There's two things to check on the struts. Try to push the rubber boot up, then reach over the tire and hold your fingertip on top of the strut body so it touches the shaft, then push in and out on the tire. Feel for in and out movement on the shaft, (not up and down).
Look for oil leaking from the top of the strut body where the shaft comes out. There can be leakage without noise, but if there's noise, there's either going to be leakage too or the oil leaked out so long ago that it's dry now with caked-on mud.
The upper strut mounts can be real hard to diagnose unless the strut and spring are removed from the car and disassembled. This is probably one of the biggest reasons for revised estimates when having your struts replaced. Many mechanics now include the cost of new mounting plates in their original estimates so they're covered if those parts are needed. In some cases the large center nut can be removed to inspect the center hole of the mounting plate while the assembly is still on the car. If the center hole is enlarged due to rust, it will let the shaft wobble and move around. Clunking is the most common complaint but depending on the design of the suspension geometry, it can lead to the car pulling one way intermittently, the steering wheel shifting position slightly, or tire wear.
Besides that wear in the center hole, the bearing under the upper mounting plate can bind and cause a clunking sound and / or "memory steer". When the bearing binds, it makes it hard to turn the steering wheel. Those bearings support the weight of the front of the car on top of the spring which has to rotate with the steering system. The clunking sound only occurs when you're turning the steering wheel, and it's much worse when the car is standing still. The noise comes from the top of the spring refusing to turn so it winds up, then suddenly snaps free and rotates. You can identify that pretty easily by reaching over a front tire and holding your fingers on one of the upper coils on the spring, then have a helper slowly turn the steering wheel. You'll feel the spring develop tension, then pop free and turn. It's supposed to rotate freely. A little roughness is common.
Memory steer is when the upper mount sticks where it is after you turned a corner and the steering wheel stays there. You have to physically pull the wheel back to center. At its worst, that can be REAL irritating to drive and it can make the car hard to control.
Anti-sway bar bushings and links can cause clunks over bumps. A good clue is the noise will tend to stop when the steering wheel is off-center either way. Steering to one side causes one corner of the car to lift up. That puts the links and bushings under tension and prevents them from rattling. The difference is much easier to notice in a parking lot.
Worn ball joints can cause clunks. Sometimes they get noisier right after the car was jacked up. The suspension will hang down further than normal and redistribute the rust and mud still in the socket.
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Thursday, December 15th, 2011 AT 4:24 AM