I have almost the same problems with my Inspiron 3521, i7-3537U, 8GB, Radeon 8730. I tried every available BIOS from A04 to A09. The original BIOS was A04. The fan is running almost all the time at 5100rpm. When the temperature reach 55°C the fan start running at 5100rpm and it stops (0 rpm) when the temperature is below 46°C, but it need more than 10 min in idle to make the temperature 46°C. Sometimes it run normally at 2600 rpm in idle at 50°C, on medium load it start increasing the rpms to 3500-4000.