I've used the search and read everything and am still at a loss. I bought my FC a year ago for really cheap because it was overheating. I let it sit for about a year without really messing with it as i was pretty busy. I knew there was a problem with the cooling system as when i opened the cap at purchase the only thing in there was rusty water. I drained the system and filled back up with a 70/30 coolant water mix. The problem got better and the car would run high but would overheat on the freeway at speed but would not over heat if started and left to idle. So i noticed later that only one side of the radiator would get hot, the left side of it would be to hot to touch while the other side was almost cold. So i put a new radiator in and new coolant again with about the same coolant water mix. I also removed the thermostat and replaced the radiator cap. Now the car idles fine and is fine on the freeway but the operating temp is high and it will overheat in traffic or normal street driving. I checked the fan clutch and it seems ok, two mechanics said that the clutch eas fine also. THe water pump doesnt make any noises nor does it leak so i dont think its the culprit. I've bled the coolant system so i doubt its air bubbles, also when i bleed it and fill it all the way up with fluid once it begins to overheat half of it blows out into the overflow tank. Anyone know whats could be wrong. By the way its a NA FC not a TII.

Statik

 

Replace the pump and put a thermostat back in there NOW and only a MAZDA OEM thermo. Check your belts and your hoses.

 

If you had rusty water in the radiator, it probably had no antifreeze in the system. Among other things antifreeze is meant to be a rust inhibitor. I've seen pumps that have run in un-inhibited water where the impeller is completely gone.

Rob

 

Any white smoke on startup?

 

Have you tried to flush water through the water jackets on the engine thay may be clogged and that could cause the engine not to cool properly.