Depends what is causing the heat. If it's coming from the hard disk more RAM will definitely help. Otherwise probably not.
It also depends on where you keep your laptop. Is it raised? Do you use it on your "lap".
That's not really good...
I upgraded my macbook's RAM from 2GB to 4 GB yday. After installing the RAM, I find that my macbooks heats up to 89 degrees. Is it because of the additional RAM?
90f is like nothing! mine runs at 120-135f