My Sapphire 7970 has been a PAIN in the ass ever since I got it.  I switched over to LTC a few weks ago, and it took me forever to get the hash rate up to 725 kh/s.  Once I finally got that sorted out, my temps started to become a problem.  When I first started mining ltc, my temps were around 75-80c. The temp slowly kept rising till they were in the 85-87c range!  I had the side of my pc open and a box fan blowing right on the card, and it helped a little at first, but then the temps were back at the 85c range.  This is in an air conditioned room. 

I tried cleaning the card, maxing out fans etc, nothing helped, and it was driving me nuts.  The pc kept restarting itself from high temps.  I finally ordered some thermal paste and replaced what came with the factory.  It was super easy, 4 screws and a twist and it was open.  The factory paste was thick and had spilled all over the transistors surrounding the chip.  I cleaned everything the besi I could, used a toothbrush to get the paste off the transistors, and added the new paste.

I am now running at max load, an hour later, I am at 735 kh/s and gpu-z says my core temp is at 58c!  my VRM temps are at 78-80c!

I hope this helps any one else struggling with rising temps this summer.