I had the same problem in my 1993 Honda civic, and if your driving with
an orginal radiator, than I would strongly suggest replacing it. After
I did this there was no problems with the car overheating. Remember,
the radiator is over 12 years old and is made out of aluminum and will
slowly get smashed, damaged, melted and well you get the idea.
I bought a new one off this guy:
His prices are VERY reasonable compared to other ebayers, and he
doesn't charge rip off prices on shipping. Some of these people who
sell radiators ask like $50 but then another $70 for shipping, and
that's a rip off.
I paid about $40+30 for shipping, and that's a great deal. Just email
the guy if he doesn't have any listed, and make sure you buy a COPPER
radiator, so you won't have anymore problems.
I had my copper radiator since march, and its been working perfectly. I
had to drive around like you do, with the heat on and I live in Atlanta
and it's daily 90+ and very humit. I know how much of a pain in the
arse it is.