I had a similar issue with my YLOD ps3 which I was fixing every week or two. I saw this tip on a YouTube video and my PS3's been working for over a month now.
When you tighten down the heatsink plates, if you do not screw them down evenly, the heatsinks will not sit flush on the chips which may be the reason your fans are blowing hard.
What you want to try is turn the screws in about 3-4 turns each switching back and forth until they are tight instead of tightening down 1 screw at at time. This will help sit the heatsink flatter on the chips, hopefully, dissipating more heat.