Hey I have a 1984 Mazda RX7 FB GS and yesterday I was driving it and got home and parked and it began to bubble out of the Overfill reservoir and hasnt done it while I drive it only at idle could it be water seals or a bad fan clutch?

 

How old is the fluid, radiator, pump etc? Start with the simple stuff, does your temp gauge work? If so is it hot when driving? Do you have a temp gun to check the temps, upper, lower hoses etc. is one hose hot and the other not?

Sounds like the cooling system may be clogged, i.e. broken thermostat, clogged radiator or the impeller may be broken.

We need more information, which engine, mods etc.

 

Could be a bad cap that can't hold the pressure. What did the temp gauge in the car read?