1st Gen MBP runs at 120C, does not shut down

[WillieWildcat]

Hello all, I'm a big fan of the site and I recommend it to everyone.

My 1st Gen MBP gets up to around 120C while running Handbrake and seems content on melting itself. I had this problem a year ago and Apple replaced the logic board. My AppleCare has since expired.

I tore the laptop apart and regreased the processor, videocard etc. I found it odd that there was not any grease between the heatsink and the laptop case but I did not add any. My roommate's computer is also a 1st gen and he runs handbrake daily without issue.

Any help would be greatly appreciated. I am currently running Apple's extended hardware tester, so I'll be able to answer any questions that the hardware tester might report.

Thanks in advance,

WillieWildcat

 

[spinnerlys]

Are the fans spinning?

 

[WillieWildcat]

Yes, SMC reports that they are running 6000rpm. I believe it too, I bet my neighbors can hear them running.

 

[spinnerlys]

And then it is still 120°C (393 Kelvin) and not 120 (322 Kelvin) degrees Fahrenheit?

Wow, that sounds bad.

 

[WillieWildcat]

Yes, as in "boil water and then some" 120 degrees.

I am concerned because Intel lists the critical temperature as 100C.

 

[spinnerlys]

Yes, as in "boil water and then some" 120 degrees.

I am concerned because Intel lists the critical temperature as 100C.

I have a newer MBP with more MHz and maybe the same TDP, but even when it uses its CPU at 90 to 100% for a longer time (hours) and the fans are spinning, I only get 75° to 85° C, so yours seems to be broken somehow.

 

[ttran88]

yeah. thats not normal at all. on a bad day my mbp runs at about 80 C. Hey atleast you can warm up your coffee right?

 

[m85476585]

You might have bad thermal paste.

What NOT to do (straight from an old Apple repair manual, I think):

The correct amount of thermal paste is about the size of a grain of rice (uncooked). You can replace it yourself with this:
http://www.newegg.com/Product/Produ...&cm_re=arctic_silver_5-_-35-100-007-_-Product

It is somewhat tricky to take the computer completely apart to access the CPU and GPU, but it is possible. Ifixit's guides should help you.

When you get the computer taken apart, carefully clean off the old thermal paste and apply new thermal paste. You can find instructions on the internet for cleaning the old stuff off, and Arctic Silver 5 has detailed instructions for applying it on their website.


It is not good for your CPU to operate over 105C (or whatever the spec is for your CPU). The CPU should protect itself by either throttling down or shutting the computer off so it isn't destroyed by the heat, but it is still not good to run it that way.

 

[WillieWildcat]

I am a bit more adept than your average forum poster. I used the correct amount of thermal paste and yes, I know that the processor is supposed to shut it self off at its critical point. I appreciate the help, though.

 

[ayeying]

I am a bit more adept than your average forum poster. I used the correct amount of thermal paste and yes, I know that the processor is supposed to shut it self off at its critical point. I appreciate the help, though.

You might just have a bad diode sensor.

 

[WillieWildcat]

You might just have a bad diode sensor.

Hey, there's a suggestion! Any idea how to test that or where to find a new one?

 

[voyagerd]

I took my MacBook Pro apart and washed out the heat sinks since they was caked with dust. After putting new thermal paste on, and putting it back together, it runs at 85C at 4000RPM instead of 92C at 7000RPM which is so much quieter.

 

[m85476585]

I am a bit more adept than your average forum poster. I used the correct amount of thermal paste and yes, I know that the processor is supposed to shut it self off at its critical point. I appreciate the help, though.

Sorry, I didn't see that you mentioned that in your original post.

I don't think there is any way to replace the temperature sensing diode. If it's on the die, it's impossible. If it's on the motherboard, it's probably under the CPU, and that would be essentially impossible to access since you would have to desolder the CPU.

Read the Real Temp documentation. It provides some background on how Intel's thermal monitoring works, and how to get accurate readings from it.

Do you have any way of measuring the actual CPU temperature, such as an infrared temperature gun or temperature sensor probe on the top of the heatsink where it touches the processor? (Don't run the computer without the heatsink attached!)

You could also try getting the computer very cold (put it in the fridge or freezer for several hours), then turning it on and watching the temperature reading. The best way to do so would be to put it to sleep, then wake it up when it is cold so you can see the temperature before the CPU/cooling system has a chance to get too warm. If you get readings somewhere between the freezer temperature and room temperature, the sensor might be OK. If you get a high reading (40-60C, maybe) right away, that could mean the sensor is just off by 10-20 degrees. Just be careful doing this since humidity in the air can condense on a cold computer; attempt at your own risk.