Move the selector lever to the "P" ("Park") position (automatic transmission) or the gearshift lever to the neutral position and apply the parking brake. If the air conditioner is on, turn it off.
If coolant is leaking from under the vehicle or steam is coming from under the hood, turn off the engine. Do not open the hood until coolant stops leaking from under the vehicle or steam stops coming from under the hood. If there is no visible coolant or steam leak, leave the engine running and make sure the radiator fan is running. If it is not running, turn off the engine.
Check for the presence of the coolant pump drive belt. If it is in place, check its tension. If the belt is OK, check for coolant leaks from the radiator, cooling system hoses, or from under the car. (If the air conditioner was on, cold water will drain from it after the car is stopped; this is normal.).
If the drive belt or coolant pump is faulty or there is a coolant leak, turn off the engine immediately.
If the cause of overheating is not found, wait until the engine coolant temperature returns to normal. If there is a coolant leak, carefully remove the radiator cap and add coolant to the middle mark in the expansion tank.
Caution! A significant decrease in the coolant level indicates a leak in the cooling system.