When a vehicle comes in for service, a corner check to inspect the condition of the steering, suspension and drivetrain components should be part of your normal routine. If the reason for service is customer complaints of noises or symptoms that indicate a suspension problem, your inspection will begin with a road test. In addition to verifying your customers specific concern, assess the overall performance of the suspension and steering and listen for any tell-tale noises that may focus your inspection specifically in one area or another.
Excessive body roll, suspension movement during acceleration or braking, or poor stability often indicates worn out struts or shocks. Noises over bumps or while turning can indicate worn strut or shock mounts, as well as other suspension or steering components. A rumbling sound may indicate a bad wheel bearing, and if steering back and forth to shift the vehicle weight from side to side changes the noise, this is likely a sure indicator of a bad wheel bearing.
Clicking or snapping noises during turns or hard acceleration may also indicate a worn constant velocity (CV) joint.
In the shop, begin your inspection with a bounce test. Go to one corner of the vehicle and push down sharply to induce suspension travel. The vehicle should immediately return and settle at ride height with no additional movement. In some situations, a very slight, and single upward bounce above ride height may be normal. Anything more indicates a worn shock or strut.
Keep in mind, however, that vehicles with active or adaptive suspension may have different dampening rates that are only active when the vehicle is running or can change with speed. While a bounce test provides an accurate assessment on most vehicles, be sure to refer to manufacturer testing procedures on vehicles with active suspension.
Before lifting the vehicle, take a ride height measurement in a consistent location at all four corners, for example at the top of the wheel well. While we don’t commonly look up this specification as part of a routine service, even if you’re not measuring at a specific location recommended by the manufacturer, you’re at least making a base determination that the vehicle has an even ride height from side to side.
If there’s a considerable variation, it may indicate a worn or broken spring, and you can focus your inspection closely on that area.
Once you have lifted the vehicle in the air, perform a complete visual inspection of the shocks and struts. Begin by looking for any signs of oil, indicating leakage due to failure of the strut or shock seals. Also closely look at the condition of the dust boots and bump stops.
Inspect for any broken springs and inspect the coil spring perches for rust or corrosion, making sure perch drains are not plugged with dirt or debris, which could lead to rapid corrosion and failure.
On front struts, the wheels should smoothly turn from lock-to-lock. Any resistance, noise or popping sounds from the springs indicate the upper turn bearing is binding.
Check for excessive vertical play from the upper strut or shock mounts, which indicates a collapsed mount. This will result in clunking noises over bumps, and is a common problem heard in both the front and rear.
Also check for loose or worn stabilizer bar links and bushings, both so you don’t accidentally mis-diagnose a strut for the cause of this noise, but also so you can quote them as part of the job, since the stabilizer links almost always need to be removed during strut replacement.
Stabilizer links produce a sharp rattle sound when bad, but stabilizer bar bushings produced a lower thud-type of sound, similar to and often mistaken for upper strut mounts.
Next inspect for worn ball joints and tie rod ends, or any torn or damaged boots. Inspect for any play in the wheel bearings and look closely at the steering knuckle for any signs of damage, particularly for taper fit ball joints or tie rod ends that have been installed with an impact wrench. If the castle nut on a taper-fit joint is far below the hole for the cotter pin, this indicates the joint was installed too deep into the knuckle, and most likely the taper in the knuckle is damaged.
During the visual inspection, also examine the tire wear patterns. Uneven wear patters such as cupping are good indicators of a worn strut. Since the struts are what keeps the vehicle tires firmly planted on the road, a worn strut allows them to bounce, and it’s this constant change in force that causes uneven wear.
Finally, inspect all suspension bushings for play and inspect all CV joints for worn or damaged boots or leaking grease. When preparing an estimate, remember that installing some new components when others are worn won’t restore proper vehicle performance. You can’t install a perfect part into an imperfect system, and performing a thorough corner check will allow you to provide a comprehensive evaluation of vehicle condition, leaving no details overlooked.
