User's Manual
14
BRAKE SYSTEMS DIAGNOSTIC GUIDE
POTENTIAL CONDITION/CAUSE ACTION (SERVICE MANUAL SECTION)
Incomplete release of air chamber after service application:
• Incorrect clevis position Reposition clevis (6)
• Incorrect bracket slot Reposition on correct bracket slot (6)
• Damaged pushrod Replace air chamber (3,6)
• Air chamber return spring failure Replace air chamber (3,6)
• Road debris damage Repair damage (5)
• Blockage in other upstream air system parts Remove blockage (5)
Incomplete release of parking brake after application
of pressure to air chamber:
• Internal cup/cone hang-up Repair or replace cup/cone
• Damaged pushrod Replace pushrod (3,6)
• Diaphragm leak in parking chamber Replace diaphragm or air chamber (3,6)
• Cocked power spring Repair power spring
• Pushrod seal leak Replace seal (5)
• Blockage in other upstream air system parts Remove blockage
Air leaks in parking system:
• Old or broken lines Replace lines
• Pinhole leaks in air line Replace line
• Loose or damaged fittings Tighten or replace fittings
• Damaged or contaminated valve Repair or replace valve
Blockages in service system air lines:
• Inner lining separation Replace chamber air lines
• Plugged lines Remove blockage
• Contamination Remove contamination
Air valves sticking:
• Seals/O-rings damaged Replace seals/O-rings
• External vents blocked Remove blockage
• Low air pressure to valve (see below) Check for blockage
Check compressor
Low air pressure supplied to system:
• Governor failure -
— Incorrect set point Adjust set point
— Contamination Remove contamination
— Damaged valve Repair or replace valve
• Compressor Failure -
— Worn or leaking components Repair or replace
— Damaged components Repair or replace
— Slipping or broken belts or drives Repair or replace
PARKING BRAKE WILL NOT HOLD/
DRAGGING BRAKES