Boots & hangs - replaced thermal grease - no joy

I have an a1055. It boots and hangs after a minute or so when cold. When warm, it will boot to a blue screen after the gear and hang.

I saw recommendations of replacing the thermal grease. I did that but it did not improve the problem. I really think this is a heat issue as I was able to pursued it to re-format and install the os by having it sit on a cold pack.

I have a couple of question:

1- when I got inside, I found that it used the heatsink material, like foam, instead of thermal paste. Would using thermal paste provide enough contact to dissipate the heat? Do I need to find more of the heatsink material instead?

2- any ideas what might still be wrong? I am not certain the fan is working. I think I hear it when it boots, but it seems to shut down after initial post . . . I think. It's hard to tell for certain when everything is coming on at power up.