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Home >> Ford >> 2003 >> Explorer 4.0 K, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 249 (Engine Cooling System) >> Diagnosis And Testing >> Engine Cooling >> Component Tests >> Pressure Test
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Pressure Test

WARNING: This page is about a different car, the 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn the engine OFF.
    2. WARNING: To avoid personal injury, do not unscrew the coolant pressure relief cap while the engine is operating or hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly.
  2. Check the engine coolant level. Refer to COOLING SYSTEM DRAINING, FILLING AND BLEEDING .
  3. Connect the Radiator Heater Core Pressure Tester to the degas bottle nipple and overflow hose. Install a pressure test pump to the quick-connect fitting of the test adapter.
    4. NOTE: If the plunger of the pump is depressed too fast, an erroneous pressure reading will result.
  4. Slowly depress the plunger of the pressure test pump until the pressure gauge reading stops increasing and note the highest pressure reading obtained.
  5. If the pressure relief cap does not hold pressure, remove and wash the pressure relief cap in clean water to dislodge all foreign particles from the gaskets. Check the sealing surface in the filler neck.
  6. If 8-9 kPa (13 psi) cannot be reached, install a new pressure relief cap. If more than 12 kPa (18 psi) shows on gauge, install a new pressure relief cap.
    7. CAUTION: If the pressure drops, check for leaks at the engine-to-heater core hoses, engine-to-radiator hoses, water valve hose (if applicable), oil cooler return tube gasket, radiator, and heater core, or other system components and connections. Any leaks which are found must be corrected and the system rechecked.
  7. Pressurize the engine cooling system as described above (using a pressure relief cap that operates within the specified upper and lower pressure limits). Observe the gauge reading for approximately two minutes. Pressure should not drop during this time.
  8. Release the system pressure by loosening the pressure relief cap. Check the engine coolant level and replenish, if necessary, with the correct engine coolant mixture. For additional information, refer to COOLING SYSTEM DRAINING, FILLING AND BLEEDING .
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