2013 Chevy Impala LT with around 130k miles. Everything has been running great but the other night I noticed smoke coming out of the hood and I immediately pulled over and noticed my coolant was low. At home I poured in nearly a full gallon and noticed a major drip. Any idea on what part this would be and how serious? I also put a photo of what the spray looked like after I pulled over. Many thanks in advance.