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what to do now?
My question is if my Mercedes Benz Radiator Hose were crossed at the firewall connections could this be the problem or does it matter which direction water flows through the heater core? Upon further checking I have found that the heater hoses are cold when engine is at operating temp. One hose is slightly warm coming out of the block for several inches but cold where it is connected to the heater core and the other hose is cold its entire length. Need some ideas on this cause further checking will require removing the upper intake manifold to access the connections to the heater core. 
