Water pump or radiator

My 81 Camaro (305 4brl with 4-speed), is running hot to the point I can not turn on the AC. It gets worse on the highway, and better if I turn on the heat. I just had the radiator flush and filled at a quick lube place (they had this vac suck/push antifreeze unit). It does not over heat (becasue I will not let it), but gets around 240 when i finally put the heat on. Which do you think it is water pump, or radiator?? THANKS

Radiator for sure after 30 years. It is so gunked up it cannot possibly transfer heat anymore. Flushing won’t do it. For a couple hundred you can replace it with a heavy duty one. Doesn’t mean you won’t need a pump too at some point but usually that is from leakage and not from the fins disintegrating. Think about it, if you turn the heat on, you are adding cooling capacity to the system which says that you don’t have enough.

What’s wrong with changing both of them and the thermostat? Your car is so easy to work on that you can do only one and not worry.

Look at the radiator; if you see white or green on the bottom of it, change it. If you see the little fins missing between the tubes (5% to 10% missing) change it. Check it from the back of the radiator with the shroud pulled back, unless you can see problems without doing that.