One problem related to coolant leaking has been reported for the 2004 Chevrolet Avalanche. The most recently reported issues are listed below.
Vehicle started experiencing a gradual coolant loss, found out vehicle has a manufactured faulty cylinder head(s) from castech. Will cost $$$$ to repair. Gm will not address the problem except with gm #06-06-01-019b information on gradual coolant loss over time with no evidence of leak found, (June 12, 2007).