Crankshaft Pulley on a 1999 Nissan Altima


#1

Will it break and cause oil to leak form the car.


#2

It could happen but the chances of that are pretty slim.
I used to work for Nissan and I remember a truck that came in with a broken pulley. The part of the pulley with the chunk missing chewed up the front crankshaft seal, which led to rapid oil loss, which then led to the truck owner continuing to drive with the oil light glowing.
The final step was an engine trashing.

Much depends on where the pulley could crack. Any particular reason for asking this? It would be a very rare thing to happen.