Hey there, could someone in the know help me, please. I've an 02 blzr 2wd,200k+,it started overheating on a very cold day, I only had water in the road, no coolant, water pump seep hole was leaking, I replaced it, all good, so I then replaced heater core, to fix heat, all good, but few days later I overheat again.now waters spewing from water pump area and the water or coolant I had put in is black like oils in it, but it. Don't look as if there's any on my oil dstick.do I have an oil cooler on mine or does this sound like something else?any help please, thanks

 

check your lower intake manifold gasket and thermostate

 

If it has a 4.3L, it has an oil cooler. It is possible for the oil cooler to leak oil into the coolant. Oil pressure is far greater than cooling system pressure, so if the cooler is leaking in the radiator, oil will get into the coolant. It will also increase the cooling system pressure and most likely blow out gaskets, hoses, etc. If that's the case, it needs a new radiator.