The left bolt opening for the thermostat housing is not closed properly and is causing coolant to leak.
I suspect the thermostat seal or thermostat housing has failed. Performing a cooling system pressure test should provide a definitive answer. This test uses dedicated equipment to pressurize the cooling system and pinpoint the leak. I suggest having a professional, such as one from YourMechanic, perform this task for you so that you can get your car safely back on the road.
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