Thanks to everyone for their comments.
Still, I will no longer recommend it: there are too many variables for a newbie to get into something like that.
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Windshield wiper fluid is an EXPERT/ADVANCED solution, only for those that understand the safety precautions that are required.
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to 000: there are many ways to seal a system. If you have an intake in your rig, and you cap it off, then you can easily refill it. Also, as I've suggested before, if you put a T at the pump inlet, and put a ball valve on it, you can let the coolant out of the system through a hole at the bottom of the case. All you have to do, is prop up your computer, and turn the valve.
To answer your questions, if you're going to modify your rig, you should drain it first, and rinse it out, then you can take it apart any which way you want. I'm not sure what you mean by "direct contact". If pressure buildup is a concern, then you can add a flexible component to your res (like a balloon).
To myv65: I'm not going to minimize the risk here. I know better than to go against typical industrial applications. If they condone it, then I'm not going to recommend it. (not to say that I wouldn't consider using it myself
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