DIAGNOSIS AND TESTING

Transcription

1 2007 Ford F650 : Brakes > Air Brake System General Information > DIAGNOSIS AND TESTING DIAGNOSIS AND TESTING Listen SECTION B: Brake System General Information Air 2007 F Super Duty Workshop Manual DIAGNOSIS AND TESTING Procedure revision date: 09/18/2008 BRAKE SYSTEM Special Tool(s) Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool 73 Digital Multimeter 105 R0051 Flex Probe Kit 418 F090 (105 R025B) Inspection and Verification WARNING WARNING: Before attempting to work on the air brake system, certain precautions must be observed. Since the compression and storage of air can be compared to the energy in a coiled spring which, when released, can present a hazard if not correctly recognized. The wheels of 1/39

2 the vehicle must always be chocked so that depletion of air will not permit the vehicle to roll. WARNING WARNING: Hoses will whip dangerously if disconnected under pressure. WARNING WARNING: Follow the manufacturer's recommended procedures when working on any air devices to avoid injury or damage from parts which, when released, are subject to mechanical (spring) or pneumatic propulsion. WARNING WARNING: As system pressure is drained and the emergency brakes apply, hands must be away from the air chamber push rods and spring actuators, which apply automatically with the loss of pressure. This also applies when checking the service brake system. WARNING WARNING: Reservoirs which are closest to the sources of compressed air (compressors or auxiliary sources) must contain a safety valve in known working order and with sufficient capacity to limit the reservoir pressure to a safe maximum level. WARNING WARNING: Install new air reservoirs only. Used air reservoirs must not be used as replacements. WARNING WARNING: The safety valve must not be installed with a higher than specified value by the reservoir manufacturer, vehicle manufacturer or code to which the reservoir had been manufactured. WARNING WARNING: Various actuators contain powerful internal springs that require special handling procedures. te and be guided by the warning tags on such units. WARNING WARNING: Do not manually adjust the automatic slack adjusters to correct excessive push rod stroke as it may result in reduced brake effectiveness and a vehicle crash. Excessive push rod stroke indicates that a problem exists with the automatic adjuster, with the installation of the 2/39

3 adjuster or with foundation brake components that manual adjustment will not remedy. NOTE: Air chamber push rods have orange stroke indicator markers that warn when the braking system requires adjustment or repair. The orange stripe is painted on the air chamber push rod at the slack adjuster stroke dimension which requires service when visible during brake application. Observe these warnings while investigating all applicable brake system concerns. 1. Verify the concern by operating the system. 2. Visually inspect for obvious signs of wear or damage. Visual Inspection Chart Mechanical Leak from air line(s) Disconnected air line Leak from air chamber(s) Electrical Fuse(s) Wiring harness Loose or corroded connector(s) Relay(s) 3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step. 4. If the concern is not visually evident, verify the symptom. GO to Symptom Chart. System Leakage With the engine stopped and the air reservoirs charged to governor cutout pressure (897 kpa [130 psi] maximum), the rate of pressure drop shall not exceed 7 kpa (1.0 psi) per minute with the service brakes released and spring brakes applied. For air pressure loss concerns, coat the fittings and exhaust ports of the suspected components with a soap solution and check for air bubble formation. Compare bubble formation to allowable leakage specifications. Tighten, repair or install new components as necessary. Inspect air lines for kinks, abrasions and incorrect routing. Repair or reroute as necessary. Push to Connect Fittings There are 2 types of push to connect fittings used in the air brake system: threaded fittings and cartridge type fittings. The push to connect fitting with the threaded end is not a repairable component. If this type of fitting is found to be leaking, worn or damaged, a new fitting must be installed. The cartridge type push to connect fitting is considered part of the air manifold and is repairable. Threaded Push to Connect Fitting 3/39

4 Cartridge Type Push to Connect Fitting Air Chamber Free Stroke WARNING WARNING: Do not manually adjust the automatic slack adjusters to correct excessive push rod stroke as it may result in reduced brake effectiveness and a vehicle crash. Excessive push rod stroke indicates that a problem exists with the automatic adjuster, with the installation of the adjuster or with foundation brake components that manual adjustment will not remedy. NOTE: Air chamber push rods have orange stroke indicator markers that warn when the braking system requires adjustment or repair. The orange stripe is painted on the air chamber push rod at the slack adjuster stroke dimension which requires service when visible during brake application. Free stroke is the amount of slack adjuster movement required to bring the brake shoes and linings into contact with the brake drum. Check the air chamber free stroke as follows: 1. With the brakes released, measure and record the distance from the air chamber face to the center of the large clevis pin. Measurement Without Brake Application 4/39

5 2. Using a lever, extend and hold the air chamber push rod at the point at which the brake shoe and lining is felt to come into contact with the brake drum. 3. Make the same measurement as in Step 1. Measurement with Brake Application 4. Subtract the Step 1 measurement from the Step 3 measurement to obtain the free stroke measurement. For a correctly installed slack adjuster and correctly adjusted brakes, the free stroke must be mm (3/8 5/8 in). A free stroke that is longer than specified is caused by a worn or damaged slack adjuster. Carry out the slack adjuster component test. Refer to Slack Adjuster under Component Tests in this section. If the slack adjuster is OK, inspect the foundation brakes for correct installation, missing, worn or damaged parts. Correct as necessary. Recheck the air chamber free stroke. ise, Vibration and Harshness Concerns For vibration concerns, check the brake drum and foundation brake components at the applicable axle location. Check the brake drum for out of round condition. Refinish or install a new brake drum as necessary. Inspect the foundation brake components for loose mounting, wear, damage and incorrect installation. Repair or install new components as necessary. Symptom Chart Symptom Chart Condition Possible Sources Action The brakes pull or drift Vehicle loading BALANCE vehicle load. 5/39

6 Base brake components GO to Pinpoint Test A. Valves Line restriction CARRY OUT Inspection and Verification in this section. The red brake warning indicator is always ON Generic electronic module (GEM) Low air pressure switches GO to Pinpoint Test B. The low air pressure warning chimes are always ON GEM Low air pressure switches GO to Pinpoint Test C. Brakes do not release or release too slowly Base brake components Valves Line restriction GO to Pinpoint Test D. Brakes insufficient, do not apply or apply too slowly Air chamber free stroke REFER to Air Chamber Free Stroke under Inspection and Verification in this section. Adjustment CARRY OUT Slack Adjuster Manual Adjustment in this section. Water or oil in air supply CARRY OUT Air Dryer test. REFER to Component Tests in this section. Valves, line restriction or base brake components GO to Pinpoint Test E. Excessive oil or water in brake system Air dryer CARRY OUT Air Dryer test. REFER to Component Tests in this section. 6/39

7 Contaminated air source DRAIN and REPRESSURIZE the system with clean dry air. Compressor CARRY OUT Compressor test. REFER to Component Tests in this section. Moisture ejector valve INSTALL a new valve as necessary. Air pressure rises above normal Governor CARRY OUT Governor test. REFER to Component Tests in this section. Air pressure will not rise to normal or rises too slowly Compressor CARRY OUT Compressor test. REFER to Component Tests in this section. Leaks CARRY OUT Leakage tests. REFER to Inspection and Verification in this section. Low air pressure buzzer sounding air pressure gauge reads OK Low air pressure switch Air gauge GO to Pinpoint Test F. Parking brake will not apply or applies too slowly Valve Brake air chamber GO to Pinpoint Test G. Parking brake will not release or releases too slowly Valve Air supply GO to Pinpoint Test H. Pinpoint Tests PINPOINT TEST A: THE BRAKES PULL OR DRIFT Test Step Result / Action to Take A1 CHECK VEHICLE LOADING 7/39

8 Check the vehicle for balanced load. Is the vehicle evenly loaded? GO to A2. BALANCE vehicle load. RETEST the brakes. A2 CHECK THE TIRES Check the tires for uneven wear. Check for mismatched tires. Check the tires for incorrect inflation and installation. Are the tires OK? GO to A3. CORRECT the tire concern. RETEST the brakes. A3 CHECK THE AIR CHAMBER STROKE Measure the air chamber stroke at all wheels when the brakes are applied. Refer to DOT Adjusted Air Chamber Stroke Limits in Component Tests portion of this section. Is the air chamber stroke equal and within specification at all wheels? GO to A4. INSPECT the cam bearings, INSTALL new as necessary. CHECK the operation of the slack adjuster. REFER to Component Tests in this section. RETEST the system. A4 CHECK FOR LEAKS Check for air leaks at the valves, lines and brake air chambers when the brakes are applied. Were any leaks found? REPAIR or INSTALL new components as necessary. RETEST the brakes. GO to A5. A5 CHECK THE AIR CHAMBER PRESSURE Measure the air pressure at the brake 8/39

9 air chambers when the brakes are applied. Is the pressure equal at all brake air chambers? GO to A7. GO to A6. A6 CHECK THE ABS MODULATORS Measure the air pressure at the ABS modulators. Is the pressure equal at all ABS modulators? CHECK the air line(s) for restrictions. INSTALL a new air line(s) as necessary. RETEST the brakes. INSTALL a new suspect ABS modulator. RETEST the brakes. A7 CHECK THE BRAKE DRUM Check the brake drums for incorrect installation, out ofround condition, cracks or other damage. Are the brake drums OK? CHECK the base brake components for wear, damage, mismatched parts, contamination and incorrect installation. REPAIR or INSTALL new components as necessary. RETEST the brakes. REPAIR or INSTALL new brake drums as necessary. TEST the system for normal operation. PINPOINT TEST B: THE RED BRAKE WARNING INDICATOR IS ALWAYS ON NOTICE: Use the flex probe kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes. Test Step Result / Action to Take B1 RETRIEVE CODES FROM THE GEM MODULE Place the vehicle in PARK or NEUTRAL. Connect the scan tool. Enter the following diagnostic mode on the scan tool: Retrieve and Document Continuous DTCs. Enter the following diagnostic mode on the scan tool: Clear Continuous DTCs. Enter the following diagnostic mode on the scan tool: On Demand Self Test. If unable to carry out the On Demand Self Test or communicate with the GEM module, refer to Multifunction Electronic Modules. Are any codes present? If C1161, GO to B5. If C1223, GO to B12. If C1225, GO to B14. If B1342, INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. GO to B2. 9/39

10 B2 CHECK THE GEM FOR CORRECT INPUTS Ignition ON. Enter the following diagnostic mode on the scan tool: Monitor the GEM PID IGN_R. Do the PIDs read ON? GO to B3. INSTALL a new ignition switch. REFER to Steering Column Switches. TEST the system for normal operation. B3 CHECK THE GEM FOR CORRECT INPUTS Start the engine. Enter the following diagnostic mode on the scan tool: Monitor the GEM PID LOW_AIR. Allow air brake pressure to rise above 80 psi. Press the yellow air park brake knob to release (bleed) air pressure below 50 psi. Does the PID read OFF then ON when the air pressure drops below 448 kpa (65 psi)? GO to B4. GO to B5. If PID always reads ON, GO to B5. If PID always reads OFF, GO to B8. B4 CHECK THE GEM OUTPUTS (RED BRAKE WARNING LAMP) Start the engine. Enter the following diagnostic mode on the scan tool: Monitor the RED Brake Warning Lamp while toggling the Active Command BRAKE LAMP on and off. Does the lamp illuminate with active command? INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. GO to B12. If lamp is always on, GO to B13. B5 CHECK THE PRIMARY AND SECONDARY LOW PRESSURE SWITCH INPUTS Start the engine. Enter the following diagnostic mode on the scan tool: Monitor the GEM PID LOW_AIR while disconnecting the primary and secondary low pressure switches. Verify the air pressure above 552 kpa (80 psi). Does the PID read OFF with both switches disconnected? CHECK air pressure low in system. REFER to the compressor test in Component Tests portion of this section. If the primary switch is ON, GO to B6. If secondary switch is ON, GO to B7. B6 CHECK THE PRIMARY LOW PRESSURE SWITCH OR CIRCUIT 218 (WH/VT) SHORT TO GROUND Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between primary low pressure switch C314, circuit 218 (WH/VT), pin 2 and chassis ground. 10/39

11 INSTALL a new primary low pressure switch. TEST the system for normal operation. REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance greater than 10,000 ohms? B7 CHECK THE SECONDARY LOW PRESSURE SWITCH OR CIRCUIT 218 (WH/VT) SHORT TO GROUND Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between secondary low pressure switch C315, circuit 218 (WH/VT), pin 2 and chassis ground. INSTALL a new secondary switch. TEST the system for normal operation. REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance greater than 10,000 ohms? B8 CHECK THE PRIMARY AND SECONDARY LOW PRESSURE SWITCH CIRCUITS 218 (WH/VT) Start the engine. Monitor the GEM PID LOW_AIR while jumping the primary low pressure switch. Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Connect a jumper wire between primary low air pressure switch C314, circuit 218 (WH/VT), pin 2 to chassis ground. 11/39

12 Monitor the GEM PID LOW_AIR while jumping the primary low pressure switch C314, circuit 218 (WH/VT), pin 2 to chassis ground. Connect a jumper wire between secondary switch C315, circuit 218 (WH/VT), pin 2 to chassis ground. Monitor the GEM PID LOW_AIR while jumping secondary low pressure switch C315, circuit 218 (WH/VT) pin 2 to chassis ground. If primary switch always reads OFF, GO to B9. If secondary switch always reads OFF, GO to B10. GO to B11. Does the PID read OFF then ON when the switch connectors are grounded? B9 CHECK THE PRIMARY LOW PRESSURE SWITCH OR CIRCUIT 1203 (BK/LB) FOR AN OPEN CIRCUIT Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between primary low pressure switch C314, circuit 1203 (BK/LB), pin 1 and ground. INSTALL a new primary switch. TEST the system for normal operation. REPAIR circuit 1203 (BK/LB). TEST the system for normal operation. Is the resistance less than 5.0 ohms? 12/39

13 B10 CHECK THE SECONDARY LOW PRESSURE SWITCH OR CIRCUIT 1203 (BK/LB) FOR AN OPEN CIRCUIT Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between secondary low pressure switch C315, circuit 1203 (BK/LB), pin 1 and ground. INSTALL a new secondary switch. TEST the system for normal operation. REPAIR circuit 1203 (BK/LB). TEST the system for normal operation. Is the resistance less than 5.0 ohms? B11 CHECK CIRCUIT 218 (WH/VT) FOR AN OPEN CIRCUIT Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between primary low pressure switch C314, circuit 218 (WH/VT), pin 2 and GEM C202, circuit 218 (WH/VT), pin 4. Measure the resistance between secondary low pressure switch C315, circuit 218 (WH/VT), pin 2 and GEM C202, circuit 218 (WH/VT), pin 4. INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. 13/39

14 REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance less than 5.0 ohms? B12 CHECK CIRCUIT 977 (VT/WH) FOR AN OPEN CIRCUIT Disconnect: Instrument Panel Cluster C215C. Disconnect: GEM C202. Measure the resistance between instrument panel cluster C215, circuit 977 (VT/WH), pin 9 and GEM C202, circuit 977 (VT/WH), pin 12. GO to B13. REPAIR circuit 977 (VT/WH). TEST the 14/39

15 system for normal operation. Click to Enlarge Is the resistance less than 5.0 ohms? B13 CHECK CIRCUIT 977 (VT/WH) FOR A SHORT TO GROUND Measure the resistance between GEM C202, circuit 977 (VT/WH), pin 12 and chassis ground. GO to B14. REPAIR circuit 977 (VT/WH). TEST the system for normal operation. Is the resistance greater than 10,000 ohms? 15/39

16 B14 CHECK CIRCUIT 977 (VT/WH) FOR A SHORT TO B+ Measure the voltage between GEM C202, circuit 977 (VT/WH), pin 12 and ground. Is the voltage greater than 10.0 volts? REPAIR circuit 977 (VT/WH). TEST the system for normal operation. GO to B15. B15 CHECK THE INSTRUMENT PANEL CLUSTER BRAKE WARNING LAMP Remove the instrument panel cluster red brake warning bulb. Check the instrument panel cluster red brake warning bulb. Is the bulb OK? GO to B16. INSTALL a new bulb. TEST the system for normal operation. B16 CHECK THE INSTRUMENT PANEL CLUSTER WARNING LAMP CIRCUIT Ignition ON. Measure the voltage between instrument panel cluster C215, circuit 977 (VT/WH), pin 9 and ground. INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. REPAIR or INSTALL a new instrument panel cluster. TEST the system for normal operation. Is the voltage greater than 10.0 volts? PINPOINT TEST C: THE LOW AIR PRESSURE WARNING CHIMES ARE ALWAYS ON NOTICE: Use the flex probe kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes. Test Step Result / Action to Take C1 RETRIEVE CODES FROM THE GEM MODULE Place the vehicle in PARK or NEUTRAL. Connect the scan tool. 16/39

17 Enter the following diagnostic mode on the scan tool: Retrieve and Document Continuous DTCs. Enter the following diagnostic mode on the scan tool: Clear Continuous DTCs. Enter the following diagnostic mode on the scan tool: On Demand Self Test. If unable to carry out On Demand Self Test or communicate with module, refer to Multifunction Electronic Modules. Are any codes present? If DTC C1161, GO to C5. If DTC B1342, INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. GO to C2. C2 CHECK THE GEM OUTPUTS (GEM INTERNAL CHIMES) Monitor the audible GEM internal warning chimes while toggling the active command CHIME on and off. Does the warning chime sound with the active command? GO to C3. INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. C3 CHECK THE GEM FOR CORRECT INPUTS Start the engine. Monitor the GEM PID IGN_R. Does the PID read YES? GO to C4. GO to Steering Column Switches. C4 CHECK THE GEM FOR CORRECT LOW PRESSURE INPUTS Ignition ON. Allow the air brake pressure to rise above 550 kpa (80 psi). Press the yellow air park brake knob to release (bleed) air pressure below 345 kpa (50 psi). Monitor the GEM PID LOW_AIR. Does the PID read OFF then ON when the air pressure drops below 450 kpa (65 psi). GO to C8. GO to C5. If PID always reads ON, GO to C5. If PID always reads OFF, GO to C8. C5 CHECK THE PRIMARY AND SECONDARY LOW PRESSURE SWITCH INPUTS Ignition ON. Verify the air pressure is above 550 kpa (80 psi). Monitor the GEM PID LOW_AIR while disconnecting the primary and secondary low pressure switches. Does the PID read OFF with both switches disconnected? CHECK if air pressure is low in system. GO to the Compressor test in the Component Tests portion of this section. If primary switch always reads ON, GO to C6. If secondary switch always reads ON, GO to C /39

18 C6 CHECK THE PRIMARY LOW PRESSURE SWITCH OR CIRCUIT 218 (WH/VT) A SHORT TO GROUND Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between primary low pressure switch C314, circuit 218 (WH/VT), pin 2 and chassis ground. INSTALL a new primary switch. TEST the system for normal operation. REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance greater than 10,000 ohms? C7 CHECK THE SECONDARY LOW PRESSURE SWITCH OR CIRCUIT 218 (WH/VT), FOR A SHORT TO GROUND Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. Disconnect: GEM C202. Measure the resistance between secondary low pressure switch C315, circuit 218 (WH/VT), pin 2 and chassis ground. INSTALL a new secondary switch. TEST the system for normal operation. REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance greater than 10,000 ohms? C8 CHECK PRIMARY AND SECONDARY LOW PRESSURE 18/39

19 SWITCH CIRCUIT 218 (WH/VT) Start the engine. Disconnect: Primary and Secondary Low Air Pressure Switches C314, C315. NOTE: Use a fused jumper wire to ground the primary switches. Monitor the GEM PID LOW_AIR while jumping primary low pressure switch C314, circuit 218 (WH/VT), pin 2 to chassis ground. NOTE: Use a fused jumper wire to ground the primary switches. Monitor the GEM PID LOW_AIR while jumping secondary low pressure switch C315, circuit 218 (WH/VT), pin 2 to chassis ground. If primary switch always reads OFF, GO to C9. If secondary switch always reads OFF, GO to C10. GO to C11. Does the PID read OFF then ON when the switch connectors are grounded? C9 CHECK THE PRIMARY LOW PRESSURE SWITCH OR CIRCUIT 1203 (BK/LB) FOR AN OPEN CIRCUIT Disconnect: GEM C202. Measure the resistance between primary low pressure 19/39

20 switch C314, circuit 1203 (BK/LB), pin 1 and ground. INSTALL a new primary switch. TEST the system for normal operation. REPAIR circuit 1203 (BK/LB). TEST the system for normal operation. Is the resistance less than 5.0 ohms? C10 CHECK THE SECONDARY LOW PRESSURE SWITCH OR CIRCUIT 1203 (BK/LB) FOR AN OPEN CIRCUIT Disconnect: GEM C202. Measure the resistance between secondary low pressure switch C315, circuit 1203 (BK/LB), pin 1 and ground. INSTALL a new secondary switch. TEST the system for normal operation. REPAIR circuit 1203 (BK/LB). TEST the system for normal operation. Is the resistance less than 5.0 ohms? C11 CHECK CIRCUIT 218 (WH/VT) FOR AN OPEN CIRCUIT Disconnect: GEM C202. Measure the resistance between primary low pressure switch C314, circuit 218 (WH/VT), pin 2 and GEM C202, circuit 218 (WH/VT), pin /39

21 Measure the resistance between secondary low pressure switch C315, circuit 218 (WH/VT), pin 2 and GEM C202, circuit 218 (WH/VT), pin 4. INSTALL a new GEM. REFER to Multifunction Electronic Modules. TEST the system for normal operation. REPAIR circuit 218 (WH/VT). TEST the system for normal operation. Is the resistance less than 5.0 ohms? PINPOINT TEST D: BRAKES DO NOT RELEASE OR RELEASE TOO SLOWLY Test Step Result / Action to Take D1 CHECK THE FOOT CONTROL VALVE Operate and release the foot control valve. Observe the movement of the foot control valve. Does the foot control valve return to the fully released position when it is released? GO to D2. REMOVE the obstruction. REPAIR or INSTALL a new foot control valve as necessary. TEST the system for normal operation. D2 CHECK THE AIR LINES FOR RESTRICTIONS 21/39

22 Inspect the air lines and check for a kinked or pinched condition. Are the air lines OK? GO to D3. CORRECT the kinked or pinched condition. TEST the system for normal operation. D3 CHECK THE BRAKE AIR CHAMBERS NOTE: For balanced braking, brake chamber diaphragm installation must be done in axle sets. Check for leaks at the spring brake portion of the brake air chambers. Are the brake air chambers OK? GO to D4. REPAIR or INSTALL new brake air chambers as necessary. TEST the system for normal operation. D4 CHECK THE BASE BRAKE COMPONENTS Check the base brake components for binding, weak springs and incorrect installation. Are the components OK? REPAIR or INSTALL a new quick release valve. TEST the system for normal operation. REPAIR or INSTALL new components as necessary. TEST the system for normal operation. PINPOINT TEST E: BRAKES INSUFFICIENT, DO NOT APPLY OR APPLY TOO SLOWLY Test Step Result / Action to Take E1 CHECK VEHICLE LOADING Check for vehicle overloading. Is the vehicle overloaded? CORRECT as necessary. TEST the system for normal operation. GO to E2. E2 CHECK THE FOOT CONTROL VALVE Operate the foot control valve. Check whether the foot control valve can move to the fully operated position. Does the foot control valve operate OK? GO to E3. REMOVE the obstruction. REPAIR or INSTALL a new foot control valve as necessary. E3 CHECK THE AIR CHAMBER STROKE Check the air chamber 22/39

23 stroke. Refer to Slack Adjuster for the DOT Adjusted Air Chamber Stroke Limits in the Component Tests portion of this section. Is the air chamber stroke within specification? GO to E4. CARRY OUT slack adjuster manual adjustment in this section. E4 CHECK THE SYSTEM AIR PRESSURE Check air delivery pressure to the brake air chambers. Is delivery pressure at least 621 kpa (90 psi)? GO to E5. CARRY OUT the compressor and governor tests. REFER to Component Tests in this section. INSTALL a new air compressor or governor as necessary. E5 CHECK THE BASE BRAKE COMPONENTS Access the base brake components. Check the components for wear, damage or incorrect installation. Are the components OK? INSPECT the system for air line kinks, restrictions and component leaks. CORRECT as necessary. TEST the system for normal operation. REPAIR or INSTALL new components as necessary. TEST the system for normal operation. PINPOINT TEST F: LOW AIR PRESSURE BUZZER SOUNDING AIR PRESSURE GAUGE READS OK Test Step Result / Action to Take F1 CHECK THE LOW AIR PRESSURE SWITCH Disconnect the electrical connector at the low air pressure switch. Does the low air pressure buzzer continue? REPAIR or INSTALL a new air pressure buzzer or circuit, if necessary. REFER to Instrumentation and Warning Chimes. TEST the system for normal operation. GO to F2. F2 CHECK THE AIR GAUGE Compare the air gauge to a known good gauge. The original air gauge must be within 48 kpa (7 psi) of the known good gauge. Is the air gauge OK? INSTALL a new low air pressure switch. TEST the system for normal operation. INSTALL a new air gauge. TEST the system for normal operation. 23/39

24 PINPOINT TEST G: PARKING BRAKE WILL NOT APPLY OR APPLIES TOO SLOWLY Test Step Result / Action to Take G1 CHECK THE RELEASE BOLT Check the brake air chamber to determine if the spring brake is caged with the release bolt. Is the spring brake caged? RELEASE the caged spring brake. TEST the system for normal operation. GO to G2. G2 CHECK THE PARKING BRAKE CONTROL VALVE WARNING: To avoid injury, keep clear of the air chamber push rod when brakes are applied or when air is exhausted from the system. Disconnect the output line at the parking brake control valve. Does the parking brake operate? REPAIR or INSTALL a new parking brake control valve. TEST the system for normal operation. GO to G3. G3 CHECK THE QUICK RELEASE VALVE WARNING: To avoid injury, keep clear of the air chamber push rod when brakes are applied or when air is exhausted from the system. Loosen the input line at the quick release valve. Does the quick release valve operate? GO to G4. REPAIR or INSTALL a new quick release valve. TEST the system for normal operation. G4 CHECK THE BRAKE AIR CHAMBER WARNING: To avoid injury, keep clear of the air chamber push rod when brakes are applied or when air is exhausted from the system. Disconnect the slack adjuster from the air chamber push rod. Operate the parking brake. Does the air chamber push rod fully extend? INSPECT the base brake components. REPAIR or INSTALL new components as necessary. TEST the system for normal operation. REPAIR or INSTALL a new brake air chamber. TEST the system for normal operation. PINPOINT TEST H: PARKING BRAKE WILL NOT RELEASE OR RELEASES TOO SLOWLY Test Step Result / Action to Take H1 CHECK THE PARKING BRAKE CONTROL With the parking brake released, 24/39

25 loosen the output line fitting at the parking brake control valve and check for air pressure at the fitting. Is air pressure present at the output line fitting? GO to H2. REPAIR or INSTALL a new parking brake control valve. TEST the system for normal operation. H2 CHECK THE AIR PRESSURE WARNING: To avoid injury, keep clear of the air chamber push rod when brakes are applied or released. With the parking brake released, loosen the input fitting at the air chamber spring brake chamber. Check for air pressure at the fitting. Is air pressure present? GO to H3. CORRECT the obstruction in the air supply path from the parking brake control valve to the brake air chamber. TEST the system for normal operation. H3 CHECK THE BRAKE AIR CHAMBER WARNING: To avoid injury, keep clear of the air chamber push rod when brakes are applied or released. Manually release the brake air chamber. Refer to Drum Brake. Does the parking brake release? REPAIR or INSTALL a new brake air chamber. TEST the system for normal operation. REPAIR worn or damaged components in the base brake system causing the binding condition. TEST the system for normal operation. Component Tests Compressor Operation and Leakage 1. Bleed both the primary and secondary reservoirs down to 586 kpa (85 psi) as measured with a test gauge. Run the engine at full governed rpm until the air pressure in the reservoirs reaches 689 kpa (100 psi). If the pressure buildup time exceeds 40 seconds, the compressor is not operating correctly and one or more of the following conditions may exist: The engine air cleaner or compressor inlet hose, the source of fresh air for the compressor, is clogged. Excessive air system leakage. The compressor drive gear is slipping. Restricted discharge cavity in the compressor or restricted discharge line. The discharge valve is stuck or broken. The unloader piston inside the compressor is stuck. Excessively worn compressor piston rings or cylinder walls. The governor is out of adjustment or fouled. The air compressor has 3 possible sources of leakage: engine coolant, lubricating oil and air. Coolant leakage can be checked by pressurizing the cylinder head water cavity to 414 kpa (60 psi) for 5 minutes. Make sure there are no leaking fittings by using the soap bubble test. If the pressure drops in the system, this leakage is unacceptable and a new compressor 25/39

26 must be installed. Oil leakage can be checked visually at the compressor end caps, crankshaft seal and the base plate. If the leakage cannot be corrected by correctly tightening the end cap and base plate retainer bolts, a new compressor or gasket must be installed. The compressor can be checked for air leakage at the discharge and air inlet valves. With the engine stopped and air system pressure at kpa ( psi), discharge valve leakage can be detected by listening at the compressor intake for the sound of escaping air. With 827 kpa (120 psi) of air pressure applied to the unloader cavity, and with the air inlet housing removed, check for leaks by squirting oil around the unloader plunger and stem. If leaks are found, install a new compressor or unloader mechanism through the air inlet cavity. Air Dryer NOTE: A small amount of oil in the system is normal and should not, in itself, be considered a reason to install a new desiccant cartridge. The air dryer must be inspected every 900 operating hours or 40,000 km (25,000 miles), or every 3 months. 1. Check for moisture in the air brake system by opening the reservoir drain cocks or valves and checking for water. If moisture is found, a new air dryer desiccant may need to be installed; however, consider the following conditions before installing the desiccant cartridge. An outside air source has been used to charge the system. This air did not pass through the air dryer. Air use is exceptionally high and not normal for a highway vehicle. This can be due to accessory air demands or some unusual air requirement that does not allow the compressor to load and unload in the usual way. Check for excessive air system leaks. The air dryer has been installed in a system that has been previously used without an air dryer. This type of system will be saturated with moisture and it can take several weeks of operation for the system to dry out. Location of the air dryer is too close to the air compressor. There must be a minimum of 1.8 m (6 ft) of metal tubing between the compressor discharge port and air dryer supply port. Vehicles operating in areas where more than a 17 C (30 F) range of temperature occurs in one day can have small amounts of water accumulating in the air brake system. Under these conditions, small amounts of water should not be considered an indication that the air dryer is not working. 2. Check the retaining bolt torque. Tighten loose bolts to specified torque. 3. Check the operation of the end cover check valve. Install an air pressure test gauge in the supply reservoir. While observing the test air gauge, start the engine and allow the system air pressure to reach governor cut out. The purge valve will be open when the governor cut out pressure is reached. Allow 2 minutes for completion of the purge cycle before testing the check valve. A quick loss of pressure can indicate a worn or damaged check valve. Check the purge valve exhaust to confirm a worn or damaged check valve. Use a soap solution to check air leakage. Air leakage must not exceed a 2.5 cm (1 in) bubble in 5 seconds. Install a new dryer as necessary. 4. While the compressor is loaded, coat the exhaust with a soap 26/39

27 solution and check for air leaks at the purge valve. 5. Check the operation of the safety valve. While the compressor is loaded, pull the exposed stem. While the stem is held, there must be an exhaust of air. The valve must reseat when the stem is released. 6. Check the operation of the end cover heater and thermostat assembly during cold weather operation. Valve Modulator With the ignition or engine control on, check for power at the dryer electrical terminal with a voltmeter or test light. On a single terminal air dryer, check between the electrical terminal in the vehicle wiring harness connector and the metal end cover. For dual terminal air dryers, check between the 2 electrical terminals in the vehicle wiring harness connector. If there is no voltage, look for a blown fuse, broken wires or corrosion in the vehicle wiring harness. Turn off the ignition switch and cool the end cover assembly to below 4 C (40 F). Using an ohmmeter, check resistance of the heater element between the electrical terminal and the metal end cover. On the dual terminal end cover, check the resistance of the heater element between the 2 terminals. The resistance should be 2.0 to 4.0 ohms for a 12 volt, 60 watt end cover, and 4.0 to 7.0 ohms for a 24 volt, 120 watt end cover. These resistance values apply to either single or dual terminal air dryer end covers. NOTICE: Do not remove the heater and thermostat assembly unless a new component is available as it will be damaged during removal. Warm the end cover to over 32 C (90 F) and recheck the resistance of the heater element. The resistance must exceed 1,000 ohms for both single and dual terminal air dryers. If the resistance values are within the given limits, the thermostat and heater are operating correctly. If the resistance values are outside the limits, install a new heater and thermostat assembly. 1. Chock the wheels. Charge the air brake system to governor cut out pressure. 2. Place the parking brake control valve in the PARK position. Make sure that the spring brakes apply promptly. Remove one line or plug from the delivery port of the valve and install a test gauge known to be accurate. Place the parking brake control valve in the RELEASE position. Make sure that the spring brakes release fully. 3. With the parking brake control valve in the RELEASE position, note the gauge pressure reading. The correct spring brake hold off pressure setting is kpa ( psi). If the pressure reading is incorrect, install a new modulator valve. 4. Place the parking brake control valve in the PARK position. The gauge reading should drop to zero promptly. A lag of more than one second in drop of pressure indicates incorrect operation of the single check valve (within the modulator valve). 5. With the parking brake control valve in the PARK position, fully apply the service brakes with the foot control valve several times and see if 27/39

28 a pressure reading increase occurs on the gauge each time the foot control valve is applied. If a pressure reading does not occur, repair or install a new modulator valve. 6. Place the parking brake control valve in the RELEASE position. Determine the reservoir which supplies the balance port and drain completely. 7. Apply the foot control valve several times and see if the pressure reading on the gauge decreases each time the foot control valve is applied. After the foot control valve has been applied several times, pressure on the gauge will drop to the point where release of the spring brakes will no longer occur. Valve Modulator Leakage Place the parking brake control valve in the RELEASE position. Using a soap solution, coat the modulator valve exhaust and vent hole in the proximity of the adjusting screw. Slight bubble leakage is permitted. If the modulator valve does not function as described, or if the leakage is excessive, repair or install a new valve as necessary. Valve Quick Release 1. With the air brake system fully charged, apply the brakes. Observe the brake action on the wheels controlled by the quick release valve or relay valve in question. The brakes should apply promptly. 2. Release the brakes and inspect to make sure the air pressure is exhausted rapidly from the exhaust port. Make sure the exhaust port is not restricted. 3. Disassemble and clean the quick release valve, if required, and retest. If the valve does not seat or operates incorrectly, install a new quick release valve. 4. With the brakes applied, coat the exhaust port with a soap solution and inspect for leaks. Leakage is not permissible. 5. Disassemble and clean the quick release valve. If the valve does not seat or operates incorrectly, install a new quick release valve. Valve Parking Brake Control 1. Connect an 827 kpa (120 psi) air source to the supply port. An accurate test gauge should be placed in line with the supply line (use a T fitting to do this). This provides a means of controlling the supply pressure. A small valve with a gauge should be connected to the delivery port. 2. With 827 kpa (120 psi) supply pressure and the button pulled out (APPLIED position), check that leakage at the exhaust port and at the plunger stem does not exceed a 25.4 mm (1 in) bubble in 5 seconds. There should be no leakage between the upper and lower body. 3. Push the button in (RELEASED position). Leakage at the exhaust port and at the plunger should not exceed a 25.4 mm (1 in) bubble in 3 seconds. 4. Reduce the supply pressure. At a pressure of kpa (35 45 psi), the button should pop out automatically, exhausting the delivery volume. Low Air Pressure Switch 1. Exhaust the brake system pressure and note the pressure at which 28/39

29 the warning buzzer sounds. The contacts in the low air pressure switch should close the circuit to the low air brake warning chime as the reservoir air pressure approaches 414 kpa (60 psi). 2. If the buzzer does not sound during discharge or if a sounding buzzer does not stop during buildup, when this range is reached, the electrical connections are loose or the low air pressure switch is not operating correctly. Check and tighten the electrical connections or install a new low air pressure switch. Retest the system. Valve Relay 1. Fully charge the air brake system and adjust the brakes. 2. Make several brake applications and check for prompt application and release at all appropriate wheels. If a brake is slow to apply or release, make sure the brake camshaft is correctly lubricated and new brake components are installed if necessary before proceeding. 3. With the foot control valve in the RELEASED position, coat the relay valve exhaust port with a soap solution and check for inlet valve and valve guide O ring leakage. A 25.4 mm (1 in) bubble in 5 seconds leakage is permitted. 4. Make and hold a foot control valve application. Coat the relay valve exhaust port with a soap solution and check for leakage. A 25.4 mm (1 in) bubble in 3 seconds leakage is permitted. 5. NOTE: If leakage is detected, installing a new inlet/exhaust valve may correct the problem. If leakage still occurs, leakage may be caused by the relay piston O ring or exhaust valve seat. Make and hold a foot control valve application. Coat the outside of the relay valve body in the area where the cover joins the body to check for cover O ring leakage. leakage is permitted. If the relay valve does not function as described above, or if leakage is excessive, it is recommended that the relay valve be repaired or install a new relay valve. Valve Safety The safety valve is located on the air reservoir. With air pressure in the system, pull the exposed end of the safety valve stem which removes the spring load from the ball check valve. Air should exhaust from the valve's exhaust port. Release the stem; the airflow should stop. If the safety valve does not operate as described, install a new valve. Valve Automatic Moisture Ejector With the system charged to 689 kpa (100 psi), make several brake applications and note each time an application is made whether or not an exhaust of air occurs at the manual release port of the automatic moisture ejector valve. If no air comes out, push the wire stem. If air still does not come out, the valve is plugged. Remove, disassemble and clean the valve. The automatic moisture ejector valve functions as reservoir pressure is reduced. Excessive leakage in the air system will cause constant exhausting of the valve. Repair of the air brake system should restore the automatic moisture ejector valve to normal operation. Valve Brake Pedal Check the delivery pressure of both the primary and secondary circuits using test gauges known to be accurate in the appropriate delivery ports of the foot control valve. Depress the treadle to several positions, between the fully RELEASED and fully APPLIED positions, and check the delivered pressure on the test gauges to see that it varies proportionately with the movement of the treadle. When the treadle is fully depressed, the reading on the test gauge should fall to zero promptly when the treadle is released. te that the primary (green) circuit delivery pressure will be about 13.7 kpa (2 psi) greater than the secondary circuit (red) delivery pressure with primary and secondary circuit supply reservoirs at the same pressure. This is normal for the foot control 29/39

30 valve. Any increase in normal stopping distance is a cause for concern and should be investigated. Although the vehicle air brake system may continue to function, the vehicle should not be operated until the necessary repair has been completed and both braking circuits are operating normally. Valve Brake Pedal Leakage Check leakage as follows: Governor Make and hold full brake application. Coat the exhaust port and body of the foot control valve with soap solution. Leakage must not exceed a 25.4 mm (1 in) bubble in 3 seconds in both the APPLIED and RELEASED positions. The governor for the air compressor used is mounted on the compressor. Install a test gauge in the air lines, in the supply or service reservoir. Run the engine to build up air pressure. te the reading on the test gauge at which the pressure stops rising. This is the point that the governor shuttles the compressor unloader piston and stops the compression cycle of the compressor. This is the compressor cut out pressure. The compressor cut out pressure must be 897 kpa (130 psi) maximum. If the instrument panel air gauge is used, the pressure must range between kpa ( psi), allowing for gauge accuracy. With the engine running, slowly reduce the amount of air pressure in the system by applying and releasing the brakes. te on the gauge the level at which the pressure starts to build up again. This is the point that the governor releases the compressor unloader piston and starts the compression cycle of the compressor. This is the compressor cut in pressure. The compressor cut in pressure must be 766 kpa (111 psi) minimum. If the governor does not control the compressor to the above specifications, a new governor must installed. Before installing a new governor, check the accuracy of the instrument panel air gauge with a test gauge. With the governor in its unloaded position and approximately kpa ( psi) reservoir pressure, check for leaks at the base of the governor where it mounts to the compressor and repair as required. The governors is not adjustable. If the governor does not operate as specified, install a new governor. Slack Adjuster Bedix WARNING WARNING: Do not manually adjust the automatic slack adjusters to correct excessive push rod stroke as it may result in reduced brake effectiveness and a vehicle crash. Excessive push rod stroke indicates that a problem exists with the automatic adjuster, with the installation of the adjuster or with foundation brake components that manual adjustment will not remedy. NOTE: Air chamber push rods have orange stroke indicator markers that warn when the braking system requires adjustment or repair. The orange stripe is painted on the air chamber push rod at the slack adjuster stroke dimension which requires service when visible during brake application. 1. NOTE: A loud clicking sound will be heard when turning the hex extension counterclockwise. Turn the hex extension 1/2 turn counterclockwise. 30/39