right now im on my second rad because i developed a leak in the lower corner so i chnaged it out for a standard rad and added a tranny cooler. 3 weeks later im gettin a leak in the same spot on this rad and i really dont want to pay 350 for a new rad when theres a different problem causing all this. I went to add some rad stop leak and it instructs to remove the rad cap and let it run to normal temp then blast the hot air to ciculate it and add the stuff but when i removed the rad cap and ran it all that happened is the coolant gradually overflows out of the rad and doesnt seem to be circulating. now the reason this is confusing is because the car doesnt overheat and never goes over normal operating temp, i get extremely good heat and the cooling fan is working. I noticed that while having the rad cap off that there was no more leak in my rad so it possible than my thermostat needs to be replaced or could this be the water pump or something else??

 

I'd think since you're not overheating, it wouldn't be thermostat or water pump.
I'd be more concerned with where exactly that leak is and why after 3 weeks you have the same leak from a different radiator. That's pretty odd...
I understand its a good idea to replace the thermostat after using any kind of stop leak, as it could clog it.
Reason for no leak when cap is off: pressure. Without cap on, pressure doesn't build up, so it doesn't force that spot to leak. Ran into that problem when trying to find my recent leak. It poured out when engine was hot. Later, with cool engine, i added water, no leak. started car, pressure built up quick and i found the leak.