Issue with 2 Rrod fix on xbox 360?

I recently was trying to repair an xbox and before i started on it i turned it on and it was 3 rrod's, then i tried it later and it was 2, so i did the x-clamp fix and put thermal paste on to the cpu and gpu (for 3 rrod's), i plugged (without fan in) in the xbox and it turned on, the 2 rrod's came back and the xbox turned off again with the lights still flashing 2 rrod