I'd say test the flow how you described...
If the t-stat is good then I'd say something is clogging the flow.
Take the t-stat out and put it in some water on the stove...see if it opens and closes.
I think you're on the right track...
Good luck!
------------------
Phil M. - Kent, WA
95 XJ Sport w/Stuff
"Who cares about a list of crap, can you drive it?"
If the t-stat is good then I'd say something is clogging the flow.
Take the t-stat out and put it in some water on the stove...see if it opens and closes.

I think you're on the right track...
Good luck!
------------------
Phil M. - Kent, WA
95 XJ Sport w/Stuff
"Who cares about a list of crap, can you drive it?"