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Q: Coolant issue engine overheating don't know cause

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Passenger floor wet. Overheating when driving. No leaking under car.steam coming out vents,smell coolant from vents. Adding water daily. Electrical fan by radiator do turn on. My Ac fan currently doesn't work.im thinking it's heater core. Took of radiator cap when cooled off and noticed black like dirt around the cap on the metal part.

My car has 190000 miles.
My car has an automatic transmission.

Hello. You are most likely correct on the heater core being your issue. This is the component that is located closest to the firewall which will have coolant running to it. The heater core also holds quite a bit of fluid, and would be able to saturate the passenger floorboard if it cracked. Otherwise you would see a leak on the outside of the vehicle more so than inside. You are going to have to drain the coolant to make the repair to the heater core anyway, so do not worry about the gritty coolant at this point. Old coolant can get that way, and you will be flushing the system anyway. Start by diagnosing the extent of damage to the heater core, and most likely replacing it. Then flush the entire cooling system and refill with fresh coolant. Pressure test the system to verify the repair.

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