The heater will usually blow cold during low coolant conditions, primarily at idle when the flow is lowest from the pump. If you notice coolant from the block, geographically what position? Center front would suggest a pump, but it could also be intake gasket, thermostat housing, or hose. On the sides of the block, could be freeze plug. Have the system pressure tested. An inspection under pressure should reveal a leak. This can also be a thermal leak, where it may leak cold, but not warm, or vice versa.
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Friday, December 9th, 2011 AT 4:12 AM