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Home Made Flush?

Q. Thanks for your great articles on cooling systems. I've heard that adding Potassium dichromate crystals, about 1/3 oz. along with TSP (Tri-Sodium Phosphate) or Sodium Carbonate in 4 quart water when flushing the system will not only clean the rust but will inhibit further corrosion.

Home Made Flush?

Have you heard of this and do you know if it's effective?


A. I have to admit that this is a new one on me. I'm sure a lot of old-timers have formulas similar to this that they use to do a certain job and they quite possibly work. One such idea is to add a capful of anti-freeze to the gas tank. The anti-freeze mixes with the water, keeps it from freezing and will burn in the engine. This will, purportedly, will get rid of any water in the tank.

TSP is a chemical found in laundry detergent and has been banned in some states as a pollutant. It can still be found in hardware stores since it is also used as a concrete and brick cleaner. Is it effective in a cooling system? I don't know. It does a good job cleaning my work clothes, but I don't know what it will do for a cooling system.

Personally I would use a good commercial cooling system flush that I know is safe for my cooling system and all the additives I need to protect it are in the anti-freeze I use.

Added 5/29/04

Hi Vince; Saw the question from one of your readers about using a mixture of potassium dichromate and trisodium phosphate in your column. As you told him, TSP is a good laundry cleaner. It would probably work in a cooling system as well.

However, the real reason I decided to write was about the chromate. Dichromate is a very strong oxidizer. It will chew up a lot of organic compounds. That's probably why it works as a cleaner. It was, in fact, used in the cleaning procedure for the ASTM D-2809 water pump test.

It was also used many years ago as a corrosion inhibitor - again because of it's strong oxidizing properties. It has also been used to make so called chromate conversion coatings on metals to protect them from corrosion.

The problem here is that hexavalent chromium, the form present in chromate, is a carcinogen. That is why chromate has been removed from the ASTM cleaning procedure and why it is being removed from a lot of other applications. I would not suggest that your reader use it to flush his cooling system. If he does use it, he needs to be careful to flush it out very thoroughly. It can mess up a modern coolant.

John J. Conville

John Conville was manager of Antifreeze R&D for BASF in the US for about 15 years.

As a bit of trivia, the movie Erin Brockovith was about the resuts of hexavalent chromium contamination.

Additional Information provided courtesy of AllDATA

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