is this the thermostat?

I do not know the unit, But, Gurgling, is not a problem in itself, You have gas and liquid in the system. But. All the time. might point to something else. As fridge is ok, and compressor running, Freezer thermostat is a possibility. Thermostat in sealed unit above door, probably not, general, thermostats needs to be accesible in case of fault. so will not be sealed. Probably behind panel in back of unit, look for some pull off panels etc, Might only be screw covers etc, size of a screw head. But will not be sealed.

SD
October 2011