Radiator Cap 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 (A). Wet the radiator cap seal with engine coolant, then install it on a commercially available pressure tester (B).

Fig 1: Checking Radiator Cap
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Apply a pressure of 93-123 kPa (0.95-1.25 kgf/cm² , 14-18 psi).
Check for a drop in pressure.
If the pressure drops, replace the radiator cap.