Heater core hose connections could be cracked or loose. It is doubtful; however, should be looked into that the heater core itself is leaking. There should be a plenium in the engine bay on the firewall housing the heater core. Remove it and replace the hoses if they are cracked, hard or brittle. Drain the heater core and submerge in the sink (not letting water get into the heater core) and check for air bubbles. (don't be confused by air bubbles trapped in the fins as the heater core will fill with water if there is a leak)

Answered by airsoftsoldrecn9
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