There's one step that hasn't been mentioned and is very important, especially with today's aluminum cores. After you've flushed the system with the hose you really should close the system back up, fill with distilled water, and run the engine with the heater wide open for 20-40 minutes. Then drain and add your coolant. Regular water contains many different contaminants, including metals, that accelerate the electrolysis process which aluminum is particularly sensitive to. Also, if it can be avoided, never add non-distilled water to top off the system. If, for some reason, you must add non-distilled water you really should do a system flush as soon as it's feasible.




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The effects of electolysis are not short-term. It could simply be the difference between a radiator lasting 800,000 miles or 1 million. KW had a service bulletin out in the last few years regarding this. I know that ever since I've been driving I've been told that you only put distilled water in your car. The pitting that you find in a junk radiator core is caused by electrolysis as is the pitting you find on a cylinder. I'm not saying that tap water won't work just fine but I guarantee that a radiator that has never seen tap water will outlast one that has, significantly.
