Re: eVGA Geforce FX 5900 Ultra running VERY hot
Tightening sometimes helps but if contact has been broken it may not be a solution. Removing the sink and the thermal material and re-applying is the only way to establish a good thermal contact.
About RPMs, your fan has no RPM sensor so the simplist way is to just observe the fan and see if it is turning at a constant speed and not fluctuating or slowing down. If the bearings are going it will be making an odd noise. More than likely this is not the problem. The problem is either the thermal contact or the less wanted reason...the card is dying.
After replacing the thermal compound and temps drop some but not significantly you could do a temporary test and place a high output fan aimed directly on the card and see if temps drop. If temps drop you just need better cooling for the gpu and memory.