The sway bar on a car is a rigid length of tubular metal bolted to the right and left sides of the suspension. Most cars use a front and rear sway bar, though some only use a front sway bar. The purpose of a sway bar is to reduce body roll as the vehicle corners. Since it is bolted to the suspension on either side, the sway bar acts as a lever arm, forcing the wheel toward the inside of the turn towards the ground, increasing grip and making the vehicle feel more stable. The sway bar is fastened to the suspension and chassis with bushings and brackets.
Clunking and Rattling
The middle portion of a sway bar on a car bolts to the chassis. Bushings slide onto the bar and then a metal bracket goes over the bushing and the bracket bolts to the chassis. The sway bar is bolted to the suspension at either end with end links that come off the bar at 90-degrees. The end links are bolted to the suspension with a series of bushings, washers and nuts. If the centre bushings are broken, torn or missing, the sway bar will probably move excessively causing clunks and rattles from the front or rear when the vehicle is driven around a corner or even over a rough road in a straight line. If the bushings located on the end links are damaged or missing, similar clunking or rattling symptoms may occur.
Vague Steering and Handling
The bushings hold the sway bars firmly to the vehicle. If the bushings are damaged or missing, the steering may feel less precise than it normally does, since the sway bar moves around excessively. As the vehicle corners, the car may feel less stable, with sloppy handling.
Torn or Missing Bushing
A visual inspection can also reveal other signs that the sway bar bushings are damaged. Lift the vehicle with a heavy-duty floor jack and support it with jack stands. Locate the sway bar under the car, which will be the thin bar that goes from one side of the car to the other. Inspect the end links. There will be bushings at the end of the link where it fastens to the suspension. Ensure the bushings are there and not damaged. Inspect the centre part of the bar, where it bolts to the chassis. Inspect the bushings underneath the brackets to ensure bushings are not damaged, torn or missing.
If it is determined that the sway bar bushings need replacing, remove the sway bar with the appropriate tools. Consult a workshop manual for your specific make and model to determine the exact procedure for removing the bar. Disconnect the sway bar at either end from the suspension and in the middle from the chassis. Remove the old bushings and install the new ones. Reinstall the sway bar.