Table 2-2. Unit Troubleshooting-continued
TEST OR INSPECTION
AIRBRAKE SYSTEM (Models WPES-10 and H-9518-1) - continued.
Remove hub and drum assembly for each wheel (Paragraph 2-87). Inspect brakeshoe linings for wear.
Refer to paragraph 2-88.
If brakeshoe lining thickness is greater than 1/8 inch (3.2 mm), adjust service brakes. Refer to
If brakeshoe linings are less than 1/8 inch (3.2 mm) thick, replace brake shoes and adjust brakes.
Refer to Paragraph 2-88.
ONE BRAKE DRAGS.
Check if brake is manually disabled. Refer to Paragraph 2-89.
If disabled, enable it. Refer to Paragraph 2-89.
Tell assistant to pump towing vehicle brake pedal several times while watching air chamber action on
wheel that drags.
If air chamber assembly pushrod moves out and returns quickly as brakes are engaged and released, go
to step 2.
If air chamber assembly pushrod returns slowly, go to step 4.
Raise wheel that drags and spin wheel to check if brake is adjusted too tightly. Refer to Paragraph 2-88.
If wheel is hard to turn, adjust brakeshoes. Refer to Paragraph 2-88.
Remove hub and drum assembly for wheel that drags (Paragraph 2-87) and check for rusted or damaged
brake parts or weak return spring (Paragraph 2-88).
Replace defective components.
Tell assistant to hold down towing vehicle brake pedal. Loosen uppermost hose fitting on air chamber with
slow returing or dragging push rod.
If air chamber assembly pushrod returns quickly, tighten hose fitting and replace airbrake relay valve.
Refer to Paragraph 2-85.
2-60 Change 1