Need help. MBP running hot and slow

Discussion in 'MacBook Pro' started by luthier42, Aug 30, 2014.

  1. luthier42 macrumors newbie

    Nov 28, 2012
    I'm looking at picking up a used 2012 MBP. The price is good, but I'm told it runs really slow and the fans run constantly. I plan on replacing the HDD and maxing out the RAM anyway, but I can't get to the machine to run a hardware test before purchase. Could this be some other sort of hardware issue (logic board)?
  2. kelon111 macrumors 6502

    Mar 16, 2013
    The thermal paste might need to be changed if the fan is on constantly.

    Is it the 15" model or 13"?

    If it has a 5400 RPM HDD and maybe 2 GB of RAM, I could understand why it would be described as slow.
  3. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    It's a 13" with stock 500GB drive and 4G of RAM


    Is it possible that this would be a logic board issue?
  4. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    The HDD is the problem. 5400rpm HDDs are just plain slow.

    Buy an SSD for it.
  5. illusionx macrumors 6502

    Jul 4, 2014
    Brossard, QC
    If the fan run constantly, the heat sink could be blocked or thermal paste should be redone.

    I recently had a similar issue with my 2011 MBP. You wouldn't believe how dirty it was inside.
  6. simonsi macrumors 601


    Jan 3, 2014
    Two possibilities:

    Something is running on the machine, maxxing out the CPU, causing it to appear slow to the user and run hot.

    Airflow blockage is causing it to run hot enough to throttle, hence appearing slow.

    A screenshot of the CPU activity monitor panel sorted with the highest CPU usage at the top will likely tell you, or you can post here, and possibly the vendor can send you before you get it or make a final decision?

    Highly unlikely to be the HDD, while they can cause apparent slowness if they are logging errors, that failure doesn't tend to make the machine run hot in my experience.
  7. 556fmjoe macrumors 65816


    Apr 19, 2014
    It won't be the problem unless it is failing, which is unlikely in a 2 year old computer.
  8. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    The plan is to get a big SSD and max out the RAM. I plan on installing the OS from scratch (you can still do that, right?) so I'm really hoping it's software related. As far as I can tell from research it's either software (resource) related, fan sensor related, or dirt. Does that really cover all the bases or is there some chance that I'm gonna have a bum logic board?
  9. simonsi macrumors 601


    Jan 3, 2014
    Unlikely based on your reported symptoms. Possible but very unlikely.
  10. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    Is anything likely to even show up in a hardware test if it were the logic board?
  11. T5BRICK macrumors G3


    Aug 3, 2006
    Yes, AHT could catch issues with the logic board.

    Do the fans run constantly even with a clean install of OSX?
  12. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    Don't know, it's an online purchase. I asked the guy if he'd do a hardware test. Waiting to see. Thanks for all the help guys. I've only ever had one Mac that had a logic board fail and I don't really remember the details.
  13. maflynn Moderator


    Staff Member

    May 3, 2009
    Seems like a number of red flags on this used MBP sale. Unless the price is really low and you can afford to lose that money on getting a defective mac, I'd walk away.
  14. Doward macrumors 6502a

    Feb 21, 2013
    I'd use the 'issues' presented to drive the price down as far as I could get the seller (and honestly, it should be a KILLER deal, as most Apple owners I know have no idea how to fix anything)

    The first thing I'd do, is a full clean and re-paste:

    Why would I do these things? Because I've done them before ;)
  15. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    Here is the only error reported from the hardware test:


    Heatsink sensor it seems.
  16. snaky69 macrumors 603

    Mar 14, 2008
    A temp sensor failing will make the computer default to full blast fans, as it has no idea whether it needs cooling or not and takes no chances.

    The sensor itself is about $20 or so if I recall, Apple should fix it for very little money.

    If by running hot the guy is just stating that the computer is warm to the touch, well that's just how MBP's are.
  17. luthier42 thread starter macrumors newbie

    Nov 28, 2012
    I decided against it. After looking at the 38 step repair at iFixit and realizing that I could get the same machine without the heat problem for an additional $70 (a good deal less when you consider the part, thermal paste, and a few tools I don't currently have) and not have to disconnect all those crazy small connections it seemed like it might not be worth the effort and risk that I might damage something in the process. Thanks for all the help guys, I learned a lot.

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