I have a 96 Sentra with a 1.6 liter engine with 120k miles.
Recently, I have had an overheating problem.   It occurred on a trip
to Florida (from Texas).   I handled it on the trip by turning on the
interior heater.   Fortunately, it was pretty cool outside and the
heat on the inside was beneficial.

Thinking the problem was the radiator, I brought it to a shop
yesterday.   The tech there did some flow tests and indicated that he
didn't think that the radiator would have caused the problem I
experienced.   I also checked the thermostat by placing it in some
boiling water to see if it functioned correctly..... it did.   After
reinstalling the radiator and the thermostat, I ran the car today in
the garage to see if the overheating continued.   Here is what I
found:

1.  the fluid was boiling in my overflow container, while the temp
gauge read in the middle range.

2. the lower hose from the engine to the radiator was cool to the
touch after running the engine 10 minutes in the garage.  The upper
hose was hot.

I would appreciate some ideas on what may be the problem and how I may
diagnose them.

Al Kondo