I have 1974 firebird, I know it's not a thirdgen but it's pretty much the same. Anyway, it has been over heating lately, i'll be driving and it just heats all the way up, the water pump was just replaced about two months ago. So I replaced the thermostat today and it still heated all the way up, I was monitoring it the whole time and it went up to just under 210 and the thermostat still wasn't opening (I had the radiator cap off and I didn't see the water flowing and thought he upper radiator hose was hot it didn't feel as if water was flowing through it). Now this leads me to two conclusions, either the thermostat needs a little more time to open, i don't see why it wasn 't opening because it's a 195 degree thermostat, or the water pump is bad, but even if the pump's bad shouldn't there still be a bit of water flowing if the thermostat opens?

Any suggestions? thanks in advance guys

 

Don't know for sure,but i think those pontiacs are
supposed to have a sheet metal plate behind the
water pump impeller to direct the flow properly-if
plate is missing or has rusted away,the impeller
just thrashes the water and little actuall pumping
occurs.

 

possibly a faulty thermostat.
ive gotten faulty ones before, so i just went and got a hi-flow one from summit.
or take out the thermostat and see if the problem still happens.
just a process of elimination