Mechanics apply with in

If it is a leak from compression escaping from the cylinder, I don't know of anything, nor have I ever seen anything that can fix the problem, even temporarily by adding to the coolant. I have seen products that claim to but never worked. You'd be talkin about easily in excess of 100 PSI and probably more like 150 PSI. That's a lot. Now if it's just leakin coolant from the water jacket side with no compression then I would give it a try.