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ASE P2 TEST PRIMER: Suspension and Steering


10/18/2013
By Larry Carley

Major components in the suspension include springs (coil, leaf, torsion bar and air springs), shock absorbers and/or struts (twin tube or monotube, low or high pressure gas charged, and some may be electronically adjustable), control arms and bushings, ball joints (which may be an integral part of some unitized control arm assemblies), and sway bar and bushings.
 

Major components in the steering include the steering gear (rack and pinion or recirculating ball, manual or power assisted), power steering pump and hoses (not used with electronic steering), tie rods and tie rod ends, idler arm and center link (used only with recirculating ball steering gear systems), steering stabilizer (if used) and steering column (including flexible couplings that connect the steering gear to the column shaft).

Major components in the suspension include springs (coil, leaf, torsion bar and air springs), shock absorbers and/or struts (twin tube or monotube, low or high pressure gas charged, and some may be electronically adjustable), control arms and bushings, ball joints (which may be an integral part of some unitized control arm assemblies), and sway bar and bushings.

All steering and suspension parts wear over time. Wear increases play and can lead to undesirable changes in wheel alignment, resulting in steering, handling and ride-quality problems, uneven or rapid tire wear, noise or even parts failures. Worn parts cannot be realigned and must be replaced. Parts such as tie rod ends and struts also require realigning the wheels following installation.

Many newer vehicles have electronic steering that use an electric motor to provide power assist. But most older cars have hydraulically assisted power rack and pinion steering. Common problems include fluid leaks at the rack bellows, line fittings and hoses. Internal seal wear can cause a loss of power assist. Worn racks are usually replaced as an assembly (with tie rods) to save labor.

Steering noise may be caused by a worn power steering pump or slipping belt. Power steering pumps require power steering fluid that meets the vehicle’s specifications. Leaky power steering hoses can be replaced with preassembled hoses or custom made-to-order hoses. The power steering system should always be flushed to remove contaminants when replacing a steering rack, pump or hoses.

The suspensions on most vehicles do not require lubricating with chassis grease, but some ball joints, tie rod ends and U-joints on older vehicles or heavy-duty use vehicles may be greasable.

Ball joints, tie rod ends and idler arms that are loose (play exceeds specifications) must be replaced.
Shocks and struts are the most commonly replaced suspension parts due to wear, fluid leakage or damage. Preassembled struts are ready to install and do not require a spring compressor. Electronic shocks and air ride suspensions on older vehicles can often be converted to less expensive conventional shocks/struts when repairs are needed.

Required to pass this section of the P2 test:
1. Identify major steering and suspension components.
2. Identify component function and common reasons for replacement.
3. Identify related items, including lubricants and service tools.
4. Provide basic use, maintenance, installation and warranty information.















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