[stepside67]

I have a 2001 Suburban with 213,000 miles with same symptoms and it turned out to be a cracked head. small hairline crack on top side of head around head bolt. This is fairly common... you can google 'Castec heads'. You will need to run a pressure test to confirm this. Other common places that leaks occur on this model include: radiator tanks, quick connect fittings to heater, water pump gasket. On mine I ended up spending the money to fix cracked head and truck is doing fine. Good luck on yours.

Keith