Bought a used yaris, now to get it back into shape, need some feedback. [LONG POST]

[johnwk]

Sorry to hear that your new Yaris came with some surprises, but I'm glad your approach is to fix them yourself!

I've used Prestone Flush+Cleaner, because I bought my Yaris with high mileage and no evidence that the coolant had ever been flushed. 4,000 miles later, everything's working normally—no temperature issues or leaks. Most people I've talked to about it said it was probably unnecessary, but your situation may be different given the green coolant.