proheat gen 4 problems

Is the water flowing threw the engine? Did you use a garden hose both ways and flush the anti freeze out of the whole engine when the radiator hoses were off the engine and the water pump and thermostat was out a motor to make sure the water was flowing both ways threw the engine?
(Water jacket could be blocked in the engine)

Did you do a compression test on the engine?
Any bubbles coming out of the antifreeze and is the antifreeze disappearing from the engine?
Is there sweet smell of antifreeze coming out of the APU exhaust system?
(Could be water heating going threw the cylinders and heating up the water jacket)

Is the oil pump working and oil pressure correct with the correct engine oil?
(May not be getting any or very little lubrication)