Demineralized vs distilled water in radiator - problems?

[labsy]

Hi,

as I am still gathering $$$ for engine repair (coolant leaking on head gasket + chains replacement = 2k EUR) it became a habit to have sometimes more water with me than gas During winter I had to add approx. 1 qt every 200-300 miles as dripping was more like a personal waterfall.

Then I found very cheap DEMINERALIZED water (60 cents for 5 qt) in our local supermarket, and I begun using this one instead of more expensive DISTILLED water. (NOTE: Demineralized water is produced by adding chemicals, which make minerals and hard particles to collect on the bottom, so there are some leftovers of those chemicals for sure. While distilled water is pure vapor distillation, no chemicals added)

Then came the Spring and Summer.

Now, here comes the weird part: Coolant is not leaking anymore.

I am asking myself, whether that's the consequence of:
- either Summer temperatures
- or rust and residues, produced by chemicals of demineralized water (...as I noticed radiator inside at filling cap is covered with thin layer of brown something....looks like rust. And I can tell for sure it was NOT there before)

So I just wanted to do a CLEANING of cooling system with Coolant Flush & Clean...but now I am not sure anymore whether it is a good idea. I might remove garbage which sealed the leaking gasket, rendering leak even worse than before.

What do you say?

[smj999smj]

Either demineralized or distilled water in the cooling system is fine as long as it is mixed 50/50 with the proper type anti-freeze for your vehicle. You don't want to run either alone, without anti-freeze, because that will cause corrosion inside the engine. As far as to whether to flush or not, I can't help you on that one. You have to make that call.

[disallow]

My experience with any kind of rad flush or cleaner is BAD. Don't do it.

Do replace your coolant just as SMJ said, and do make sure to run coolant mixture and not water.

As to why, let's just say you'll probably never stop chasing leaks.

[labsy]

I was leaning towards NOT using coolant flush, but until now I was not quite sure. Will do as you both say, as it also sounds to me like a best option.