i have a 2005 f-150 fx4 and its making a squeeling noise under the passenger dashboard it only happens when i accelerate my buddy told me that it might be the heater core that it might be getting plugged up so i flushed it with drano and water and it still making the noise any suggestions would be appreciated

 

Is it a whistling noise that changes with rpm?

 

no,it happens when i take off or if i accelerate fast

 

I've heard the belt slips sometimes under a big load (taking off can be considered this) and you hear it squealing from under the hood. why its coming from only the passenger side of the truck, i dno.