Drum Brake System: Testing and Inspection

INSPECT BRAKE DRUM
Inspect drum for cleanliness. Check wear of its braking surface by measuring its inside diameter.

Inside diameter "a"
for 2 door vehicle
Standard: 220 mm (8.66 inch)
Service Limit: 222 mm (8.74 inch)
for 4 door vehicle
Standard: 254 mm (10.00 inch)
Service Limit: 256 mm (10.07 inch)

Whenever brake drums are removed, they should be thoroughly cleaned and inspected for cracks, scores, deep grooves.

Cracked, Scored, or Grooved Drum
A cracked, drum is unsafe for further service and must be replaced. Do not attempt to weld a cracked drum.
Smooth up any slight scores. Heavy or extensive scoring will cause excessive brake lining wear and it will probably be necessary to resurface drum braking surface.
If brake linings are slightly worn and drum is grooved, drum should be polished with fine emery cloth but should no be turned.

NOTE: When drum is removed, visually inspect wheel cylinder for brake fluid leakage. Correct leaky point, if any.





INSPECT BRAKE SHOE & LINING
Where lining is worn out beyond service limit, replace shoe.

Thickness "a"
Standard: 6.5 mm (0.24 inch)
Service limit: 3.0 mm (0.12 inch)

If one of brake linings is to service limit, all linings must be replaced at the same time.

CAUTION: Never polish lining with sandpaper. If lining is polished with sandpaper, hard particles of sandpaper will be deposited in lining and may damage drum. When it is required to correct lining, replace it with a new one.





INSPECT WHEEL CYLINDER
Inspect wheel cylinder disassembled parts for wear, cracks, corrosion or damage.

NOTE: Clean wheel cylinder components with brake fluid.





INSPECT ADJUSTER
Check thread of adjuster for sticking and corrosion.





INSPECT SPRINGS
Inspect for damage or weakening. Inspect each part with arrow for rust. If found defective, replace.





INSPECT PARKING SHOE LEVER
Inspect brake shoe lever for free movement against brake shoe web. If defective, correct or replace.