Question Toshiba C660-173 Over heating issues

Jul 13, 2021
I have a toshiba C660-173, i know its an old machine and really should be retired but its still a good machine, I seem to be having a very odd issue with it over heating. On a level surface it seems to be fine, but as soon as you tilt the machine from the touchpad edge upso the pivit point are the hinges edge of laptop, the machine seems to get hotter and hotter according to the CPU and then will eventually switch off, the fan works fine and the venting is on the side and bottom of the laptop and not the hinge edge and blows out cold air. whenthe fan kicks in and i then place the machine back to a level surface its fine and continues to work without issue, tilt it again and get the same issue, the fan kicks in and will eventually switch off.
i've check all systems, clean the heatsink and made sure there is no dust in the fan. and clean and put new thermal paste on as well and still get the same issue.
Im at a bit of a lost as it seems to be doing the exact opposite to what you expect it to be do. Any advice or suggestions? The manual says there is a temperature sensor but i dont know where that is to make sure nothing is causing that to over heat.