Dakota R/T owners
I had to use a pressure washer to unclog mine the last time.
Just so happens my PW wand is a perfect fit for the 5/8 heater hose.
Took nearly an hour going back and forth from the hose on one side to the other 2 minutes at a time before I got a clear and consistent stream !!!
I'd drive to Detroit and personally smack the fella who designed that system, if I thought I could find him. Worst part of the whole truck.