Last summer while on a trip my Buick LeSabre with...

Dear Car Talk

Dear Car Talk | Aug 01, 1994

Dear Tom and Ray:

Last summer while on a trip, my 1987 Buick LeSabre with 120,000 miles overheated due to the radiator being clogged. Replacement of the radiator solved the problem. I annually drain, flush, and replace the antifreeze, but I can't seem to get the corrosion out of the water fins that you can see inside the radiator. The mechanic who replaced the radiator told me that instead of wasting my money on Quick Flush, I should use a small can or Comet or Ajax cleanser. Just pour the powder into the radiator, run the engine for 20 minutes, drain the system, and flush twice with water before adding new coolant. He assured me that doing this every year would keep the radiator corrosion free. What do you two think??

RAY: I don't know, Michael. Just because the radiator is something you "flush," doesn't mean you should clean it with Comet or Ajax. I don't remember the outside of the Comet bottle saying "cleans toilets, sinks, pots, pans, and cooling systems on '87 Buicks."

TOM: In fact, I wouldn't put ANY cleaner in there, Michael, unless the system has been neglected for years and years. And in those situations, the best thing to use is a cleaner that's basically oxalic acid, with a neutralizer afterflush.

RAY: And besides, I don't think your problem was INSIDE the radiator anyway. I'd bet my brother's salary this week that your radiator rotted from the OUTSIDE. 90% of the bad radiators we see these days are due to corrosion of the external cooling fins, not internal rot.

RAY: And with 120,000 miles, you got your money's worth out of that last radiator. If you drain the system once every year or two and refill it with new coolant, you should never have to resort to a chemical flush. And if you live in the snow belt, make sure you wash the radiator as well as the car during the winter, because road salt is the primary cause of external radiator corrosion.

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