^ I ran the soda crystals in the Gemini back when we used to live in the same street Bart. I think I ran them in the car for a week, then dumped bottom hose, rinse/repeat and It ran clear.
The Gloria just had 45min of back flushing when I got that (whilst running, dumping straight into the farmers paddock) - and it'd been parked for 15 odd years or whatever it was. Then it ran clean, however ultimately the Water pump impellor was rusted away & radiator still needed rodding out.
I would just about put the shitty one back in and run it up to temp/cycle a few times with above concoctions then dump/back flush?