Dear Tom and Ray:
My aunt called me the other day and said she had trouble trying to find the place where you put more windshield-washer fluid.
She told me the only cover she found was one that said "Coolant." You guessed it — she put the windshield-washer fluid in the coolant reservoir.
She then told me that she used a bottle of Windex instead of the diluted blue stuff you buy for car windshields. What should I do to help her, and what possible damage did she do? —Adam
Tom: Well, the first thing you can do to help her is open her hood and show her where the windshield-washer reservoir is. Then take a big magic marker and label it for her.
Ray: The next thing I'd do is take the car to a mechanic and have the coolant flushed out and replaced. But I don't think she did any damage.
Tom: Me neither. If I had to guess, I'd say the dominant ingredients in Windex are water and ammonia. There might even be a little ethylene glycol (aka coolant) in there.
Ray: There's a small amount of soap in Windex. But my guess is that any suds would be suppressed by the high pressure inside the cooling system. I mean, she might find her engine compartment overflowing with soap suds tomorrow morning, but I doubt it. It's not like she put Dawn dishwashing liquid in there.
Tom: Flushing the cooling system certainly will remove all doubt about any future damage that might result. And she can feel good knowing she has the cleanest cooling system in the neighborhood.