More likely the heatsink coolant has leaked out so the heat is not transferring to the fin area for the fans to exhaust out.
Heat issues can be hard to nail down. I find a thermal camera can be helpful.
Also be careful re-applying the thermal paste! I often encounter people over doing it creating a big mess and a more expensive repair needlessly. It only takes a very small amount of TIM for the task! To help you see how little is needed take a small square the size of the chip of one layer of tissue paper. Now wet your fingers and roll it into a tight ball. Even this it too large!