Some of you may know I have added a second FC3 to my list. I was doing the e-fan mod and noticed the bright look of aluminum on the radiator fins. the frame is plastic which sux, but did these cars come with an aluminum radiator?
If so why is my car still over heating with the a/c on?
I have a 16 pound rad cap and tommorow I will have a gutted thermostat.
I am running 75% water and 25% coolant because water has better heat transfer properties than anti-freeze?
I am also running synthetic oil, which lowered the operating temp of my other FC, but not this one.

 

The radiator core is aluminium but the end tanks are plastic.
Go get a thermostat from Mazda (nowhere else). A gutted one won't cool better, it'll just take longer to warm up.
Your overheating problem could be a number of things. Since it's only with the A/C on, you must be right on the limit all the time, and the A/C just a bit too much. Does it overheat when idling with the A/C on?
Have you flushed the cooling system (radiator and block)? Are the radiator and condensor fins clear of crap? Is the undertray still there?

 

Are you running premix as well??

I know it's a topic of heated debate, but I'm gonna stick with mazda on this one.... don't run synthetic unless u are running premix AND have your oil injection disabled...

 

New Mazda thermostat, definately...

New radiator, probably...

New water pump, possibly...

Look at the water pump for external wetness. There is a weep hole that will leak coolant when the seal in the pump goes bad.

Flush the radiator, and try Redline Water Wetter. If its still too hot, the radiator is probably clogged or restricted severely.