How to Inspect an Idler Arm

An idler arm connects to a car's steering system.

A vehicle's idler arm holds the steering linkage parallel to the ground. The idler arm attaches to the vehicle's chassis on one end, while its other end supports the steering linkage. Two grease fittings let lubricant enter the idler arm's pivot points. Symptoms of a worn idler arm include excessively worn tire edges, a vehicle that wanders or drifts while driving, and loose or erratic steering. During routine maintenance, inspecting the idler arm can alert an observant mechanic to potential suspension and steering problems.

Things You'll Need

• Ruler

Instructions

1. Park the vehicle on a flat and level surface with the front tires pointed straight ahead. If the vehicle has an alignment problem, point the driver's side tire straight ahead.

2. Slide under the vehicle's front end on the passenger's side and locate the idler arm. Follow the tie rods from the wheel to the steering linkage. The idler arm holds the steering linkage near the chassis on one end. A Pitman arm holds the other end of the steering linkage to the steering gear. Tie rods have knuckles with grease fittings on one end and thread into the alignment adjustment nut on the other end. The outer tie rod connects to the wheel and the inner tie rod connects to the steering linkage with the adjustment nut in between.

3. Inspect the idler arm's rubber boot(s). Some idler arm models use one rubber boot and some use two. Rubber boots cover the idler arm's pivot points and hold the idler arm's grease in. Replace any ripped boots.

4. Grab the idler arm to steering linkage knuckle and pull down. Do not force the idle arm down -- allow the idler arm to travel naturally.

5. Measure the distance from the top of the idler arm's knuckle to the bottom of the frame. Record this measurement.

6. Push the idler arm's knuckle up toward the frame. Do not apply excessive force -- allow the idler arm to move naturally. Forcing the idler arm up will flex the steel in the joint and give a false reading.

7. Measure the distance between the top of the knuckle and the bottom of the frame. Compare the two measurements. If the measurement difference exceeds 1/4 inch, replace the idler arm.

Tips & Warnings

• When a vehicle has worn tie rod ends often the idler arm also has excessive wear.

References

• AutoZone: Idler Arm Inspection
• St Joseph Automotive: Inspecting and Replacing Steering Linkage Components (PDF)

Resources

• Euclid Industries: Tech Tips Front End Tips (PDF)