Chosen Solution

I live in Pakistan where my city gets average of around 40℃ in the noon. While using my device at noon I’m getting 70℃ cpu temperature, at idle load(no apps running) is this temperature alright or too high? Screenshot while using just safari: Screenshot few seconds after startup:

screenshot while playing the default chess game:

screenshot using safari:

@danj i just ran a cpu stress test (all 8 cores) and the core 1,2,3 run at 103 while core 4 runs at 96. could that indicate a processor problem? heres a screenshot:

Looking at the tg pro main windows:

the max temperature for core 4 is lower than all others

If I didn’t know what else was at play here I would say this system was running hot. The things I look at is the running processes under Activity Monitor to make sure something isn’t running wild (malware or someone has rooted the system). The next thing I look at is the fans to make sure they are working correctly. I use this App to do that: TG Pro (full version). It does a better job of monitoring the thermal sensors and the fans than most everything else. I often end up cleaning the dust build up in the fans as well as the logic board. In your case you may need to replace the fan units to the ones the logic board you are using would require. The next thing is checking the heat sink heat pipe to see if it is transmitting the heat. I use a non-contact thermal probe to review the pipe from CPU and GPU to the fins. The heat should be fairly close to the same. If not the cooling liquid has leaked (sometimes you can see the wetness on the logic board). To verify I take the heat sink off clean it and then using a pharmacist scale I compare it to a known good unit (same P/N) the bad unit should weigh less. After which I clean the old thermal paste off of the CPU & GPU’s and apply a fresh coat of a good quality paste. I use Arctic Sliver as well as the cleaner they offer. Update (08/21/2016) Here’s what my MacBook Pro looks like running Safari:

As you can see its much lower. I was hoping you would have snapped the full display like this so we could have see the RPM numbers. But since you gave us the values its clear you do have a transfer issue with the heat sink. So you’ll need to start there.