cosmomiller

It may behoove you to take a look at Billman's coolant bleed section so you may become acquainted with the perils of having air in the system. If you don't perform the bleed properly, you may think it is fine for a while but have a sudden overheat that can really screw up the engine.

AndrewTheFurst

@cosmomiller I Definately looked that up and will follow his instructions carefully when filling it up and burping the system. My question is more on doing a full coolant flush, rather than just draining the old coolant and refilling it with new coolant.

Car Analogy

Not sure why no one is answering your actual question.

We don't know what the green stuff was. Honda is blue. If it were me, I'd do a flush with distilled to be safe, only because unsure what green was.

We all say change all fluids to set baseline when buying used (even though that applies mostly to lubricants, the baseline concept is all being considered here). How can it be a baseline if you aren't even sure what you mixed with?

I wouldn't obsess over every trace of green though. Just a decent flush so ots mostly clear, then make sure you drain enough that your refill is still enough coolant ratio.

cosmomiller

A true flush with distilled water is time consuming. Any leftover water not drained will dilute the coolant to some degree. As an alternative, you can do a basic Billman drain, replace coolant and drive a short time only to drain again and refill. The resulting coolant will have a very low residual of old coolant to be negligible.

When I replaced my coolant after a decade, I simply followed Billman's procedure and refilled with Honda coolant and that was it.