History

My car was parked in a parking garage and the sprinkler system leaked hard water on to the hood of my car. It was freezing outside, and has been for about 3 weeks without break, so I was not able to clean it right away. I tried to wash it off one day when the sun was out and the car's engine was hot from driving around, hoping I could wash it off with soap and water before the freezing temperatures froze the water. The hard water stains would not wash off. I found I could scratch it off with my fingernail but that wasn't helping my wax job at all. My plan was to wait for the first above-freezing day and slowly scrape off all the stains then wash and re-wax my car. This would probably mean doing it when its in the mid 30's outside; not something I'm terribly looking forward to.

Solution?

I just found this on a google search that says I can use a 50/50 mix of vinegar and water to remove the stain. I would have to mix it in a spray bottle. Spray it on. Wait a minute or two. Then wipe it off. As soon as its above freezing, or the next time I go for a drive and warm up the engine, I'm going to give it a try and update this page.

Finale

It worked! I didn't have a spray bottle so I poured some vinegar into a soup bowl. Poured some warm water into the soup bowl. Then took a wad of paper towels, dunked it into the bowl of vinegar/water and sloppily rub the wet wad of paper towels all over the hood of my car where the stains were. I let it sit a minute or two, then repeated. I had already noticed a difference, the stains were going away. A minute or two later I checked on it. I dumped some clean warm water of the area that I wiped with vinegar/water and wiped it down clean. No more hard water stains!