Rear projection tv overheating, making crackling sounds?

my tv is making a crackling noise when I turn on the tv (it takes about three minutes till it starts getting noticeable). I was able to get rid of the crackling by sticking a fan behind the intake for the fan inside the tv. I was thinking i just need to get a replacement fan but before i do that i want to make sure that it will fix it and if there is more stuff to buy.