Is it me or is it hot in here? iMac overheating?

Discussion in 'OS X Mountain Lion (10.8)' started by bodkin, Jul 30, 2012.

  1. bodkin macrumors newbie

    Sep 20, 2011
    I have a 21.5 inch, mid 2010 iMac with 12Gb RAM and since installing ML my mac seems to become really hot. If I run my hand over the top of the machine the centre and left corner are really hot. Not just warm but sometimes nearly too hot to touch. ML has been installed now for 72 hours. Has anyone else noticed a huge increase in housing temperature since upgrading?

    Is this heat excessive and likely to damage my iMac?

    I think the problem of not being able to 'sleep' without losing network connections (so being left to run permanently) is exacerbating the problem.
  2. GGJstudios macrumors Westmere


    May 16, 2008
    The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C (221F), GPU Tjmax = 100C (212F) on i3, i5, i7 processors. (Source: Intel) If you're not already using it, iStat Pro will give you accurate readings of your temps and fan speeds, among other things.

    Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.

    It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.

    Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). iMacs have 3 fans with minimum speeds in the 800-1200 range. They will spin faster as needed to keep temps at a safe level. If they're spinning up without increased heat, try resetting the SMC. (PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)

    The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks (except the new MBP with retina display, which has intake vents along the sides at the bottom). The iMac vent is a slot on the back near the top of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best.

    Learn about the fans in your Mac
    Apple Portables: Operating temperature

    For Flash-related issues:
  3. dweissma macrumors newbie

    Aug 7, 2012
    Same problem: overheating iMac with ML

    I have the same machine (mid 2010 21.5" imac) that has overheated since I upgraded from Lion to Mountain Lion. I don't think it's normal overheating. It never occurred with Lion. I wonder if I can do a full restore of Lion from my Time Machine backups.
  4. Tander macrumors 6502a


    Oct 21, 2011
    Johannesburg, South Africa
    If the machine is overheating - it will shut down. If it hasn't done this and is still operating as normal (besides the extra heat) then no need to go back to an outdated OS?
  5. dweissma macrumors newbie

    Aug 7, 2012
    Ok. Thanks for the reassurance. I'll stick with ML for the time being, having installed smcFanControl so at least I can see how hot is hot. I wasn't looking forward to trying to restore an old OS. But it still does concern me that the machine gets so hot with ML. Is there really a bug in ML that causes this? Will there be a patch for it? (These are sort of rhetorical questions.)
  6. Tander macrumors 6502a


    Oct 21, 2011
    Johannesburg, South Africa
    It may just be a bug in the OS or maybe ML is working the machine a little harder. Either way, I would't be too concerned about it. Just monitor it and see how it goes.

  7. kodeman53 macrumors 65816

    May 4, 2012
    Getting warm/hot does not = overheating.
  8. Mr. Retrofire macrumors 603

    Mr. Retrofire

    Mar 2, 2010
    This happens usually, if you install OS X 10.8.x over OS X < 10.8.x. Some Lion users had the same problem. A new installation should help.


    That is probably your problem.
  9. Tander macrumors 6502a


    Oct 21, 2011
    Johannesburg, South Africa
    Please explain why an upgrade from 10.7 to 10.8 will warrant the extra heat as oppose to a clean install?
  10. pbrooks macrumors regular


    Jul 15, 2008
    I'd like to be educated on this, too.

    I'm really sick of the "clean install" intelligentsia. I have migrated from Panther to Mountain Lion without ever doing a clean install, and I NEVER (and I mean NEVER) have had any of the issues people complain about here outside of documented bugs which have always been fixed in subsequent software updates.
  11. thermodynamic Suspended


    May 3, 2009

    Damage is possible, or at the very least a reduction in long-term lifespan due to constant hot conditions.

    Mountain Lion must be a complete re-indexing of the system, or doing something very processor-intensive. With luck it'll cool down over time, but if you have SMCFanControl and can up the fan to 5000RPM or whatever the max is, until it's done processing, anything to keep the temperature down is going to help.

    Computers can operate in warm conditions and get hot, but while they can tolerate up to a certain condition, they are not designed to run at that temperature, constantly, for a period of time.

    The 2009 iMac I had sold had its buyer contacting me 2 years later due to the (common) screen burn problem due to overheating within.

    The CPU can run at up to 105C (before it shuts down the system, complete with fan that - in turn - won't channel out because it's stopped spinning and damage could still result), but it's the same commodity Intel CPU that didn't shut down a Dell and fried as a result. So, no, I don't trust Intel's thermal override function either.

    These chips are not magical, and because they're Intel, anyone on any Intel forum - especially if they overclock for Windows - will quickly tell you about the importance of cooling.

    Worse, aluminum acts better as an insulator than plastic. Macs use aluminum and because the chassis does not touch the CPU directly, it acts more as an insulator than a conduit for heat removal. Many people have opened up their Macs and applied proper amounts of higher quality thermal grease, or added holes in their cases (MBP or iMac) to improve airflow. (All that voids your warranty and don't blame me if you try doing any of that...)


    True -- getting hot isn't overheating but, false, that doesn't mean anything adverse isn't happening as a result.

    Nice sig line, BTW... most people these days, regardless of political party affiliation, are more interested in their own businesses' survival than anyone or anything else...
  12. Mr. Retrofire macrumors 603

    Mr. Retrofire

    Mar 2, 2010
    Some old software runs in the background, the system loads preferences from incompatible .plist files. Spotlight indices are probably not compatible, which causes repeated indexing and higher heat and so on.

    I agree, you are sick. :D

    You are not the world. Some people solve their problems with a clean installation. That is a fact.
  13. BruceiD macrumors member

    May 1, 2012
    Yup same here
    Exact same model (also with 12GB RAM)
    My iMac gets at least 10 degrees Celsius hotter then it was with SL or Lion..
    Oh well I'm using SMCFanControl till a fix.
  14. Stonefly macrumors regular


    Dec 26, 2009
    Nova Scotia
    I've got a late 2009 27 inch iMac. Mine ran hotter than SL and Lion to. My cpu fan was about 3000 rpm while just surfing the net. I did a full restore back to Lion using a time machine back up. I may try a "clean ML install" this weekend to see if it works better.

    This was interesting, didn't know that. Thanks Mr. Retrofire

  15. danieledmondson macrumors newbie

    Dec 31, 2012
    "the temps are well within the normal operating range"

    I am sick tired of hearing "the temps are well within the normal operating range, considering the workload being put on it."

    I have purchase new mac ever 3 years for the last 28 years and I know how hot a apple should be running and this is not normal. I have taken my mac in 4 times for the same reason running to hot since 18 th of Jan . and apple still has not fixed it. They just tell me it is with in parameters. Two weeks ago I checked it temp after watching Hulu for 2 hours and it was 107 degrees and the temp in my bedroom was 21 degrees higher then the rest of the house. I live in Tucson Az. and we do not have heat in the house. The living room temp was 70 degrees at 1:30 am and my bedroom temp was 91 degrees and the only heat source was my computer. 45 min after turning it off the bedroom temp dropped to 70 degrees. Then there is the finder problems when it gets hot , I have to try an copy three - four times and then I might get luck and it will pick it up and let me paste it. You can forget about moving folder around will it is hot. It seems like any thing to do with the finder starts acting up when the temp goes up.
    Oh then there is the fan it seems to never run, our it runs like a jet engine never shutting down for hours on end. I am about to just give up

    After 25 years I think it is time to buy a PC.
  16. simsaladimbamba

    Nov 28, 2010
    I presume you use Fahrenheit as scale? Remember, this might an US centric message board, but not everyone posting here uses such an outdated scale.

    If so, those temperatures are within the norm and specs of the used hardware. Check post #2 for those specs.

    I have a 2007 iMac, which normally idles around 45° C (113° F), under load it gets to 65° C (149° F). These temperatures are within spec/norm of the C2D CPUs. My 2009 MBP idles at 60° C (140° F) and under load goes up to 95° C (205° F), again within spec/norm.

    Flash us CPU intensive and the temps you read are normal.

    A PC tower has more room to ventilate, thus you might see lower temperatures, but only within 10 to 20 K (I guess, Kelvin cannot be applied to the Fahrenheit scale, no wonder, Fahrenheit is such an illogical scale).

    If a Mac overheats, or any modern consumer computer, it shuts down. As your iMac did not shut down yet, it is operating normally.

    But then again, you are "sick and tired" of hearing this. So, what do you want to do?
  17. GGJstudios macrumors Westmere


    May 16, 2008
    You may be sick of hearing it, but it's still true.
    There is no way a single Mac is going to raise your room temperature by 21 degrees, unless your room is the size of a microwave oven, has zero ventilation and you leave your Mac running at full tilt for hours. Even then I doubt it would raise it that much.
    Your Finder issues are more likely related to the load on your CPU/RAM rather than heat.

    Rather than make assumptions, install iStat Pro (free) or iStat Menus ($16) to get accurate readings of your temps and fan speeds.
  18. KootenayJim macrumors newbie


    Jan 17, 2008
    british columbia
    2008 imac w mtn lion crashing

    Hi Macaholics
    My imac goes dead with glowing black screen and seems very hot , just surfing w firefox and on FB. Temp was over 146F I think. I thought it maybe was the screen saver grabbing a blank black picture so changed into the imac pics but still crashing every day or so.
    Going to vacuum the ports and put a little fan v behind it, but it seems to get intensive now and again and overheat
    My orig HD failed [ was getting hot and erratic glitches]and so got a newer bigger HD from dealer but this shouldant be happening dont you think. :confused:
  19. GGJstudios macrumors Westmere


    May 16, 2008
    Read the 2nd post of this thread, especially the info about Flash. 146F is well within the normal operating range.

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