2008 mac pro running hot with loud fans

Discussion in 'Mac Pro' started by surfynic, Apr 26, 2012.

  1. surfynic macrumors newbie

    Apr 26, 2012
    Hi out there!

    I have a 2008 mac pro
    2 x 2.66 dual core xeon
    10gb 667mhz ddrs ram
    ati radeon hd 5770

    the other day i woke it up from sleep and the fans started blaring! i shut her down, started up again, and they were still cranking full pelt. i then turned it off over night and the next day, and for about a week, she was fine. Then after been asleep again when it came out of sleep they started up again. now they will not stop, as soon as i push the on button i hear them rev up and keep going.

    ive run istat and both processors are reading 126deg c and fans are running near on 2900. and this is the temp as soon as i turn it on and it doesnt change..

    ive opened it up, pulled it completely apart and cleaned every last bit of dust out.

    Ive checked for programs and theres nothing using the processors.

    Ive reset smc.

    ive used onyx to clean and repair.

    so now what?? im at my ropes end without any idea!! so if anyone out there can help... please please please!!
  2. flatfoot macrumors 65816

    Aug 11, 2009
    Those CPUs have a temp threshold at which they will just shut off that is way lower than the temp readings you're getting.

    Make sure the sensor plugs of the CPU heat sinks are plugged in properly on the motherboard. You'll have to disassemble the innards as if you were going about to replace the CPUs – except you don't have to take off the heat sinks.
    There are several picture/video guides on these forums on how to do that.

    Other than that, I have no idea what might be wrong except faulty sensors.
  3. kromekat macrumors member


    Jul 5, 2006
    Just checking, but did you clean all around the RAM properly? - my 2006 Mac Pro was doing that for ages, and finally I pulled out the RAM to find it was full off fluff and its been fine since.
  4. surfynic thread starter macrumors newbie

    Apr 26, 2012
    yep ive opened it up and cleaned every bit of fluffy dust build up from everywhere and it made no difference so im still stumped!
  5. ecorb macrumors newbie

    May 22, 2012

    I've been trying to correct the full-speed fan syndrome on my mac pro (2008 2.8 quad core) for months now. I finally downloaded and installed iStat, then saw that the "Northbridge" temperature was way higher than any other temp (it typically ramps up from 140 to 259F).

    What fixed it finally was simply disconnecting and reconnecting the northbridge heatsink-to-motherboard connecter (simple two-prong connecter just left of center in this photo: http://forums.macrumors.com/showthread.php?t=544597&page=2).

    Perhaps a weak connection there led to erroneous resistances and a false temperature reading.

    The connecter is accessible by just taking the side panel of the computer off and removing the video "card".

    The Northbridge temperature is now stable around 122F, more in line with the other temps.

    It's kind of embarassing what I went through in the way of troubleshooting, but let's just say I wish I'd started with iStat six months ago.
  6. nambuccaheadsau macrumors 65816


    Oct 19, 2007
    Nambucca Heads Australia
    Using that memory tells us it is a Mac Pro 1.1.

    Use a flashed ATI Radeon HD4870 with 1GB memory and the fans ramping up are something that seems to happen when coming out of sleep once a month or so. Thinks it is the gfx card causing this.

    Shut down as per normal, unplug from mains for 30 seconds or so to reset the SMC and great for another month.
  7. stupidassdrumer, Sep 7, 2012
    Last edited: Sep 7, 2012

    stupidassdrumer macrumors newbie

    Aug 20, 2010
    Any one have a picture of where this is located on a 2010 Dual Processor? I've been having the same issue where my temps are ok, except Northbridge is 162F and CPU A&B usually hang around 115F w/ no programs running. Something is for sure wrong. I wanted to try this first before I shlep my MacPro, by subway to the Mac Store in Manhattan from Brooklyn w/ out getting robbed lol. My fans cycle between 1000-1500 rpm a few times and then goes pretty quick from 2,3,4, up to 5000rpm.
  8. DanielCoffey macrumors 65816


    Nov 15, 2010
    Edinburgh, UK
  9. stupidassdrumer, Sep 8, 2012
    Last edited: Sep 8, 2012

    stupidassdrumer macrumors newbie

    Aug 20, 2010
    With out a doubt, except thats $30-40. Especially if the symptoms don't happen while its plugged in at the store, then im SOL $60-80 round trip. Doesnt seem like much to most, but I just moved here 4 months ago from Arizona. The cost of living is insane here compared to AZ, and w/ out a job every bit of $counts. Thats y id rather DIY it first.
  10. DanielCoffey macrumors 65816


    Nov 15, 2010
    Edinburgh, UK
    Fair point.

    Can you cadge a two-way lift from a friend in return for beer/pizza/yardwork? Anything to avoid handing over $$$ but preventing the loss of your Mac...
  11. stupidassdrumer macrumors newbie

    Aug 20, 2010
    hahaha! Good point! Possibly family that lives about 45mins away next time they come down here. Honestly, coming from having a great car in Arizona, I kind of miss the convenience with transporting objects. However, the subway system in NY is amazing.

    Hopefully ill find a DIY fix. Then when the opportunity comes, ill bring the MacPro to the Apple Store.
  12. kendall69 macrumors regular

    Sep 1, 2011
    I took it into apple and they fixed it for free - known problem
  13. stupidassdrumer macrumors newbie

    Aug 20, 2010
    whats the known problem? Do they know the fans run full blast randomly? Is there a specific name for the problem that I can mention to the "genius" so he/she knows exactly what to do? Did they fix it quickly in store while you where there or did you have to give it to them to fix over multiple days?
  14. stupidassdrumer macrumors newbie

    Aug 20, 2010
    I think I fixed my fan issue going full blast. After tons and tons of reading, I figured id try to see if my northbridge cable/plug were loose. I took the daughter board out and took needle nose pliars to the plug. I didnt unplug it, just pushed it down. plugged it all in and so far (24 hour later) it hasnt happened again. I havent left it un-attended as I fear it may happen that moment when I decide to render overnight. The booster fans only go as high as 1200rpm consistantly, which still may be a little high as ive seen most ppl have their fans hang around 500-800 like the rest of my fans do. The northbridge temp is still up 160F but the fan isnt going 5000 RPM anymore :rolleyes:

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