Coolant recommendations for a mixed metal loop

Hi everyone:

My buddy gave me his Power Mac G5 2.7 Quad computer the other day. Since current versions of Mac OS X won't run on it, I am planning to install either Debian or Gentoo Linux on it, pop in an old 3Ware 8 port raid card and 8 x 500gb laptop hard drives. I will use this for a file/minecraft/media server for my home.

On initial teardown and inspection, I discovered that the system was water cooled, (my friend did not know this after 8 years of use), and that the water cooling system had been leaking for some time. It had lost about half of it's coolant, (The recommended fluid amount was 180 ml and I only drained out 83 ml). I also found out that for some reason, Apple had decided to use an aluminium radiator and pipes with water blocks that are made out of a nickel plated base with copper fins attached. I have cleaned the system and I am ready to reassemble it, however I thought I would solicit opinions and recommendations for fluids. Mac's spec sheet calls for 66% distilled water and 33% glycol, (antifreeze).

Does anyone have any suggestions for a better coolant?

Thanks

zog

Glycol is what keeps nickel, copper, and aluminum from reacting with each other.
I would follow their spec sheet.

Generic glycol is not, strictly speaking, automotive antifreeze. The glycol changes the boiling and freezing temperature of the fluid only, and does not impart corrosion protection or pH stability properties as far as I understand it. Those properties come from other chemicals in automotive antifreeze. It's the glycol that reduces the heat transfer ability, and thus effectiveness, of the fluid in a cooling loop, however. Thus it's entirely possible to create a coolant additive with pH stabilizers, corrosion inhibitors, and a surfactant. In a nutshell, that's what most coolant "wetting" or coolant improver type products are.

I've been very happy using this: Amsoil Dominator Coolant Boost

Ignore all the marketing puffery about it improving temps, I don't really buy it even though my water loop does perform extremely well. What really impressed me was the corrosion tests on the bottom of that page. Even distilled water results in some copper corrosion. More than I would have initially suspected, matter of fact.

Other nice things about it are that it doesn't stain plastics and tubing the way that Red Line's Water Wetter does due to using a different surfactant. Plus the fluid actually goes from red/purplish to clear as the pH buffers get used up, thus signifying the need to change the fluid. The surfactant also aids in bleeding all the bubbles out of the system.

I use that, mixed per directions, and the proper amount of copper sulfate, again added per directions, to a 50/50 mix of distilled and regular bottled water. Amsoil says not to use pure distilled due to whole "hungry water" thing, but I couldn't bring myself to do it. I'm pretty sure you could get away with regular distilled though.

I've been very happy using this: [url=http://www.amsoil.com/shop/by-product/other-products/antifreeze/dominator-coolant-boost/?page=%2fstorefront%2frdcb.aspx said:

Amsoil Dominator Coolant Boost[/url]

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Thanks a lot! I just found a source online, I will give it a try.

Other nice things about it are that it doesn't stain plastics and tubing the way that Red Line's Water Wetter does.

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LOL, I haven't used Water Wetter for years! I think I still have a Danger Den block from an Athlon slot A system that is STILL dyed red from that stuff!