97 1.6l ce Coolant problems

97 corolla ce with the 1.6L bought car started having coolant issues replaced thermostat then it overheated did head gasket on car then a couple weeks later radiator blew open driving down road from to much pressure? Previous owner dumped stop leak in it so replaced radiator been getting bubbling through upper return hose and pressure bubbling into overflow tank since before I did the head gasket new radiator cap and thermostat still have bubbling issue heat only works in car at high rpms could it be bad water pump ? Car temp stays at half ( normal) area throughout drive but loses coolant due to bubbling in overflow... any ideas on why its bubbling lower radiator hose to thermo is barely warm to touch while upper is scalding hot and can feel bubbling system was pressure tested and exhaust in coolant tested by mechanic both were normal
Are you getting heat? I dumped a bunch of radiator stop leak into my system once and it totally plugged my heater core. Just wondered if anyone had used any stop leak.