I'm having a heck of a time with mine on my 470's. I've tried remounting them, even with fresh thermal paste but it seems like it's not making proper contact.

Everytime I remount it and power up the loop I get about 4 minutes before the gpu fan ramps up to 100%. I kill it in fear that I'm overheating the card(s). I'm gonna start my own thread, if anyone wants to help.