Inspection After Removal

WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

Check valve seating condition at ordinary room temperatures. It should seat tightly.
Check valve opening temperature and maximum valve lift.

Fig 1: Thermostat Specifications Table
Courtesy of NISSAN MOTOR CO., U.S.A.
Then check if valve closes at 5°C (9°F) below valve opening temperature.

Fig 2: Immersing Thermostat Valves Fully In Container Filled With Water
Courtesy of NISSAN MOTOR CO., U.S.A.