Radiator Cap
WARNING: This page is about a different car, the 1988 Toyota Celica and 1987 Toyota Celica. However, it is still accessible from the selected car via links, so may be relevant.
Visually inspect radiator cap, then dip cap in water and connect to tester. Pump tester to bring pressure to upper limit of cap specifications. If cap fails to hold pressure within specifications, replace cap.