Quote Originally Posted by RubberDuck View Post
According to --> MaxxxRacer's Water Cooling Guide: The basics An Introduction to Watercooling your Computer <--

1. Flush the radiator with distilled water. I suggest getting 2-3 2.5gallon jugs and just start pouring about 2.5-3gallons of distilled through the rad.
2. Pour Distilled or De-Ionized water into radiator. - Pour until full, drain and repeat. Shaking the radiator when it is half full of water will help. Repeat this 3-5 times.
3. Following the same procedure as in step 2, repeat with vinegar.
4. Fill the radiator with vinegar, and let it sit for appx. 1 hour.
5.Flush the radiator, following the procedure of step 2. Repeat Step 3 as well.
6.Repeat Step 4.
7.Repeat Step 2.

Also says
I have updated the guide to limit the soaking of components in vinegar for no more than one hour. A tale-tale sign that vinegar is eating your copper components is a blue tinge to the vinegar, which is caused by copper ions being dissolved into the vinegar.
I'm fairly certain that both of those are slightly outdated. Any rad that is RoHS compliant does not require vinegar for cleaning as the flux used is very different. Also. any non-RoHS rad that has already been cleaned does not need to have vinegar run through it again. Only boiling water is needed for both of these scenario's.