My 98 F-150 recently displayed TC 0455 (EVAP leak) had it checked out at the dealer, seems the top of the fuel neck had a chip in it. They wanted 385.00 to replace the fuel neck. I filled the chip in with JB weld and all is smooth and fits good just like Factory original. However before the repair and after I hear a whistling noise when I shut off the engine. I had TC cleared and still does it . What is the problem?

 

My guess is that your patch job works well enough while the vehicle is running, but once it is shut off the pressure in the tank and in the atmosphere are allowed to equal out because there is a small leak. When air gets pulled through the repaired area, it makes a whistling sound. I don't think that it is a big deal as long as the tank can build pressure while running. It is the same thing that happens when you open the gas cap at a gas station; the tank and atmophere equal out, but the pressure builds again once the vehicle is run.

 

the whistling noise could be coming from your crossover which controls fuel draw from one tank to the other,its usually an indication the crossover is going bad.