I have to keep topping off my coolant about once a week and after a hard drive I see a puddle of coolant, leaking from the overflow tube. It backs up into the coolant reservoir but won't go back into the radiator or the lines. WTF? The temp never goes above normal. Its frustrating because the coolant is leaking out enough to make the buzzer go off, alot.
Any ideas?

 

check your radiator cap or your neck cap, It should have 2 working valves, one for sucking coolant into system and one for relieving colant into reservoir tank, it seem like the sucking valve doesn't work, just replace the whole thing.

5 bux at junkyard

 

happened to me. I had a blown coolant jacket. Start saving for a rebuild. And check for bubbles in your coolant (reservoir and rad) when your car is running.

 

The cap on the radiator controls the coolant flowing to and from the overflow bottle. If its not getting sucked back in you need to replace it. Don't use second-hand radiator caps, get a new from Mazda (nowhere else).
The cap on the filler neck is not a pressure relief cap, its just a plain cap. Don't put a pressure relief cap there or it'll probably leak under pressure. Unless it's leaking now, leave it.

 

maybe a heater hose needs replacing?