i have a 87 t2 its my 4th rx7 i have had it for about 5 weeks and last Friday i had my very annoying low coolant buzzer start yelling at me so i added some to the system and 20 min later it dose it again my last rx7 did this after i over heated it and i knew it was a seal because it would burn coolant every morning this car has not been over heated and dose not burn it it just keeps overflowing and i keep adding the system is not leaking into the housing and and the the systems pressure is normal i don't want to tell my self that its a coolant seal i just haven't seen a blown coolant seal that doesn't leak into the housing

 

You might have a pinhole leak in one of your coolant hoses.

 

but would that couse it to fill my over flow tank

 

Could be air in the system, follow the FSM and bleed it properly.

 

A pinhole leak in the hose from the pressure cap to the overflow bottle will allow coolant to be pushed in the bottle but not sucked back into the engine. In addition, a bad pressure cap will cause coolant to boil in the system and push itself into the overflow.

 

I know this has already been statedm, but to reiterate....bleed your system!
As well as the other points everyone else has stated.

Take your filler neck cap off and start the engine, to make sure it's not blowing out. Indicating a blown coolant seal.

 

If it couldn't, I wouldn't have posted what I did