Look at the see-through coolant resevoir tank. The coolant level is satisfactory if it is between the "FULL" and "LOW" lines on the tank. If the level is low, add coolant of the same type as already in the system.
The coolant level in the resevoir tank will vary with engine temperature. However, if the level is on or below the "LOW" line, add coolant. Bring the level up to the "FULL" line.
Always use the same type of coolant as already in the cooling system. For information on coolant, see Changing the Engine Coolant.
If the coolant level drops within a short time after replenishing, there may be a leak in the system. Visually check the radiator, hoses, radiator cap, drain plug and water pump.
If no leak can be found, have the cap pressure tested at your Toyota dealer.

CAUTION: To prevent burning yourself, do not remove the radiator cap when the engine is hot.