Step 1: Open the Hood
Locate the hood release lever inside your Elantra. Pull on the lever and lift the hood until the prop rod holds it open.
Step 2: Check the Left Side of the Engine Bay
The thermostat housing is located on the passenger side (Left) of the engine, towards the front. When standing in front of the vehicle, it is located slightly to the left of the center.
Step 3: Locate the Housing
Look for a cylindrical, metal unit with two coolant hoses connected to it. One of the hoses is thicker than the other. This is the thermostat housing.