No check engine lights, no smoke..i just did a dyno on it and everything came out just perfect, they took it apart too they said, nothing!

Its a very good truck they said, Freightliner in Charlotte that is.

I was told while in Toledo Freightliner that sometimes the ,,veins'' inside the turbo itself change the tune and start to sing on their own...

No power loss at all..

Could be a very slight leak at a clamped connection between the turbo and the intake manifold.

This would include all the connections at the turbo, CAC, and intake manifold.

Check the CAC for cracks near the header especially on the hot (turbo) side.

Could be an intake manifold gasket.

Also check the air line that feeds the air compressor with turbocharged air.

I've seen instances where a miniscule leak in any of those places can cause a "whistle" or "whining" sound which rises and falls along with the turbo whine. Not enough of a leak to affect the boost pressure or engine output, but enough to make noise.

Possible guess, Series 60 Detroit - FLD or Columbia!

They all do it! The '06 I drive sounds like a jet fighter at times. Something to do with the Turbo design, wastegate and the emission stuff! Can be quite annoying when trying to sleep.

Sound asleep, and it winds up for take-off! Ugghhhh! :sad:

Yeah, its 07 Columbia and everyone has told me that....

Splitshifter, thank you for your response, ill look into it myself.

Thanx guys.

Whistling turbos and long hoods are cool...until bedtime and fueltime.

Just put a Variable Vane turbo on my Cat. If you want noise that SOB will give it ti ya. Riding along it is fine but start wanting real power and you have to wind the windows up or put in ear plugs :sad: Good for running off deer though