I've been going through the cooling boards for a day or two, so I'm fairly sure of the things I need to do, but I'm still somewhat confused....

My car has been severely overheating, to the point of boiling. It happens during stop-and-go city driving only, so I’m fairly sure it’s not an air dam issue.
I am at the point where I’m ready to replace EVERYTHING! Trouble is I don’t know all of the components that make up our cooling system. However, below is my list of things I’ll be checking/changing:

1. Checking radiator for leaks, cracks, clogs, leaves, etc… The radiator is about 4 years old.
2. Check hoses for cracks, leaks, etc. Make sure they are not collapsing when hot. Bought a new lower radiator hose today, but it doesn’t have the spring inside…
3. Check thermostat; make sure it is opening, not leaking. Bought a new one in case the old one is crap.
4. Change coolant/water ratio. It hardly ever goes below 45*F or so degrees here, so freezing isn’t an issue. It DOES go over 100*F, so cooling is all that is needed, freezing is something I can only dream of. Therefore, 25% or less coolant, 1-2 bottle(s) of water wetter and the rest distilled water
5. Make sure water pump is working, not leaking. If not, get new one; possibly a Steward high volume mechanical pump.
6. Replaced the radiator cap. 15 psi Prestone vented radiator cap.
7. Something is severely wrong with my engine, and I can justify getting a new 383 ci engine?



What else should I think of?

 

0.) Check fluid level.

1.) Make sure the clutch fan (if you have one still) is still operating correctly. At higher speeds, air flow alone over the radiator can be sufficient enough for heat transfer to occur. At slower speeds, the fan is the staple for air flow.

2.) Pressure test the cooling system: if you do not have a pressure tester, autozone has one on the loan-a-tool program. Just pump it up to about 7 or 8 psi and watch for the needle to drop. (If the car is fine at higher speeds, don't expect too see a drop, but its pretty much a free check, so it doesn't hurt)/

3.) If the pressure is constant, replace/test the thermostat. Test the old one with the pan of boiling water. If it does NOT open as the water boils, or opens very little, you found your problem. If it functions fully, keep looking. If you have never tested a thermostat before this way, might want to check your new one as well, just to see how fast it opens, etc (for grounds of comparison).

4.) Might be benificial to flush the entire cooling system. Gunk has strange ways of building up and blocking critical ports. If you never have freezing conditions, distilled water and a wetter would be fine.