Stange noise upon throttle let off.

[Railroadguy]

Recently purchased an 06 6.0 with 35k miles. Neither carfax or oasis show anything other then routine maintenance. On a recent 250 mile drive truck got 18.6 mpg. (hand calc and dash readout agreed and im aware of the proper way to figure everything)

I noticed when heading home that when letting of the throttle i hear a slight chirping/whirring sort of noise. Truck seems to have plenty of power. Also I can smell exhaust smell when standing on the drivers side of the truck. Is it just wind moving it around or a leak somewhere?

I don't know what a healthy 6.0 is supposed to sound like when idling either since my last truck was a 7.3. I don't know anybody with a 6.0 to go listen to either.

There is some crust around the degas bottle underneath the cap but I have read on here that could have been from running the truck fairly hard or from the dealer spilling coolant topping off the bottle or a bad coolant cap.

Any ideas? I really don't want to have to stud and egr delete yet or replace a turbo. Could it just make the noise for whatever reason?

Also the truck was sold right at 4 years ago. Does the factory 5 year/50k warranty still apply to me even though im the second owner? Dealer said no warranty but if i understand correctly the powertrain warranty is different.

[rdodger]

had a similar problem and replaced the cap of degas bottle and noise went away not sure if it solved the prob but the noise stopped