uhoh- major problem? cracked block?

[MDM]

as always, start simple. You are on the right track so far. Flush the system, check to see that your h20 pump and bearings are in good condition, check that your fan clutch is not leaking, refill with 70/30 water/antifreeze and add water wetter if you like, check all your hoses for cracks or leaks and remember that the way they look on the outside may not be the way they look on the inside. Add a new stat while you are in there- HP180 degree from Edelbrock is accurate and has a large mouth for improved flow. This will establish a baseline to work from and will enable you to diagnose from a known set of values.