Removing the CPU assembly from a G5 PPC 2.5GHZ Quad

Discussion in 'PowerPC Macs' started by jlofgr, Jan 24, 2014.

  1. jlofgr macrumors newbie

    Jan 24, 2014
    Hi Folks! Greetings from Seattle! I have an issue that I could use a little help with. I have a very nice late 2005 G5 2.5 GHz PPC that needs some new heat sink compound. I have the manual and have followed all the instructions to the letter for removing the CPU/water cooling assembly from the case, but it won't lift out. Something is holding it down at the radiator end of the assembly. All bolts to be removed, have been...all bolts to loosen, have been. Still, no joy.
    Anyone have any information to share on this, I would really appreciate it. This is a cool machine and I plan on working it.!

    Jim, in Seattle.

    Two-Way Tech, Accordion Player/teacher, Trying to figure out how to retire...:)
  2. Pkupman57 macrumors regular

    Apr 18, 2013
    El Lay, CA
    If you have all 8 screws loosened/removed... then it should lift out. You said its hanging on the radiator side, you got the two screws on the outer edges on the "outside" of the radiator, right? These are older computers though, so you might have to give it a little bit of effort. I had to basically yank mine out, as it didn't come easy. They have been sitting, assembled, for the better part of a decade now...

    Is yours a single, or dual pump model?
  3. jlofgr thread starter macrumors newbie

    Jan 24, 2014
    Those two screws are removed. There are screws under the ends of the radiator, but not accessible with a torx. I assume that plate has to stay with the chassis. I tried some light prying between the piece with the fan connector and the CPU Base plate to no avail. So, your recommendation is to just drum up the courage to yank it out? What is under there that could get stuck? It seems to be in the region of the many-pinned connectors. Thanks for the input! I may wait for a second opinnion before I go crazy....Jiim
  4. jlofgr thread starter macrumors newbie

    Jan 24, 2014
    Another note on this particular went back to Apple in 2006 because it was leaking and had damaged a processor. I wonder if apple did any extra work beyond the original spec when they repaired it.

    I tried yanking it and lifted the Chassis 3 inches off the table. I believe I will remove the drive bay across from the radiator and get a little prying leverage on that side of the assembly while lifting on the other end. Comments>
  5. jlofgr thread starter macrumors newbie

    Jan 24, 2014
    It is out!!! Followup for future use....I didn't loosen the 4 screw next to the radiator enough to allow the unit to come free. My Bad. It is important that those 4 hex screws get loosened until the threads have completely released. The good news here is that there is no leakage whatsoever. As I said, this unit went back to apple in its first year with a catastrophic leak failure and I wonder if they hadn't done some more extensive work to seal it. Thanks for the help!

  6. jlofgr thread starter macrumors newbie

    Jan 24, 2014
    Now that it's done....G5 Cooling overhaul +

    Just a few notes for those that follow.... After pulling the CPU assemblies and cooling chassis, I found no! leakage at all. That's the good thing! Removing the eight screws that hold the CPU's to the cooling blocks was a little challenging. This is a late 2005 machine and was repaired at Apple in 2006 for leakage damage. They sealed it up pretty well, but the threads on the bolts that hold the cpu's tight to the cooling blocks were a mess. Would never go all the way back in. I ended up retaping the blocks for 6-32 screws and used Stainless flatheads, 1 1/4 " long. Then back nutted them on the top of the blocks so they wouldn't come loose since they didn't have any shoulders. I used a straight edge to make sure the tops of the bolts were flush with the top of the cups that they extend through. It worked out very well! I used 3/8ths x 5/8" Primochill tubing to avoid kinking...worked well also, but I did re-rout the tubing, after its "T" on the way to the pump inlet. I took it around the "A" processor ports which extended its length but made less tight bends. The Side A filter was blocked by deposits, so I cleaned that out, cleaned out the B filter and soaked the radiator in 50/50 white vinegar and water. Three flushes thru it, then overnight in a solution of it. I got the "O" rings at the neighborhood autoparts store......1 3/8ths by 1/16th if I remember right. I did learn something new....I tried to use the old processor screws, but I couldn't seat a couple of them flush with the tops of their cups. They were maybe 1/32 to 1/16ths about the tops of the cups. That's why I ended up using 6/32 bolts. That was enough to not allow the CPU connectors to seat and the machine didn't like that at all when I fired it up. So there you have it. A=40 degrees at an idle B=41 degrees idling. Machine is actually quite civil now. Fan never speeds up, Goes to sleep, stays asleep and wakes up on cue. I couldn't be happier. Oh, I did us EK ECoolant and seems to be fine. Seems that distilled water is the called for when flushing and rinsing the radiator. Any questions, I would be glad to answer. Note..this isn't an inexpensive process when you consider all the pieces. Clamps alone were $16.00. Coolant: $20 (with postage). Tubing: 5' @ $3.00 per foot. As far as I'm concerned, well worth it but be prepared to do it right.
  7. robertdsc macrumors regular


    Jan 28, 2014
    Great work. Thanks for the updates.

    I would love a Quad but the cooling system scares me, lol.
  8. tevion5 macrumors 68000


    Jul 12, 2011
    Thes are digits in machines to disassemble! There are screws in places behind other things that require a touch of magic to get out.

    I needed a big long snake of a flex screwdriver and even then it nearly drive me insane! I repect anyone who can beat the stress long enough to reach full dissassembly! :p

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