The hoses staying hard is normal. With the engine running, warmed up, and the heater on high, feel both heater core hoses. Both should be hot. If they are, check and repair the blend air door located near the heater core. If only one is hot, check for air blocks. Try to bleed coolant through the heater core. I usually loosen the return line.
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Sunday, February 12th, 2012 AT 9:09 PM