So with the general consensus being that the t-stat is either bad
or installed improperly, or the wrong one, did you actually remove
the t-stat (2 bolts ) to INSURE a free flow to the radiator?

Inquiring minds want to know.
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Comparing the hose size of the radiator hose versus the
(possibly clogged) bypass hose, The answer is looking
easier to figure out.

I also concur that it is better to replace a cheaper object
t-stat before a more costly object like a radiator.

So what have you found out?-Bob