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I have some non-trivial problem. If my notebook stands on solid surface everything is fine, but if I put it on my knees (for example, it could be a book too) or just push the center of the bottom cover, the CPU usage immediately grows to 100%. It also causes issues with the WiFi.

I have MacBook Pro mid 2010, which I manually upgraded to an SSD (optibay) + 8Gb DDR. I recently disassembled it and cleaned it, but the problem came yesterday. I tried to manually push some points on motherboard but failed to reproduce the problem, it only occurs when pushing the bottom cover.

In Activity Monitor, kernel_task is using greater than 170% CPU. There are no warnings or errors in logs during this problem.

Has anyone else seen this? What can I do (other than going to a service center)? What kind of problem could it be?

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UPDATE

I've done messy solution - place the steel coin between the bottom cap and the processor's fan. Now the bottom cap did not contact the cooler and everything's fine.

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  • Wow - what process gets the CPU time in Activity Monitor - kernel? And are there any logs in /var/log/system.log when the fault happens? – bmike♦ Oct 10 '13 at 19:24
  • @bmike No process loads greater that 1%, just 100% system load. htop shows the same. By the way, there is no warnings or errors in logs during this problem – Andrey Nelubin Oct 10 '13 at 19:30
  • @bmike sorry I was wrong. The kernel_task process is up to 176% usage. – Andrey Nelubin Oct 10 '13 at 19:41
  • What can you do to resolve the issues? Does a restart help? Are you sure that there aren't any messages posted to /var/log/system.log from the kernel process? Alternately - if you're running a system lower than 10.8.2, the kernel log may be at /var/log/kernel.log. – Eddie Kelley Oct 11 '13 at 21:50
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    Let's have you answer your question below. Adding the answer in the text of the question is strongly discouraged. Cheers that you solved it! – bmike♦ Oct 14 '13 at 7:14
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I would re-seat all the temperature sensor connectors.

I've read that when the machine appears hot, kernel_task slows the machine down in order to reduce the heat. The way it does this causes the CPU usage of kernel_task to appear high.

So perhaps, when you press on the cover, this distorts one of the temperature sensor cables, causing some faulty temperature readings. (I'm assuming the machine doesn't seem hot to you?)

I did a search for [kernel_task CPU heat] and found this blog post, which describes a way to "fix" this issue by modifying the kernel_task configuration so it doesn't take this action. I'd caution against this modification, though, as it doesn't fix the underlying hardware problem -- instead, it disables a (presumably important) software-based safety mechanism.

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  • Hello, Ashley! Big respect for your answer. I've done messy solution - place the aluminum coin between the bottom cap and the processor's fan. Now the bottom cap did not contact the cooler and everything's fine. I will try later the your solution. Thank you a lot. – Andrey Nelubin Oct 13 '13 at 16:44
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If you replaced RAM in the machine, and the computer is having issues when flexing or pressing on the bottom case, I'd recommend re-seating the memory chips.

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