NHTSA Preliminary Evaluation PE06041

THIS INVESTIGATION WAS OPENED BASED ON ODI'S RECEIPT OFEWR INFORMATION PERTAINING TO COLLAPSING BRAKE VACUUM HOSES ON THE SUBJECT VEHICLES.THE VEHICLES OF CONCERN ARE MEDIUM DUTY TRUCKS, MODEL YEARS 2006 - 2007,MODELS FE84D, FE85D AND FG84D.ODI MET WITH MITSUBISHI OFFICIALS AND DROVE A TRUCK WITH THE COLLAPSED HOSE.IT WAS DETERMINED THAT THE VACUUM BRAKE BOOSTER HOSE CAN FLATTEN OR COLLAPSE WHILE THE TRUCK IS BEING DRIVEN, RESULTING INDEGRADATION (REDUCED VACUUM) OF THE BRAKE POWER-ASSIST SYSTEM. THE REDUCTION IN AVAILABLE ENGINE VACUUM TO THE BRAKE BOOSTER REQUIRES THE DRIVER TO APPLY INCREASED BRAKE PEDAL PRESSURE TO ACHIEVE THE EXPECTED STOPPING DISTANCE. DURING THE INVESTIGATION, ODI LEARNED THAT THE BRAKE VACUUM HOSE WAS MANUFACTURED WITH INSUFFICIENT WALL THICKNESS, ALLOWING THE HOSE TO COLLAPSE DURING NORMAL VEHICLE OPERATION. DURING THE RECALL MITSUBISHI WILL REPLACE ALL VACUUM BRAKE BOOSTER HOSES ON THE APPLICABLE TRUCKS.THIS INVESTIGATION IS CLOSED.