The never-ending twisting and untwisting of the coil spring (or the torsion bar) lead to inevitable loss of elasticity and spring sag. Coil springs, then, require replacement because they sag in service. A sagged coil spring upsets vehicle trim height resulting in upset wheel alignment angles, steering angles, headlight aiming, braking distribution, riding quality, tire tread life, shock life, and U-joint life.
Coil springs also break. Downsized cars are often forced to carry the same loads as their larger counterparts, mostly because people and their hauling needs did not down-size along with the cars.
The coil spring exerts a tremendous force on the control arm. Before you disconnect either control arm from the knuckle for any service operation, contain the spring with a spring compressor to prevent it from flying out and causing injury.
- To remove a coil spring, raise and support the vehicle by its frame. Let the control arm hang free.
- Remove wheels, shock absorbers, and stabilizer links. Disconnect the outer tie-rod ends from their respective arms.
- Unload the ball joints with a roll-around floor jack.
- Jack under the lower control arm from the opposite side of the vehicle.
- This allows the jack to roll back when the control arm is lowered.
- Position the jack as close to the lower ball joint as possible for maximum leverage against the spring.
- The spring is ready for the installation of the spring compressor.
A coil spring compressor is used to compress the spring before disconnecting some suspension parts.
- There are many different types of spring compressors.
- One type uses a threaded compression rod that fits through two plates, an upper and lower ball nut, a thrust washer, and a forcing nut.
- The two plates are positioned at either end of the spring.
- The compression rod fits through the plates with a ball nut at either end. The upper ball nut is pinned to the rod.
- The thrust washer and forcing nut are threaded onto the end of the rod.
- Turning the forcing nut draws the two plates together and compresses the spring.
- In some cases, it is necessary to break the tapers of both upper and lower ball joints so the steering knuckle can be moved to one side.
When this tool is expanded, it forces the ball joint stud out of the steering knuckle taper. Courtesy of American Honda Motor Co., Inc.
- If the vehicle is equipped with a strut rod, this must be disconnected at the lower control arm.
- Push the control arm down until the spring can be removed. If necessary, a pry bar can be used to remove the spring from its lower seat. Remove the spring and compressor.
- If the same spring is to be reinstalled, leave the compressor in position. If a new spring is to be used, slowly release the pressure on the tool by backing off the forcing nut.
- Compress the new spring prior to installing it.
Following completion of suspension repair jobs, a wheel alignment will be required. This will reposition suspension components so that the car will be safe to drive and will go straight without unusual tire wear.