Just had to have the water pump replaced on my fiance's Sable because the impeller blades had corroded off. The mechanic that did the job for me told me that when you have troubles with rusty coolant and corrosion, you're supposed to run 100% coolant and NOT add any water. He said that the water is what causes the corrosion and that using 100% antifreeze will give you the best corrosion resistance. I ran that by a few of my other buddies and they think that using 100% coolant might compromise the cooling system efficiency. They say that adding water to the system is what makes the boiling point of the coolant go up and they suggested that I add some water to the system despite what the mechanic told me. I've never heard of using 100% coolant before and I'm just wondering if any of you guys have ever heard of this and what your thoughts are.