On-Vehicle Inspection

WARNING: This page is about a different car, the 2004 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

CHECK COOLING SYSTEM FOR LEAKS
CAUTION: Do not remove the radiator cap while the engine and radiator are still hot. Pressurized, hot engine coolant and steam may be released and cause serious burns.
1. Fill the radiator with coolant and attach a radiator cap tester.
2. Warm up the engine.
3. Using the radiator cap tester, increase the pressure inside the radiator to 137 kPa (1.4 kgf/cm² , 19.9 psi), and check that the pressure does not drop.
  
  Fig 1: Identifying Checking Cooling System For Leaks
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  If the pressure drops, check the hoses, radiator and water pump for leaks. If no external leaks are found, check the heater core, cylinder block and head.
CHECK ENGINE COOLANT LEVEL AT RESERVOIR
1. Check that the engine coolant level is between the LOW and FULL lines when the engine is cold.
  If the engine coolant is low, check for leaks and add "Toyota Super Long Life Coolant" to the FULL line. If "Toyota Super Long Life Coolant" is not available, use a similar high quality ethylene glycol based non-silicate, non-amino, non-nitrite and non-borate coolant with long-life hybrid organic acid technology. Do not substitute plain water for engine coolant.
CHECK ENGINE COOLANT QUALITY
1. Remove the radiator cap.
  CAUTION: Do not remove the radiator cap while the engine and radiator are still hot. Pressurized, hot engine coolant and steam may be released and caused and cause serious burns.
2. Check if there are any excessive deposits of rust or scale around the radiator cap and radiator filler hole, Also, the coolant should be free from oil.
  HINT:
  
  If excessively dirty, clean the coolant passage and replace the coolant.
3. Reinstall the radiator cap.