AIR BRAKES - GENERAL INFORMATIONPRELIMINARY CHECKSNOTE - Before conducting the Pressure Balance,Pressure Build-up Rate, and the Torque Balance Tests,make the following checks of the air brake system on thetractor-trailer combination. These checks are intendedto detect and correct conditions which otherwise couldproduce misleading or Inconclusive test results.1.Check the adjustment of all brakes on both thetractor and trailer(s). Adjust the brakes asrequired.2.Visually check the slack adjuster movement (ifapplicable) to determine that all brakes areactuating and releasing freely. If not, inspectand lubricate the suspect brakes thoroughly. DONOT allow any lubricant on the linings, drums, orrotors.3.Check the air brake system to be sure that it isfree of significant air leaks. Air leakage shouldnot exceed the following values with an airsystem pressure of 655 kPa (95 psi) or moreand the brake pedal released:13.8 kPa (2 psi) per minute, on tractor only.20.7 kPa (3 psi) per minute, on tractor withtrailer combination.34.5 kPa (5 psi) per minute, on tractor withtwo trailer combination.Repair any leakage points if these values areexceeded.4.Drain the reservoirs of any moisture and con-tamination.5.Visually inspect for damage or kinked lines andreplace any lines found to be defective.6.Inspect combination units for loose fifth wheeland kingpin condition. A loose fifth wheel tokingpin fit can exaggerate an unbalanced brakecondition and therefore must be adequatelytightened.Any deficiencies found in the above areas may be con-tributing factors in the brake complaints. These shouldbe considered in the overall analysis of the brakesystem.TEST EQUIPMENTThe test equipment described below and illustrated inFigure 23, with the exception of the Brake Timing Unit, isrequired in conducting the pressure balance, pressurebuild-up rate, and torque balance tests. DOUBLEGLADHAND ASSEMBLYFigure 23Air Brake Test EquipmentCTS-4154YPage 27
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