Two problems related to radiator have been reported for the 2015 Chevrolet Sonic. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2015 Chevrolet Sonic based on all problems reported for the 2015 Sonic.
1st at 20k miles (2019) my car wouldn't start, stuck late night. Called aaa, battery had dead cell so I purchased one for $200. Months later found out it was covered under the warranty. I started smelling coolant (2019). Dealer said it was the water pump. It was covered under warranty. Started smelling coolant again (2019), it was a valve, wasn't covered. The car wouldn't start, dead cell in the battery again (2020) started smelling coolant (2020), needed a new radiator, wasn't covered under warranty. Started smelling fumes & had a leak. It was the purge solenoid needed replacing, another $500. Two months ago (Nov 2020) the ambient sensor went out $450. Now today (Jan 5, 2021) the airbag light is on and I'm told it's the internal sdm fault and will be close to a $900 repair.
Car is less than 3 years old and the radiator is rusted/corroded. This kind of corrosion should not happen on a car less than 3 years old. I kept smelling something burning when driving on the highway, so I started monitoring the coolant levels. I was adding more than a gallon of coolant each month.