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Home >> Ford >> 1989 >> Bronco II RWD, Standard, M5OD-R1 >> Repair and Diagnosis >> Engine Mechanical >> Cooling System (Mechanical) >> Cooling System Specifications >> Testing >> Pressure Testing >> Cooling System
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Cooling System

  1. With engine off, wipe radiator filler neck seat clean. Radiator coolant level should be one inch (25 mm) below filler neck before testing. Wet rubber seal of radiator cap and install tightly on radiator.
  2. Remove coolant temperature sending unit from engine and install adapter fitting from Cooling System Pressurization Kit (021-00012). On Vans, remove radiator overflow hose from retainer clips. If vehicle is equipped with an expansion bottle, use separate hose.
    NOTE: Pressure may build up quickly. Release any excess pressure or cooling system damage may result.
  3. On other models, remove radiator overflow hose from overflow nipple. On all models, insert free end of overflow hose into a container of water. Attach pressure pump into adapter fitting and pressurize cooling system to about 10 psi (.70 kg/cm2 ).
  4. No bubbles should be present in water container at this time. If okay, increase system pressure gradually until a slight stream of bubbles appear in water container. This indicates release pressure of radiator cap. If radiator cap does not release after applying 16 psi (1.13 kg/cm2 ) of pressure, replace cap.
  5. If radiator cap does not hold pressure, remove and wash cap in clean water. Check sealing surfaces in cap and radiator filler neck. Inspect cam lock flanges for maximum engagement. Pressurize cooling system again. Repeat step 4). Replace radiator cap if it still does not hold pressure.
  6. With a working radiator cap, pressurize cooling system and observe pressure gauge reading for 2 minutes. On Aerostar, Bronco II and Ranger, pressure should hold between 12-16 psi (.84-1.13 kg/cm2 ). On "E" and "F" series, pressure should hold between 10-13 psi (.70-.91 kg/cm2 ). Pressure should not drop during test.
  7. If pressure drops, inspect for external leaks. If no leaks are apparent, remove tester and run engine until normal operating temperature is reached. Reinstall tester and observe. If after pumping tester, pressure builds up immediately, a possible leak exists from a faulty head gasket or crack in cylinder head or block.
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