Changed the thermostat in my 2002 B4 Legacy this morning.
Noticed bubbles coming from the overflow.
The car isn't over heating, coolant isn't boiling, A/C blowing hot air as it should, Thermostat definitely opening, Oil clear and clean.
Going to be replacing the radiator cap and bleeding the cooling system again with the front jacked up this time, did it on a hill the first time hoping it would have the same effect.
Any other ideas of what it might be or things to try before considering the possibility that the head gasket randomly started leaking straight after putting a new working thermostat in?