Please Help Problem after changing coolant
 

Hey, my coolant light has been going on when I started my car for a while now. So, I changed my coolant today and followed all the right steps...plus I have done it before with no problems. I drained all the coolant out and flushed the system with a couple gallons of distilled water. I refilled it with Prestone antifreeze/distilled water mix and took it for a drive. When I came back to check the levels, there was like a yellow mustardy type paste inside the whole tank. I immediately took it to mazda and they said that they have to replace all the hoses,radiator, etc....totalling $3000. I thought that was outrageous. They said it's because I mixed coolants...but I flushed the whole thing and there was green antifreeze in there and I put green back. Does anybody know what happpened and if there is a way to fix it that doesn't cost so much. Any input would be helpfull. Thanks

Check the type of coolant you got against the manual, but I think if you got ethylene glycol based coolant, you should be ok I think. There are more specialty type coolants out there now, so double check.

What strikes me is your first sentence. If you've been driving with low coolant then perhaps there was some portion of the system that was not being protected. This might have allowed some corrosion/rust/scale to accumulate which then got loosened/removed when you finally filled the system with fresh coolant. Just a thought. Rinse, Repeat.