2002 P.T. Cruiser Overheating Problems?

After just now re-reading the FSM, I think you are 100% correct.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Same on 2nd gen. LH. As Joe has pointed out in another post replying to you, the 2nd gen. thermostat is down low on the side of the 2nd gen. LH engines. This may surprise you, but the thermostat is on the inlet side of the engine in the 2nd gen (at that engine end of the lower rad. hose). So the housing that is traditionally where the thermostat is just an empty housing (except that on the 2.7, it also has the bleeder valve on it). This makes the replacement of the t-stat on those engines (2.7L, and 3.2/3.5L) a bear to replace the thermostat on. Also, many people don't realize that the thermostat isn't in the traditional location. The FSM even mistakenly refers to that housing as the thermostat housing in a few places (boilerplate copied over from other FSM's and not caught). In case you're wondering what the proper name is for it since the thermostat isn't in it? Engine coolant outlet housing. :)

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

I knew that was true on the 2.7, but wasn't sure about the 3.2/3.5/4.0 family.

I gather that its not actually a reverse-flow system like the GM Gen-III engines, so I assume that the thermostat bypass flow somehow is routed in such a way that it allows the thermostat to sense the outlet temp while regulating the inlet flow. Seems strange- what's the claimed advantage?

You are correct.