New and Rebuilt Brake Cylinder Survey and Performance Evaluation

摘要

The Department of Transportation/The National Highway Traffic Safety Administration was concerned that some automotive brake master cylinder rebuilders may introduce burrs or other contamination in their efforts to remove corrosion and/or pitting from the used master cylinder cores. A market survey was conducted to determine the production volume of the various automotive brake master cylinder rebuilders and the most popular models currently in use. A purchase plan for 274 rebuilt master cylinders, based on this information, was formulated. The plan also included 126 units from Original Equipment Manufacturer's (OEM) and After-market Manufacturer's resulting in a total of 400 units. The units were tested in accordance with test procedure SAE J1153. Test results were analyzed for compliance with the performance requirements of SAE J1154 and applicable manufacturer's specifications. The analysis was used to establish performance categories. These categories were used to make performance comparisons between OEM, After-market and Rebuilt groups as well as the various manufacturer's groups. A post-test inspection was conducted in an effort to determine failure causes. The high number of unit failures which occurred during testing appeared to indicate certain test conditions to be too severe. Piston seal damage was found prevalent in a high number of master cylinder falures. Some correlation between the high temperature durability test and failures due to seal damage was established. The OEM units, as a group, demonstrated the lowest failure rate followed by the After-market and Rebild units respectively. Cylinder bore measurements taken after testing indicated that some of the Rebuilders may be removing excessive amounts of metal during bore reconditioning.