Originally Posted by JohnR
I'm assuming that this is bad, right?
Check your hoses and the like. see if you can pinpoint the leak. it is probably just a hose. When you flushed it, did you insert the T fitting? or did you just shove the garden hose into the coolant line? You most likely didn't flush out the heater core but you probably flushed out the engine block.
you need to know what the leak is before you can progress.