How to Diagnose a Bad Idler Arm

by Nathan Fisher

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Vehicles with conventional steering use idler arms to connect the ends of the tie rod to the vehicle’s front wheels. Over time the bearings in the arm’s bushings become worn, causing slack in the connection. Generally the only symptom of a bad idler arm is for the steering system to develop “play,” causing the vehicle to not respond to minor movements of the steering wheel. To diagnose a bad idler arm you only have to observe the connections as the wheels are turned.

Step 1

Park the vehicle on a flat, smooth surface. For safety, block the rear wheels and set the parking brake.

Step 2

Start the vehicle and set the front wheels to point straight forward. Move to the front of the vehicle and take up a position where you have a clear view of the idler arm assembly. Ask your assistant to rock the steering wheel back and forth, a few inches at a time.

Step 3

Observe the connection at the end of the idler arm, where the shaft is set into the bushing near the wheel. Use the flashlight if necessary. If the shaft of the idler arm moves in any direction, prior to the wheel beginning to turn, the bushing is bad and the idler arm needs to be replaced.

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