I have done two machines with no ill effects, reducing the temperatures in one case by nearly 10°C.
The liquid cooling seems to work well. Wow. I have used three air-cooled dual G5s, and they all do get up to those numbers. My dual 2.0GHz at work is constantly in the high 50s or low 60s, meaning the fans do kick in. Both the decommissioned dual 1.8 and the new-to-me run cooler and more quietly, for some reason.
Pop rivets! Now, if it were a liquid cooled 2.7, you really would want to go carefully, but I assure you there aren't any pop rivets in a 2004 G5 to worry about -- except maybe the plastic one on the cover inside the plastic door! Further inside, once you get it apart, there are screws holding the heatsinks to the processor boards, located at the edges, and there is ordinary heatsinks compound. That's it.
Yes, I know what the service manual says, but Apple service manuals also say that on no account should you install a RAM chip in a Classic II, or whatever. I was nervous, too, but I began with a G5 that did not work and figured I had nothing to lose. I fixed it so that it worked fine (under Tiger). That worked so well, I did the same when another machine came my way, though with no discernable benefit in the second case. I am now on my third G5 tower, and it works fine, so I propose to leave it as is.
There are lots of discussions elsewhere about disassembly that confirm the approach taken. However, it's not yours, and the, 'if it ain't broke, don't fix it' maxim would seem a useful one in this case. You have sorted the USB issue, which is the main thing.
However, you can buy a replacement processor these days for a song, were things to go haywire....
Last edited by beachycove
on 01 Dec 2011, 04:27, edited 1 time in total.