Thanks Zed, last night I ran the garden hose and performed this - looking at the service manual, I couldn't find any mention of a bleed bolt or similar. I left the engine-side/thermostat-side hose on, and ran water through the passages with the garden hose. When doing this, water did successfully run through and come out the top of the water pump (see images below).Spraying a garden hose couldn’t hurt. Try it and see what and where it comes out.
The internal coolant passages and water jackets, I believe, are large enough that the stop leak won’t bother them but you got to get any remaining stop leak out to reduce the risk of clogging the radiator in the future.
Youll be ok.
Also, while garden hosing, there’s usually a bolt somewhere in the system meant for bleeding air out of the system while filling. Flush that out too. And the thermostat if it’s not too much trouble.
I ran about 2 to 2.5 gallons through it in this manner over a course of ~15 minutes. Everything that came out was - totally clear. No chunks or anything like that. (see picture). A couple specks of dirt but not much at all. I was not able to get great pressure through it, as I couldn't seal the garden hose to coolant hose connection, but the coolant hose effectively made a column of water that then went through. I did not take the thermostat off - but, the water went through the thermostat, yeah?
So - I think this is good news?
Also, I had to use my drain pan again to catch the water; I tried to cut you a nice slice of the tofu pie Zed for scientific purposes, but couldn't get it out cleanly. I put a bunch of what I could get out in a dish which we'll save for monitoring.
Water after flushing through passages:
Tofu pie - this is after 8-9 days of sitting in the garage: