Vinegar is far more acidic than the citric acid .

Do it correctly and you don't have to worry, I hear your concern about damaging the water core but if any leaks appear, it's because that part was already bad and only the rust crud or solder bloom was keeping the coolant in .

As far as no hear, push the defroster button, this will by pass the entire system and give you max heat to the windshield .

If you get a blast of cool defroster air I'm betting your heater core is plugged, that's very, *VERY* common .'

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better