BENDIX BW7257 manual Operational Check/Troubleshooting, Tight or Dragging Brakes

Operational Check

1.Measure the pushrod length (distance from the face of air chamber to the centerline of the pushrod clevis pin) when

fully retracted, step 1. (See Figure 20.)

2.Have an assistant make an 80 to 90 psi brake application. Measure pushrod length again, step 2.

3.Subtract the step 1 dimension from step 2. The difference is the “applied stroke.”

4.Verify that the applied stroke is less than the maximum specified below.

80-90 PSI Brake Application

Verify the correct installation of the control arm. If the self adjusting brake adjuster does not maintain proper applied stroke, it must be replaced.

Troubleshooting

Tight or Dragging Brakes

Check foundation brake components for:

•Control arm anchor bracket not positioned properly (See brake adjuster installation procedures.)

•Brake chamber not fully releasing

–Spring brake not fully releasing

–Pushrod binding on chamber housing

–Air supply not exhausting completely

•Out-of-round brake drums

•Extreme differences in lining-to-drum clearances between shoes on same wheel

•Improper wheel bearing adjustment

•Broken shoe return spring

•Loose brake linings

Excessive Chamber Pushrod Travel

Check foundation brake components for:

•Loose, broken or bent control arm anchor bracket

•Worn camshaft bushings

•Loose air chamber mounting

•Binding camshaft

•Worn clutch assembly (See Checking Release Torque.)

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