The sixth-generation Elantra was introduced in 2015 in South Korea and released for sale in the North American market in 2016 for the 2017 model year. The 2015-2020 Elantra has been sold in SE, Limited Edition, Ultimate Edition, Sport, and Value Edition trim levels.
a leaking gasket, a defective part. You must provide more info regarding the location and any running anomalies. An engine only has ONE block, so I can't even guess where the leak is.