Sounds like a incorrect temperature reading to me, because if it was 500c+ your laptop would have melted into liquid.
What I worry about is that why the temperature sensor have a mistake like that. My laptop had just been checked a week ago...
hello I too own R7 M360 pre-equipped when I bought lenovo z51. I've updated video card drivers along with the video card manager to 16.1 hotfix, and concurrently installed Gpu z and Speedfan, the latter occasionally reads 511 degrees, and concurrently gpu-z shows "--" as temperature. When sensor value is sensible, Gpu z and Speedfan gpu temps agree. gpu Z temp. log on time resolution t=0.1s occasionally shows a noise displaying small temp pulses of unknown magnitude, and speedfan just shows 511 degrees. A reboot fixes this situation, I tried disabling AMD drivers in device manager and enable them, yet the sensor still is malfunctioning. . I only tried driver toggle one time and waited a little less than 10 seconds.
Have you resolved this issue? Perhaps this sensor error does not occur with the original drivers, I have nothing to compare to. I am curious if more cases than just yours and mine exists for this model AMD chip, and whether this is isolated to Lenovo machines. Potentially dangerous situation. Because despite the 511 degree signal, my fan is not causing a wind. Could graphics chip actually be getting to 70 or 80 Celsius and the fan not reacting appropriately? When the sensor does work and I'm running graphics, the I've observed gpu about 20 degrees higher than cpu temps, making it risky if fan functions based more on cpu sensors.
Edit: I am now noticing the moment the video card becomes in use (max performance settings via AMD control center to ensure program runs on video card) the sensors output sensible data, and when, the graphic-heavy program terminates, the sensors shortly revert back to 511/'--'.