Radiator Test

WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.

Wait until the engine is cool, then carefully remove the radiator cap, and fill the radiator with engine coolant to the base of the filler neck.
Attach a commercially available pressure tester (A) to the radiator, and apply a pressure of 93-123 kPa (0.95-1.25 kgf/cm² , 14-18 psi).

Fig 1: Applying Pressure To Radiator
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Inspect for engine coolant leaks and a drop in pressure.
Remove the tester, and reinstall the radiator cap.