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Pressure Testing Cooling System

  1. With engine off, wipe radiator filler neck seat clean. Fill radiator to correct level. Attach tester to radiator and pump until pressure is at upper level of radiator rating.
  2. If pressure drops, inspect for external leaks. If no leaks are apparent, detach tester and run engine until normal operating temperature is obtained. Reattach tester and observe. If pressure builds up immediately, a possible leak exists from a faulty head gasket or crack in head or block.
    NOTE: Pressure may build up quickly. Release any excess pressure or cooling system damage may result.
  3. If there is no immediate pressure build up, pump tester to within system pressure range (on radiator cap). Vibration of gauge pointer indicates compression or combustion leak into cooling system. Isolate leak by shorted each spark plug wire to cylinder block. Gauge pointer should stop or decrease vibration when leaking cylinder is shorted.