It also has a this smell
My car has 1860000 miles.
My car's transmission is unknown to me.
You will need to have the engine tested to see if the head gasket is blown and allowing engine compression to get into the cooling system and forcing coolant out of the reservoir. A mechanic like one from YourMechanic can do the tests for you to see if the head gaskets are blown or you have another issue causing the fluid to be pushed out.
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