my Sierra 5.3 had headgaskets put on it a few months ago, the guy never said why. now its running a slight bit rough and I notice excessive amounts of liquid and steam out of the exhaust. truck has cats too. its throwing code p0118 something about coolant temp when I just replaced the seemingly bad ECTS. do you guys think Ive got a craked head? whats a good way to test and diagnose this? So far I see no milky substance in the oil but Ive only put about 60 miles on the truck.

 

pressure test the system