Late 2011 MacBook Pro: GPU Diode displaying absurdly low temperature?

[Crimson Hikari]

I recently took apart my very out-of-warranty late 2011 Macbook pro to clean it out and replace the thermal paste (it was starting to sound like a plane when I played stuff on Steam). This was an apparent success because combined with cleaning out the fans (where there was a LOT of fluff), the temperatures have dropped fairly dramatically.

However, the GPU diode in iStat Pro on the dashboard are now reading a very low number (anywhere between 1-20C) or going into negative numbers like -127-128C. This is only for the Intel 3000 GPU. The discrete graphics card reads around the same temp as the GPU itself and appears to be fine.

Can anyone explain what caused this? I've taken it apart before and not had this issue?

 

[TheIguana]

Best guess is the GPU temp diode was either on its way out and the thermal paste replacement did it in or it failed upon application of new thermal paste. Probably not too big of a deal as the system still has the main GPU and CPU temperature sensors to indicate if an overheating event is occurring.

This was an apparent success because combined with cleaning out the fans (where there was a LOT of fluff), the temperatures have dropped fairly dramatically.

Out of interest, why did you replace the thermal paste before first cleaning the "fluff" out to see if this rectified the "sound like a plane" symptoms? As a cursory observation, dust build up is likely to have a much higher impact on temperatures than the thermal paste.

 

[Crimson Hikari]

Best guess is the GPU temp diode was either on its way out and the thermal paste replacement did it in or it failed upon application of new thermal paste. Probably not too big of a deal as the system still has the main GPU and CPU temperature sensors to indicate if an overheating event is occurring.



Out of interest, why did you replace the thermal paste before first cleaning the "fluff" out to see if this rectified the "sound like a plane" symptoms? As a cursory observation, dust build up is likely to have a much higher impact on temperatures than the thermal paste.

I had cleaned up the fans before (about a year ago when the issue wasn't too bad), but it hadn't particularly made much difference. A friend had some spare paste after a recent build so I gave replacing it a shot, and the two combined caused the CPU temp to drop 9C while moderate web browsing (before around 55-60C, now averaging between 45-50C). While gaming it's caused about a 5-8C drop.

Not chalking it up to just the paste (first time applying new paste, so I could have seriously fudged it up) but my application was probably a lot neater than Apple's was; when I took it apart and cleaned the old one off, it looked like grey congealed mayo that had oozed out of a squashed sandwich then been left for 6 months...it was everywhere.

I was just concerned I'd damaged something fairly important. But if it really won't make that much difference, I won't worry too much about it.

 

[tnicely83]

I just did the same thing for the same reason to my MacBook Pro 2011. I am having the same issue, so I just wondered if you ever figured out why it is goes from 1-20c to 128c??? I think my Mac is running a lot cooler, but I did notice mine is showing the same temps as you stated.

I had cleaned up the fans before (about a year ago when the issue wasn't too bad), but it hadn't particularly made much difference. A friend had some spare paste after a recent build so I gave replacing it a shot, and the two combined caused the CPU temp to drop 9C while moderate web browsing (before around 55-60C, now averaging between 45-50C). While gaming it's caused about a 5-8C drop.

Not chalking it up to just the paste (first time applying new paste, so I could have seriously fudged it up) but my application was probably a lot neater than Apple's was; when I took it apart and cleaned the old one off, it looked like grey congealed mayo that had oozed out of a squashed sandwich then been left for 6 months...it was everywhere.

I was just concerned I'd damaged something fairly important. But if it really won't make that much difference, I won't worry too much about it.