The citric acid is a concentrated powder. It basically eats the scale and corrosion inside the cooling system. I have always had an inherent concern about anything that eats metal. There are a lot of products out there that will get the job done. If your radiator is less than efficient, I would get it looked at by a pro. If it's bad, a flush will not do the trick..

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Jeff L
1987 300e
1989 300e
1987 BMW 325