Its a risky proposition...See Franks last post...If it just started weeping you might get a 100 miles out of it or 10 feet...Cant predict how long it will hold up.Sorry...
Anything can happen. Wiggle the fan an if no or very little play RUN IT. Do keep a eye on it an listen for noise. Before I would add water, use washer fluid or old anti-freeze. Good Luck you be okay, I ve run them leaking for many a payday
it's not the stuck threads that will bite you. it will be the bolts that went through the water jacket and have almost rusted away...