How to access laptop internal fan?

I have an (old) HP Pavillion dv8320us entertainment notebook PC. I believe it is having serious heat issues. It keeps shutting off unexpectedly after only several minutes. I purchased a cooling pad and even that doesn't work. The only way I can get it to stay on is to actually set it ontop of a face up electric fan lol. I thought maybe opening it up and cleaning the fan would work (I've tried canned air already), but I can seem to find how to get at it. There's only a panel for the battery and a screw panel for the motherboard. Does anyone have any advice, this current setup is NOT cutting it. Thanks.