Another trick the ZU guys showed me, and this will determine if its the fan, pop the hovod, with the truck in park, rev the engine to about 2-3k rpms manually at the throttle body. If the fan isn't sucking a bunch of dirt out of the radiator, your fan isn't working, mine is like a hurricane under the hood when I do that and you can drop temp back to 170 in less than a minute.
Should i try this on a cold Modor or let it warm up a little bit also how do i know if it's sucking dirt from rad. Do I just open the cap and look for bubbles is that what you mean?