2005 Volvo S60 Reservoir boiling Temp Ok

[macten100]

Vehicle runs great until I start hearing noise from the reservoir. Then it seems as if it wants to pull back, once in a while. The temp never goes past the middle mark. Had the thermostat changed, but the hose still gets pretty hot. Has anyone had this problem. Water in the reservoir is about half full and never over flow. But you can hear the bubbling noise .