Bushing Testing and Diagnosis
Suspension bushings don’t require regular maintenance like tie rods and ball joints. Tie rods and ball joints should be lubricated on occasion to keep them in top shape, but certain lubricants can kill a bushing.
Bushings are good for absorbing road shock, minor vibrations and noise from other suspension parts without making any noise themselves. However, rubber bushings don’t deal well with heat or petroleum exposure. Heat can cause the rubber to harden and crack while petroleum will dissolve it into jelly. These can become a serious problem if the bushings are located near the exhaust pipe or in a poorly ventilated engine compartment. Transmission coolant can also cut a bushing’s life short. Even when good, rubber bushings can cause excessive body roll in a vehicle. Also, excessive twisting can cause the it to tear.
Bushing Inspection and Diagnosing
A good test drive has a wide range of diving conditions including left and right cornering, hitting bumps, and barking and accelerating. Strut rod and radius arm bushings may not make a noise, but will cause a pull when braking or accelerating. It may require a sudden brake and steer in an empty parking lot to reveal a failed control arm bushing. If the steering wheel seems to have a new “center” after making different turns, the rack and pinion mounting bushings are suspect. Back at the shop, a dry park test should be performed on a lift. One person should rock the steering wheel left and right while the other stands beneath the vehicle and observes the steering and suspension components. While underneath the vehicle, a rubber hammer and pry bar can be employed. If the vehicle is equipped with link pins that utilize the ball and socket-type ends, use the rubber hammer to strike upward on them. A metallic wrap sound will emit from one with excessive internal wear. Prying on a control arm to find 1/8th inch or more of free play (rubber bushing) can reveal when they have reached their life’s end, as well as looking at the tire wear patterns for signs of camber wear. Be sure to also check the sub frame bushings when applicable.
Replacong bushings is usually as simple as replacing the components the bushing presses into. Mainly for saftey reasons, it is suggested to replace body bushings one side at a time. When installing control arms with rubber bushings, the pivot bolt must be tightened with the weight of the vehicle on the wheels. If they are not, then the bushing will be quickly destroyed. Polyurthane bushings do not have this problem though. Replacement of degraded bushings can prove beneficial to both customer and the repair shop. Upgrading them to urethane will not only provide handling improvements for the customer, but can open up the performance modification market to a repair shop.