Automotive How To: Changing Your Shock Absorbers

The first sign is at night and you notice something is wrong. Bumps hit harder, the car rocks when you stop at lights and your headlights illuminate things they never did before. The obvious diagnosis, your shock absorbers are worn out.

What we incorrectly call shocks in the United States, the rest of the world refers to as dampers. A properly operating shock system pads those bumps, turns and dips from being extremely obvious. A car with a bad shock system will hit the bottom or top of its limits of travel when it encounters one of these obstacles.

Inside your shock a piston forces oil through orifices and valves as the wheel moves up into the wheel well. When you hit the top of a bump, a different set of valves allows the oil to return, resisting the return force. As the miles pile on, the piston and its sealing rings wear down, allowing more fluid to pass. Also the springs, washers, and other parts of the piston wear out leaving your vehicle to take those bumps and dips at full force. When your vehicle starts responding in such a way, its time to replace your shocks. You should always replace both shocks at once or your car will have a different response on each side of the car.

Traditional shocks used two concentric tubes but no single-tube shocks are becoming more popular. The new type uses gas under inert pressure to prevent aeration of the fluid. Although slightly more expensive, the one cylinder model offers a better ride. Replacing the shock absorbers is a straightforward, albeit difficult, remove and replace procedure and all it takes is simple hand tools and elbow grease. If you car has coil-over struts you should take it to a professional to be fixed as any mistake can be dangerous.

Start by blocking the wheels to the front and rear and then loosen the lug nuts on whichever end of the car you're doing. Then jack the car up and secure it on stands, make certain the car is very secure and won't fall off, since you will be underneath it exerting excessive force. Next, remove the wheel. If you're changing a rear shock, it's usually only necessary to remove the hardware at the top and bottom. You may need to dive into the trunk or hatchback to remove the upper bolt, which might even mean removing or displacing some interior parts to access it. Loosen the top and bottom bolts. Before you remove them, however, hold up the suspension with a jack to keep it from drooping under the pressure from the spring. Check the bushings and the bump stop. Most shocks will come with fresh hardware, locknuts and rubber bushings, which I recommend replacing even if the old ones look fine.

The fronts generally represent a stiffer challenge. You'll probably need to remove a clip to free up the brake line. Late-model cars may have ABS sensor wiring that also needs to be dealt with. Work carefully and avoid damaging the brake line or wiring. Now you can jack up the suspension. If your vehicle makes its camber adjustment at the strut/shock bottom attachment bolts with integral eccentric washers, mark the index position of the bolts for later.
Remove the upper bolt from the shock's central damper rod and remove the shock from the vehicle. Important: Now you can check the upper bearing, if you have one, for wear. That may have been the source of that thumping noise you thought was a bad ball joint. On many front suspensions, the steering pivots in this bearing, and if it's worn, bad things will happen whenever you steer.

Now thoroughly inspect each bump stop, which may be either a pillow- or cone-shaped chunk of black rubber between the control arm and the frame, or perhaps a doughnut surrounding the damper rod hiding under a weather boot. If it's deteriorated, you must replace it to prevent damage to the new shock caused by overtravel. Oil leaking from the shock body or from the engine is usually tough on these rubber bumpers. If they are oily, out they go. While you're under there, check the ball joints, tie rod ends and CV joints as well.

You'll probably need to use the jack holding the suspension up to let you push the upper damper rod back into its bearing or bushing. And don't forget to torque the wheel lug nuts with a proper torque wrench. If your camber adjustments have been disturbed, you'll need to have the front end realigned.

Now, all that's left is to put the car back together and you have successfully changed your shock absorbers. Congratulations!