Macbook Pro 2009 820-2523-B getting burning hot



i have here a MacBook Pro 15" 2009 with 820-2523-B that gets extremely hot.

Of course I have already cleaned the vents and have replaced the thermal paste. With no improvement. I have also checked the heatsink with hot air and a thermal cam. It conducts heat normally.

Still the MacBook gets burning hot. The App Macs Fan Control shows "CPU Diode" around 80 - 90° C. The fans run at full speed at this temperature. The OS is a fresh install.

What could be the reason?


Staff member
Run corresponding ASD and see if any error pops up.
80-90 degrees on CPU die shouldn't push fans to max.


I already ran the Apple Hardware Test from the original DVD. It found no error. Can ASD detect more than AHT?


I wanted to let it run to check how many minutes it takes to get hot. Unexpectedly it ran pretty normal for 30 minutes with CPU Diode around 70°C and fans at minimum. After that I tried stressing the system with Unigine Valley, which uses both CPU and GPU. It did not get very hot during the benchmark, the fans ran only at 50% and after the benchmark was finished everything returned to normal quickly. I have no idea what happened, the problem seems gone. The day before it ran at more than 90° and fans at full speed, even when performing basic tasks. 🤷‍♂️