A friend of mine has a 2000 7.3 all stock with 80k on it.. When it is cold out it starts up fine but makes the sound of an air leak and almost a whistle.. Very loud.. Been to the dealer they have no idea what the problem is..
After 15 min the sound goes away and it runs all normal sounding again.. I did not realize a drop in throttle response but i dont drive the vehicle alot.. Does anyone have any ideas?

 

Its the exhaust bp valve. It closes to heat the engine up faster. Is the noise coming from the exhaust? If it is, then that is what it is. My excursion with a straight pipe sounds like a fricken rocket blowing up!

 

yes it is.. Why thank you for the fast response

 

I think you will notice that has soon has you hit the brake of throttle it will go away. That is what the bp valve dose. promotes faster warm ups! When I put the 4" exhause system on my 02 it really made A hissing noise! LOL

 

Wow, the dealer couldn't figure that out?

That's pretty sad, man.

 

LOL... Classic Dealer call...