will the motor over heat if the thermostat is put in backwards? if not then I have a question, my rx7 keeps overheating and there are no leaks,and the heater core is good. what is going on? anything would help

 

does the thermostat go with the cone point pointing down or pointing upward? I pulled it out without paying attention.

 

spring side down

 

There should be a small spring loaded discc, standing off from the main thermostat valve disc.
It closes a bypass port inside the pump housing.

 

Upside down is bad & will force the engine to overheat.
If you are not loosing or displacing any coolant - that's good.
Here are some possibilities.
The fan clutch is getting weak.
Trash (leaves) blocking the narrow gap between the oil cooler & the Rad.
Missing fan shroud, or lower or upper plastic shields in front of the Rad.

In my case, it's a bad internal coolant seal..