well, the whole ungodly story:
Car always ran somewhat on the hot side after I got it (one of those
"program cars"; last year's model, but never registered, with 1K miles
on the clock, not a dealer demo, supposedly just used to run people
around the Honda campus up near the airport here) I assumed it was
normal, given that silly teeny radiator. Over the years it got hotter
to the point I was driving around on hot days in the summer with the
heater on. Finally in the infamous summer of 98 it was so bad I
replaced the radiator before the motor ungasked. Plain jane
aftermarket $200 replacement radiator, indistinguishable from the
original. Temp gauge now never went above not quite 9 oclock. boy did
I feel silly. Everybody tells me now how efficient honda cooling
system is even with teeny radiator. But now, in winter it doesn't rise
above 8 oclock. Takes a couple of miles to get warmed up, summer or
winter. So i swap the thermostat for one of the hanging on a card on a
rack ones in the car parts store. No different. i figure, that's what
I get for getting a car parts part, so I swap it for a Honda
thermostat. No different. ?? Must be that efficient Honda cooling
system.
Then, the head gasket expires from the previous overheating anyway, so
instead of fixing it in goes the B16. It's got the same "highly
efficient" cooling as the D16 did. That was a few years ago, this
winter the cooling seems way too efficient on the highway; pull off
into the city, and it goes up to normal heat, so it seems like Too
Much Cooling Through the Radiator. Which, with a stock radiator, has
to be the thermostat? But as I said, I don't see any flow in the
radiator with the engine cold. And four different thermostats in two
different engines all with the same problem????

Nope, reservoir's full to the max; opening the cap on the radiator
it's almost up to the bottom of the neck, which is what I always see
on other cars.