Citric Acid Flush Precipitate

[fraso]

I've done several citric acid flushes on older cast-iron engines and I've noticed that there is a white precipitate that settles out.

Any idea what this white precipitate might be?

 

[Boomer]

If you used hard water, you might be seeing calcium or magnesium citrate salts forming.

 

[fraso]

I would have used filtered water from my pond for the flush water. I was expecting that there were calcium and rust deposits in my engine as previous owners may have used tap water for coolant.