higher RPMs, as was in my experience. There are write ups or YouTube videos on how to fabricate a boost leak tester if you decide to go that route.

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