what could cause a water housing unit to crack on a 2001 chrysler sebering 2.7 L

i was driving nd i heard a pop like the tire had blew so i pulled over to check and the tail pipe was smoking and it was leaking antifreeze so i popped the hood and noticed that the water housing unit was cracked. It woundlnt start so i replaced the battery and now it starts but the engine is jumping and its ticking like something is loose on the motor. also its still smoking but not as much as before and the smoke smells like dry gas.