I had bubbling in the reservoir. I changed the thermostat and a heat sensor. But it kept doing it. I had air int je system. I had to empty the radiator from the bottom. I bought a new reservoir . Before putting new coolant in. There is a white screw / plug on the radiator topright passenger side unscrew that add coolant slowly. When coolant comes out the hole. Plug up hole and turn on car keep an eye on the reservoir add slowly until filled between min and max.
Do a block test to check for combustion gases in the coolant. Could have a bad head gasket or cracked head. Also test with your scantool the cooling fan assembly. The fan sounds like it runs on high, but may not run on low speed. If low speed does not work and the relay is good, the cooling fan assembly may need to be replaced.
