Thank you George, I contacted the repair shop and told them I would like them to drain the system and refill it with distilled water and coolant. He said they have always used the tap water and never had a complaint. I explained that the other customers were probably not into cooling system repairs over $20,000 in the last 5 years either. I also went to the Indio Water Authority website and read a comment on there that the Coachella Valley ground water was hard and contained mainly calcium and magnesium. He then agreed to drain the system and refill with distilled water.
Larry Fisk