Have an 06 LBZ, 195K now but completely rebuilt w/ arp studs at 175K, never overheated. Getting coolant in the oil but it only happens when its running. Will lose about a quart in 100 miles. Lots of vapor burning off out of crankcase vent tubes and oil fill tube. Oil gets sludgy, but not milky. If I pressurize the cooling system, even when hot it will hold good pressure for days. No white coolant smoke unless it idles for at least 20 minutes and then you get on it. It clears up pretty quick. No coolant will come out of glow plug holes after cooling system has been pressurized. No strange burn patterns on glow plugs to indicate coolant contacting them. EGR cooler is gone so its not getting in there. The coolant stays clean and doesn't appear to have oil in it at all. No seepage from water pump weep hole so doubtful its getting in there. No coolant pressure build up at all when running or hard hoses so head gasket unlikely. I am thinking it has to be entering at a place with no oil pressure such as the water pump or cracked block but why only when running?? I leaning towards pulling the water pump first and if thats good, bite the bullet and pull the motor to get the upper pan off to inspect journals and cylinders but afraid it may be tough to even find then since it only does it when running. Any ideas? Thanks!!