Another suggestion. . . .
pull the rad and have it serviced. There are a few places in SD that do that: got to be some in SF. They can save you a lot of trouble; if it can be de-scaled, they can do it. If not, well that will save you lots of time in wasted effort.
Yes, that green stuff and tap water is bad news!
Regards . . . . JimF
'94 S500 Cpe
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