Need to solve rust in coolant problem. Had the system flushed but rust persists. Should I flush again or is there an effective treatment?

 

Prestone (I think) makes a 2 part flush... it is oxacylic acid in part 1 and a neutralizer in part two.... comes in a yellow can. Use exactly as indicated. (I also use the prestone flush and fill kit for rinse out) Then go to Prestone Anti-freeze... yea, glycol is glycol but their anti-corrosion addatives are worth the money. That should get all the loose corrosion out and keep new from forming. GL