How to find the cause of a YLOD?

@shawly since your PS3 seems to function with proper ventilation you do want to latch on to that. It could still be the processor just now you have better cooling. Do the usual by cleaning the vents, replace the fan and replace the thermal paste. Remember that there can be multiple causes for the YLOD:

Dead/Disconnected BluRay Drive

Cold-Joint between the CPU/RSX/EE(If your console has one)

Failing Power Supply

Overheating

Corrupted NAND Flash, and multiple others.

If that does not resolve the issue you know that you most likely have a processor error. Not sure about which reball kit you have. A proper reball needs the right temps and times to properly function so make sure hat you have the right profile for your processor as well as the right stencils for the solder balls etc. Here is the concern with all of this. The proper fix for this would most likely be a professional reball with a new IC (unlikely you can find one. The real reason for this is the design of the IC. It is a flip Chip design which has shown multiple failures for the PS3 as well as Xbox360 (as well as computers alike) which uses the same design for their IC. Here is a very "quick and dirty" explanation of what causes most of the YLOD/RROD. It is not always a failure of the solder balls which connect the Flip Chip BGA package to the motherboard. It does happen and you can see why on here More commonly however is that the failure is due to the chip design itself.

As you can see the "bumps" are what actually connects the die to the substrate to make the chip complete. If these bumps fail, the die does no longer make contact with the substrate and thus no contact with the circuit board. The chip has failed.

So what happens is that the chip heats up (due to poor design of the ventilation and heatsinks of the console. Does not matter if it is a PS3, a XBox or some of the Mac laptop's) and the bumps that connect the chip to the substrate lose contact and your chip (in this case processor) fails. The heating of the chip or a reflow actually reshapes (most of the time) the bumps to the point of making contact again. That is the reason why some reflows just do not work. The connection between the IC and the substrate has absolutely failed. In those cases you will need a new processor. Not the most scientific explanation but I hope it makes sense to you.