ODI UPGRADED THE PRELIMINARY EVALUATION TO CONDUCT A FULL TECHNICAL ANALYSIS, INCLUDING TESTING.THE TESTING AND ANALYSIS SHOWS THAT A TORN DIAPHRAGM IS A SLOW PROGRESSIVE TYPE OF FAILURE.THE TEAR PROPAGATES IN A SLOW METHODICAL MANNER AND BRAKING PERFORMANCE IS SIMILAR TO AN UNTORN UNIT UNTIL THE TEAR EXCEEDS 1/2 INCH.ODI'S TESTING INDICATES THAT TEARS GREATER THAN 1/2 INCH REQUIRED INCREASED PEDAL EFFORT.HOWEVER, AS THE LENGTH OF THE TEAR INCREASED BEYOND 1/2 INCH, A HISSING SOUND COULD BE HEARD EMITTING INTO THE PASSENGER COMPARTMENT WHERE THE MASTER CYLINDER PLUNGER PASSED THROUGH THE FIREWALL. ODI HAS DETERMINED THAT A SAFETY-RELATED DEFECT TREND HAS NOT BEEN IDENTIFIED AT THIS TIME AND FURTHER USE OF AGENCY RESOURCES DOES NOT APPEAR TO BE WARRANTED.THE CLOSING OF THIS INVESTIGATION DOES NOT CONSTITUTE A FINDING THAT NO SAFETY-RELATED DEFECT EXISTS.THE AGENCY RESERVES THE RIGHT TO TAKE FURTHER ACTION IN THE FUTURE IF WARRANTED BY THE CIRCUMSTANCES.ODI'S COMPLETE TECHNICAL ANALYSIS WITH TEST DATA IS ATTACHED.