Thermostat replace and the water getting to about 200 deg and moving fine, but just fairly warm inside the truck.

This is driving me nuts. Read the book so many time my eyes crossed trying to find anything to point me in the right direction.

Anything ??

 

What temperature thermostat did you put in?

If the water is flowing well, then a reversed thermostat is out of the question.

Check the water temp at the heater core. Both the inlet and the outlet should have about the same temp. if one is way colder then the other, I would suggest a clogged heater core. You can either flush it out of replace it.

If the heater core checks out good then I would check the heater control to make sure it is working properly.

Start with that and we'll take it from there.

 

The heater core is probably clogged. Just disconnect the lines and flush out with a garden hose. Also stock thermostat is 195. So if it is getting to 200 your overheating.