LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2001 >> Prius >> Repair and Diagnosis >> Engine Mechanical >> Cooling System (Mechanical) >> Radiator And CONDENSOR Module >> On-Vehicle Inspection
April 5, 2026: LEMON Manuals is launched! Read the announcement.

On-Vehicle Inspection

    WARNING: To avoid the danger of being burned, do not remove the radiator cap while the engine and radiator are still hot, as fluid and steam can be blown out under pressure.
  1. Remove Radiator Cap  .
  2. NOTE:
    • If the radiator cap has contaminations, always rinse it with water.
    • Before using a radiator cap tester, wet the relief valve and pressure valve with engine coolant or water.
    • When performing steps (a) and ( b) below, keep the radiator cap tester at an angle of over 30° above the horizontal.
    NOTE: Use the tester's maximum reading as the opening pressure. If the opening pressure is less than minimum, replace the radiator cap.
  3. Inspect Radiator Cap 
      NOTE: Push the pump at a constant speed.
      Fig 1: Installing Radiator Cap Tester
      G02810822Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Using a radiator cap tester, slowly pump the tester and check that air is coming from the vacuum valve.

      Pump speed: 1 push/(3 seconds or more) 

      If air is not coming from the vacuum valve, replace the radiator cap.

    2. NOTE: This pump speed is for the first pump only (in order to close the vacuum value). After this, the pump speed can be reduced.
    3. Pump the tester and measure the relief valve opening pressure.

      Pump speed: 1 push within 1 seconds 

    Standard opening pressure: 

    74 - 103 kPa (0.75 - 1.05 kgf.cm 2  , 10.7 - 14.9 psi) 

    Minimum opening pressure: 

    79 kPa (0.8 kgf.cm 2  , 11.5 psi) 

  4. Inspect Cooling System For Leaks 
    Fig 2: Inspecting Cooling System For Leaks
    G02810823Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Fill the radiator with coolant and attach a radiator cap tester.
    2. Warm up the engine.
    3. Pump it to 118 kPa (1.2 kgf.cm2 , 17.1 psi), and check that the pressure drops.

    If the pressure drops, check the hoses, radiator or water pump for leaks. If no external leaks are found, check the heater core, cylinder block and head.

  5. Reinstall Radiator Cap