NHTSA Preliminary Evaluation PE14027

The Office of Defects Investigation (ODI) opened PE14-027 based on a report of 13 front brake hose (jounce hose) failures in 11 vehicles in the District of Columbia Metropolitan Police Department (DCMPD) fleet of 46 model year (MY) 2013 Ford Explorer Police Interceptor (PI) vehicles (VOQ 10621634).The DCMPD fleet provided Ford with 71 jounce hoses for analysis, including 4 of the 13 failed hoses.Inspection of each of the failed hoses identified a small tear in the outer cover on the body end of the hoses on the outboard side. Ford?s lab analysis of these hoses identified splits in the inner liners 1.5-2.0mm from the end of the nipple (outside of the crimped ferrule joint).Ford conducted pressure testing of 10 randomly selected samples of the remaining 67 hoses that had not experienced leaks and 9 of the samples leaked at 6,000 psi.Ford?s examination of the 9 hoses that leaked in the pressure tests found 4 that failed on the outboard side of the hose (similar to the 4 leaking field parts) and 5 that failed on the body end of the hose on the inboard side.Four additional non-leaking hoses were sent to the hose supplier, Hitachi, for analysis.Broken yarn was observed in scanning electron microscope examinations at both the body side and caliper side hose to ferrule crimps, indicating severe bending stress had occurred at these locations. Hitachi supplied an additional set of non-leaking field return hoses and a brand new set of hoses to an outside laboratory (Element Materials Technology) for analysis.The lab did not identify any manufacturing or material deficiencies in the hoses and concluded that the hose failures were caused by excessive bending stresses.Based on the examinations of the returned jounce hoses, Ford conducted durability testing on new hoses that were the same design as those found on the subject vehicles.Ford first determined the worst case conditions for the hoses; jounce bumpers removed, internal rebound stops fully compressed, and shock absorbers a