Front wheel drive cars use a strut-type suspension that is composed of a strut, a hub assembly and a lower control arm affixed to the bottom of the strut. They all invariably use a rack and pinion type of steering. There is also an anti-sway bar connected to the frame with a set of links to the lower control arm. To properly diagnose these problems, the car must first be test driven and attention paid to the symptoms--when they occur and what type of surface they occur on. Attention should also be paid to the frequency of the occurrences.
Inspect the struts by using your knee on the bumper to bounce the car up and down. You should feel resistance to the movement of the car. When you cease to bounce the car, it should stop bouncing after one up and down vertical movement. If this is not the case, and during the test drive the car continues to bounce after going over bumps, the struts need replacement.
Lift the hood and look at the shock towers. This is where the strut attaches to the fenderwell or frame. This is easily recognizable by the round rubber piece on the fenderwell with a nut in the center of it. Its outside circumference has three or four studs coming up through the bottom side with nuts on the top. Look for cracks or tears in the rubber. Push up and down on the fender and watch the strut tower for any obvious looseness. If any of these conditions are present then the strut may be alright but the top of the strut (called a strut cap) which houses the bearing is bad and needs replacing. This can also cause a knocking or bumping noise when hitting bumps.
Jack the car up and place jack stands under the frame, letting the suspension hang. Grab the tire with both hands on the front and back of the tire and try to rock it back and forth as if it where turning to the left and right. Look for freeplay--the tire will move without any corresponding movement in the steering wheel. If there is freeplay then with one hand on the tire opposite side of the steering, grab the inner tie rod end and move the wheel. If the freeplay can be felt with no corresponding movement in the inner tie rod, the outer tie rod has failed and needs to be replaced. If there was movement in the inner tie rod, then the inner tie rod needs to be replaced.
Test for bad lower ball joints. Rock the wheel in and out. If there is play, have an assistant look at the lower ball joint as you rock the tire once more. If he can see obvious slop or freeplay in the joint, then the lower ball joint must be replaced. With a bad lower ball joint the car would show obvious uneven tire wear and have a tendency to shake the steering wheel when a bad bump is encountered. If there is freeplay, but it can't be seen in the lower ball joint, then the hub bearing is bad and needs replacing. This would not be as obvious in a test drive unless the bearings are bad enough to make a grinding noise.
Check the rack and pinion steering mounts under the car with a wrench to be sure they are tight. A loose rack and pinion can make a knocking or banging noise in a turn and can cause some steering problems in the form of jerking the steering wheel when turning.
Check the bushings and sway bar links for integrity. Make sure the rubber is in good shape and the links where the sway bar attaches to the lower control arm are present. These are a big cause of knocking and banging noises.
