Well, I had some strong vinegar here (I don't know if it was 20% or 30%) and I poured it into the water pump opening. It bubbled, fizzed and reacted for about 8 or 9 hours and then stopped. I drained it off and learned it had dissolved quite a bit of crud in there during that time. Apparently after it reacts with rust, crud, etc it sort of neutralizes itself or loses its punch. I didn't expect that, but maybe that is the nature of it. It certainly seemed to open things up, however. I'm going to order some 30% vinegar from Amazon and run some more into the block (undiluted) and also dilute to about 15% and shake it around in the radiator.
If you're interested, please stay tuned. Sooner or later I'm going to figure out what will work the best.
Jon
