So I'm working on a 01 lb7 with 320,000 miles on it, it needs injectors again has smoke at idle, exhaust smells like fuel, injector balance rates were within spec but not by much so return rates must be bad, but anyway during disassembly I got one side valve cover off and found the bottom side of the valve cover covered in milky grey sludge and all the rocker arms had moisture on them, the coolant was maybe half gallon low before I drained it, so I drained oil and its all milky but still only drained out about 2.5 gallons so it's not a huge leak, so I have coolant getting in the oil somehow, truck did not have any signs of head gasket failure, no hard rad hose after sitting and no pressure in res, ran fine just had the injector haze. One thing I thought of was the water pump is original could that be it? If I remember right isn't there a weep hole on the back side of the pump as well? Or thought maybe oil cooler but I've never seen a duramax have a oil cooler failure? Any ideas? By the way truck is bone stock