that is a pretty old chip, if the thermal paste was never reapplied since around when that chip came out, it is probably due for new paste. also there could be a lot of dust in the heat sink. ( it could even be loose, but that is unlikely)
first things first see if it is dusty, then take it off clean it, and put fresh paste on arctic silver 5 is great stuff. then re mount it. just beware, some intel stock heat sinks do not like to come off or go back on easily.