Ok my quest is prob easy for a real mech.But im not so i have to ask.I got a 87 with a 3.8 and likes to run hot.Ive changed the thermo to a 160 cause a buddy said it would be ok to run a 160.And the heater core is bypassed for now and i even flushed the radiator out.I havent let it get in the red or it hasnt got there yet but when i park it and pop the hood ya can hear and see it bubble in the overflow tank.I just tinker but not a real mech so thats why i came here to ask.
Time for head gaskets.
160 thermo is bad for your car,will run in open loop all the time and will be pig rich,no reason you should need to run that cold of a stat,either your water pump impeller came off(doubtfull) or you need head gaskets.
Definetley shounds like gaskets though.