YLOD Repair worked and quickly went back yellow

dellihuemario,first you will have to remember that there are a few things that can cause the YLOD. A few of them are:

A dead or disconnected HDD

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

A dead power supply

Overheating

Corrupted NAND Flash

Even reflows are only limited. YLOD (as well as RROD on a Xbox) are most commonly caused by the design of the processor, not necessarily by bad or cracked solder joints. You most likely have issues with your GPU processor. It is a flip chip design and the issue could be the solder bumps between the IC and the substrate. A reflow might fix it for a while. Even reflows are only limited. YLOD (as well as RROD on a Xbox) are caused by the design of the processor, not necessarily by bad or cracked solder joints. The only repair that would fix it permanently is a new BGA. Try this repair again and you may have to change the approach a bit by adjusting the heat. It is a hit and miss situation and most first time failure with this is caused by not applying to much heat, whereas to much will totally remove the IC's. Yes, replace the thermal paste again, do not add to it.