The pc keeps shut down due to thermal heat

"If your PC shuts down ""due to heat"", I suppose it means it starts when cold and shuts down a short time after.

You say you cleaned the heatsink of the processor. Maybe you moved slightly the heatsink and the thermal contact between processor and heatsink is not good enough any more. Recent processors are protected against overheating, and shut down when they ""feel"" hot.

Maybe you just have to put new thermal paste or thermal sheet between processor and heatsink. The thermal link generally works well only at first application."

you need to apply new thermal compunf between the cpu and the heatsink