try installing a fan control application to see if it will help.
http://mac.softpedia.com/get/Utilities/Extended-MacBook-MacBook-Pro-Fan-Control.shtml
if not you fan could be inoperable and would need to be repaired. If there is an apple store close to you i would stop in for an opinion even if it is out of warranty. They may be able to diagnose the issue and you can then deiced how to address the problem. I would suggest self install for a fan but you will need to set 2-3 hours of time aside to do that.
-Varsity