NHTSA Engineering Analysis EA08009

ANALYSIS OF COMPLAINTS TO ODI AND MERCEDES AND WARRANTY CLAIM DATA SUBMITTED BY MERCEDES INDICATES THAT THE ALLEGED DEFECT HAS OCCURRED AT A LOW RATE (36.5 COMPLAINTS PER 100,000 VEHICLES AND 0.29 PERCENT WARRANTY CLAIM RATE), WITH NO DISCERNABLE DEFECT TREND INDICATING THAT THE RATE OF CHAFING RELATED BRAKE LINE FAILURES IS INCREASING.THERE HAVE BEEN NO NEW COMPLAINTS SINCE JANUARY 2009.WHEN THE ANALYSIS IS LIMITED TO INCIDENTS OF BRAKE LINE LEAKAGE THAT RESULTED IN ALLEGATIONS OF REDUCED BRAKE EFFECTIVENESS, THE RATE DROPS EVEN FURTHER (22.3 COMPLAINTS PER 100,000 VEHICLES AND 0.04 PERCENT WARRANTY CLAIM RATE). MERCEDES PROVIDED DATA SHOWING THAT IN THE RARE INSTANCES WHEN CHAFING DID PROGRESS TO BRAKE LINE LEAKAGE THE DRIVER WOULD BE IMMEDIATELY ALERTED TO A PROBLEM BY ILLUMINATION OF THE BRIGHT YELLOW ESP/BAS WARNING LAMP AND CHANGES IN BRAKE PEDAL FEEL.CONTINUED OPERATION WITH A LEAKING BRAKE LINE WOULD RESULT IN ILLUMINATION OF THE BRIGHT RED BRAKE WARNING LAMP AND AN AUDIBLE CHIME DUE TO LOW MASTER CYLINDER RESERVOIR LEVEL. CONTINUED OPERATION WITH THE BRAKE WARNING LAMP ILLUMINATED WOULD ULTIMATELY DRAIN THE RESERVOIR FOR THE AFFECTED CIRCUIT, RESULTING IN LOSS OF THE CIRCUIT AND AN APPROXIMATELY 80% INCREASE IN STOPPING DISTANCES. SURVEYS CONDUCTED BY ODI AND VRTC INDICATE THAT ROUTING ANOMALIES MAY BE MORE COMMON THAN THE COMPLAINT AND WARRANTY DATA SUGGEST FOR THE SUBJECT LINE BUNDLE, WITH LINE CONTACT OR OTHER ROUTING ANOMALY NOTED IN 13 OF 51 VEHICLES SURVEYED BY ODI AND VRTC (25.5%).WHILE EVIDENCE OF CONTACT BETWEEN THE FUEL LINE AND SUBJECT BRAKE IN A PARTICULAR VEHICLE IS NOT NECESSARILY PREDICTIVE OF EVENTUAL LINE FAILURE/LEAKAGE, SIGNIFICANT CHAFING WEAR WAS NOTED IN TWO SURVEY VEHICLES (3.9%).TO ADDRESS CONCERNS WITH LINE ROUTING AND ENSURE THAT LINES WITH EVIDENT CHAFING DO NOT PROGRESS TO A LEAK CONDITION, MERCEDES WILL CONDUCT AN OWNER NOTIFICATION PROGRAM INSTRUCTING OWNERS TO BRING THE VEHICLES TO A DEALER FOR A FREE INSPECTION AND REPAIR.LIN