I've got a 1991 school bus with a CAT 3116 that gets a little hot on the highway and the stop engine light comes on. Only the top 25% of the radiator gets hot while the bottom remains very cold.

I've read about people using bleach, vinegar, and citric acid, among other things to clean their radiators, but some of these seem very harmful to the engine and cooling system.

  1. Has anyone used sulfamic acid to clean out a radiator?
  2. What are the pros/cons of using sulfamic acid for this purpose?

My radiator is steel, about 30" x 30" x 4".

1 Answer 1


Probably. Sulfamic acid is the material of choice to clean industrial tube heat exchangers. These units are steel and brass. I can't say if it is good with aluminum as aluminum is almost never used in refinery heat exchangers. I doubt your radiator is steel, I have never seen a steel auto radiator. Today they are generally aluminum . Older ones were copper fins with brass ends or tops. Sulfamic is good in a cast iron block and limited time in an aluminum block should be acceptable ( not as bad as vinegar or citric ).A caution is that some engines may use a few small fittings of aluminum or zinc in a a system that is otherwise all steel/iron and copper. Look at fittings like hose connections.

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