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I would like to derust the interior water jacket of an antique auto engine

I am restoring a 1931 AA FORD truck. The engine has already been rebuilt a few years ago . Before installing the engine I noticed a lot rust scale a chips in the engine. Apparently the engine builder did not boil out the block. I would like to know if there is a mild acid I could pour into the block to dissolve the rust and scale, such as muriatic acid ⇦this on eBay or Amazon [affil links] , citric or another acid which will attack the ferrous material but will not affect the copper head gasket. Thank you.

Bill Wirth
hobbyist - Stratford, Connecticut, USA
2005

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I did what you are suggesting once and it didn't seem to do any damage to the engine, I drained the cooling system(the car had been sitting for a number of years), filled it with water and let it run for awhile and then slowly added muriatic acid until I lost my nerve. I let the engine run for a while, drained and flushed the system again, and then filled it very quickly with anti-freeze. The cooling system absolutely cannot have anything that is aluminum(like water pump or intake manifold). Like I said, someone's gonna answer this and say how stupid it was to do, but there didn't seem to be any damage to the engine, however I didn't take it apart and inspect it afterward, I just had my fingers crossed. There was positive rust removal based on the color of the water when I drained it afterwards, and I did drive the car for a number of years after that with out problem.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2005