Well my DD crewcab (98 K3500 with 454) has been sporadically overheating and I thought it was a stuck thermostat so today I was going to replace it. I took radiator cap off and saw that it was low on coolant, so obviously thats why it was overheating. I topped it off and it ended up taking a gallon and a half of water. That is alot of damn coolant to leak over a fairly shorty period of time, and I have never noticed any leaks underneath. It does however, have water dripping out of the exhaust. I never thought much of it and kinda figured it was from condensation or something, since the water is clear and my exhaust doesnt "smoke." Could I have a bad head gasket or cracked head?