Leaky PowerMac G5


I managed to get a steal of a deal on a PowerMac G5 2.5 Ghz just to find out that these dual G5’s are notorious for their leaky water cooled systems. Fortunately, not enough coolant  had leaked out to ruin the power-supply, which happens to be underneath the cooling system (not a very good design).


Water cooling system removed and pump set aside. the piping is quite impressive. The amount of aluminum tubing and rubber hoses was a concern, why there was not vinyl tubing is questionable. The amount of clamps needed doubles the likelihood of leaks.


Filling the radiator and checking it for leaks.


One of the water blocks that rests on the processor, the dark grey areas are evidence of leaking.


The water block cleaned up and marked for dissembly.


The culprit: the white Teflon “O” ring.. which had warped and distorted. These were replaced with automotive  “O” rings along with RTV sealant.  The good ole’  local hardware store (not the big box chains) had these in stock.  The St. Peters True Value is a great hardware store, just like they used to be, aisles and aisles of tons of cabinets full of odd size parts and every tool imaginable.


A spare power supply shorted so it can be used to provide power with out a tower.


Power supply to drive the pump.


Testing the pump with some runs and checking for leaks. Tubing was replaced with thick wall 3/8″  vinyl (again tubing came from the good ole hardware store, pull a length off the spool and cut what you want)


All buttoned up and sealed, it took several hours to completely  bleed out trapped air bubbles, fortunately there is a bleeder valve (capped in black).

When all was said and done it runs like a champ. Cleared the PRAM put a fresh install on the system and calibrated the fans and cooling system with an Apple ASM disk and runs great now.  With some work and fun, it’s not bad for a next to nothing deal :)

4 thoughts on “Leaky PowerMac G5

  1. Robert A. Obenshain

    Have four leads on the motor plug. Need to know which leads feed the motor.
    Thank You

  2. gordy

    Hi Robert,

    Looking from the top of the plug there are four leads from what I recall i used #1 and #3 I had to experiment until I found the correct combination, I didn’t harm the motor while experimenting, by the way.

    Best of luck!

  3. Robert A. Obenshain

    Thank you for your reply. It did help me. Had a feeling that the motor was bad and it was.
    Thank You Very Much

    1. gordy

      Oh man, that’s a bummer – did you try to take the motor assembly apart ? There might just be an obstruction, whatever coolant Apple used tends to gum up (did in my case, heh literally in my case! )

      Kind regards,

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