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Autopapyrus · Isuzu Forward (3rd generation)
https://autopapyrus.com/guides/isuzu/forward/drum-brake-inspection/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Isuzu Forward (3rd generation): Drum Brake Inspection

A drum brake inspection covers checking the linings, drums and actuating components, and adjusting the clearance. The actuation system (hydraulic with a vacuum booster, or air) depends on the load rating and equipment, so some steps are given as a general principle. Check the exact wear limits and clearances against the manufacturer's service manual and the markings on the drum.

Difficulty: Medium Time: 1.5-3 hours (for all wheels on one axle) Steps: 14 Tools: jack and rigid wheel chocks/jack stands, lug wrench, copper or brass hammer, drum puller (if the drum is seized), caliper, drum micrometer (inside gauge) or drum template, feeler gauge, flat-blade screwdriver, wire brush, brake cleaner, gloves, respirator

Part

  • 🔩 If worn, you will need a brake shoe set with linings for the axle, retracting and return springs, a wheel cylinder repair kit (hydraulic) or brake chamber/spring brake chamber (air), a brake drum, and a hub seal

Step by step

14 steps
  1. Park the vehicle on level ground, shut off the engine, and place wheel chocks under the wheels of the other axle. Release the parking brake on the axle you are checking. On air brakes, first drain the air from the system. On hydraulic brakes, make sure the fluid level in the reservoir is correct.
  2. Raise the axle you are checking with a jack and set it on jack stands. Never work under a vehicle supported only by a jack.
  3. Check how the wheel turns without removing the drum: spin the wheel by hand, listen for rubbing and grinding, and check that it turns freely and runs true. Rock the wheel vertically and horizontally to tell hub bearing play apart from brake problems.
  4. Through the inspection windows in the backing plate (if equipped), check how much lining is left. If there are no windows, remove the wheel and drum.
  5. Remove the wheel, then the drum. If the drum is seized, tap lightly around its rim with a copper hammer and back off the shoe adjustment through the inspection hole. Use a puller rather than brute force.
  6. Inspect the linings. Thickness must be above the minimum specified by the manufacturer (on trucks, linings are typically worn down to 4-5 mm above the rivets or to the wear mark; check the exact value in the service manual). Wear should be even along the length of the shoe, with no oil stains, cracks, separation or glazing.
  7. Inspect the drum. The friction surface should be free of deep scoring, grooves, cracks, blue heat spots and out-of-roundness. Measure the inside diameter. The maximum limit is usually cast or stamped on the drum, and if it is exceeded, replace the drum. Machine both drums on an axle to the same size.
  8. Check the springs, shoe support pads, the expanding mechanism (cam or cylinders), rollers and pins. Springs must not be stretched or corroded, pins must move without binding, and grease must be present on the cam and bushings.
  9. Hydraulic brakes: inspect the wheel cylinders. The dust boots should be dry, with no fluid leaks. A leak means the cylinder needs repair or replacement. Check the brake lines and hoses for cracks and corrosion.
  10. Air brakes: check the brake chamber pushrods, their stroke and sealing, and the condition of the slack adjusters (ratchets) and dust boots. Pushrod stroke must be within the tolerance in the service manual. Listen for air leaks with the system pressurized.
  11. Check the wheel bearing and seal. Oil or grease must not get onto the linings. Fix a leaking seal immediately, and replace any oil-soaked linings.
  12. Clean the assembly with brake cleaner. Do not blow off the dust or breathe it in. Reassemble: install the drum and the wheel, then tighten the lug nuts in a crisscross pattern. Use the torque specified by the manufacturer for your axle, and do not tighten by feel.
  13. Adjust the clearance between the linings and the drum according to the service manual, then press the brake pedal several times (on hydraulic brakes, until the pedal feels firm).
  14. Lower the vehicle and test it at low speed in a safe area. Braking should be free of pulling, vibration and noise, and the parking brake should hold on a slope.

Common mistakes and warnings

  • Brakes are a safety system. If you have no experience with truck brakes, especially air brakes, have the work done at a repair shop. Always replace linings, springs and drums as a set for the whole axle, not on one side only. Older linings from some model years may contain asbestos: wear a respirator and never blow the dust off with compressed air.
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