Have you seen the exploded view of that style valve? The valve can be completely taken apart for cleaning. That's what I'd do. Then it's just a matter of spraying it out with brake clean and compressed air.

Look here...
https://board.moparts.org/ubbthreads/upload2/7489638-poportioningvalve.jpg

Last edited by burdar; 05/02/13 08:08 PM.