If you got nothing to lose....
Open you PS3, clean the surface on the CPU and the GPU with this or isopropyl rubbing alcohol : http://cgi.ebay.co.uk/ARCTICLEAN-THERMAL-CPU-PASTE-CLEANER-REMOVER-PURIFIER_W0QQitemZ200328366388QQihZ010QQcategoryZ46322QQcmdZViewItem
Then put a new thermal paste on the CPU and GPU : http://cgi.ebay.co.uk/ARCTIC-SILVER-5-AS5-THERMAL-CPU-PASTE-COMPOUND-3-5G_W0QQitemZ200328366470QQcmdZViewItemQQptZComputing_ComputerComponents_Fans_Heatsinks_SR?hash=item200328366470&_trksid=p3286.c0.m14&_trkparms=72%3A1690|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50