This is my first 6.0L so I was wondering if around the 2001 time frame if these engines develop known problems related to coolant problems, I'm thinking cracked heads, head gaskets... It has almost 300K on the clock and runs great, it just seems that the low coolant light is coming on more often now. No signs of coolant in the oil, no pressure (crankcase pressure) in the cooling system, and no visible leaks anywhere in the engine compartment or around the rear heating/air area. Looking for suggestions.