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How to Replace Struts and Shock Absorbers in Your Car

Shock absorbers.
Shock absorbers. | Source

Strut and shock absorber replacement is not a common repair. The original components usually keep working beyond the 100,000 miles mark. But they do eventually need service, due to wear or failure.

Fortunately, you can do this repair at home on many vehicle models. For the most part, you only need a set of common tools; however, on some models you need to use special tools, like a spring compressor, to remove a strut assembly from the vehicle, but this is not common, most assemblies come out as a single unit.

Still, you'll need to use the compressor if you do want to replace a cartridge (absorber) or coil in a strut assembly yourself, if that's what you need. We'll get to that later, though.

This guide will give you a step-by-step outline of the repair process, so you have an idea what your repair project takes from start to finish. We don't deal with electronic shock absorber systems, though.

So, let's start with a brief explanation about how the struts or shock absorbers in your car work.

Index
I. How a Strut and Shock Absorber Work
II. Replacing Struts and Shock Absorbers
A) Strut Replacement
B) Shock Absorber Replacement
WARNING - Removing a Shock Absorber
III. Replacing the Shock Absorber (Cartridge) in a Strut Assembly
IV. What You Need to Know When Reinstalling a Strut or Shock Absorber
Top Five Tips When Replacing Struts or Shock Absorbers in Your Car
After thousands of miles a shock absorber may wear out or break.
After thousands of miles a shock absorber may wear out or break. | Source

I. How a Strut and Shock Absorber Work

Next to each wheel assembly, you can find some kind of spring (leaf, coil or air type) to prevent the car body—and passengers in it—from taking a direct 'hit' from road dips and bumps.

However, every time this spring compresses, it enters into a decreasing cycle of compressions and decompressions. So driving a vehicle fit with nothing more than a set of springs would result in a less than a comfortable ride.

Thus, your vehicle may use struts or shock absorbers, or a combination of both, to dampen the spring bouncing cycle for a smoother ride.

In general terms, a standard shock absorber consists of an oil-filled cylinder with a rod connected to an internal piston. A set of valves allow the oil to flow slowly through the piston in either direction as needed.

At the lower end, a shock absorber connects to the control arm or axle; a strut connects to the steering knuckle, which holds the wheel assembly. On the upper end, the shock absorber or strut connects to the car body.

A strut assembly consists of a mounting base, cartridge (shock absorber unit), coil or spring and related assembling and mounting hardware. The shock absorber itself comes under different configurations, even computerized designs, for better efficiency and finer control.

In short, as a spring helps isolate a car body from direct road 'impact', the shock absorber helps to dampen spring movement. And, although both shock absorbers and struts do the same job, a strut also works as an extension of the suspension functionality in your car.

You can find a shock absorber behind the wheel assembly.
You can find a shock absorber behind the wheel assembly. | Source

II. Replacing Struts and Shock Absorbers

Now that you know the difference between a shock absorber and a strut assembly and their functionality, it's time to replace them.

1. Park your vehicle on a level surface and open the hood. Place the transmission in Park (automatic) or in gear (manual) and apply the emergency brakes.

2. If your vehicle has Automatic Ride Control (ARC), turn off the air suspension switch before jacking the vehicle.

3. Loosen the wheel lug nuts on the side with the shock absorber you want to replace.

4. Lift the tire off the ground with a floor jack and safely support the vehicle with a jack stand.

5. Finish removing the wheel lugs and tire.

A) Strut Replacement

1. Working from the engine compartment, remove the three upper mounting nuts holding the strut assembly to the body.

2. On some vehicle models, you need to disconnect the tie-rod end from the lower part of the strut-steering knuckle assembly.

  • For this, you might need a puller to disconnect the tie-rod from the steering knuckle.
  • On some other models, you may need to remove the brake caliper, brake disc and even the hub assembly, before you can remove the strut assembly.
  • Also, if your car has the ARC system, you'll need to disconnect the electrical connectors, air line, and sensor from the assembly.

3. Then, disconnect any harness, line or component attached to the strut assembly. Consult your vehicle repair manual, if necessary.

4. When rust won't let you turn the mounting bolts, apply penetrating oil to the threads.

NOTE: In some models, you need to first compress the coil spring before you begin to loosen the strut mounting bolts. Consult your vehicle service manual, if necessary.

5. Begin loosening the nuts on the two lower mounting bolts that hold the strut to the steering knuckle, until the nuts are flushed with the lower end of the bolts.

6. Using a hammer, carefully push the mounting bolts out, remove the nuts off the mounting bolts and finish removing the bolts.

7. Carefully pull the strut assembly flange off the steering knuckle.

  • If you have difficulty separating the strut mounting flange from the steering knuckle use a rubber mallet or wood block to tap on the steering knuckle to help separate the strut from it.
  • On other models you may need to spread the steering knuckle and strut joint using a pry bar to separate the components.

8. Once you have detached the strut from the steering knuckle, use a piece of wire to secure the steering knuckle to the suspension to keep the knuckle from swinging.

9. Remove the strut assembly off the vehicle.


B) Shock Absorber Replacement

1. Working from the engine compartment, loosen the upper mounting nut holding the shock absorber to the body. On some models, you access the upper mounting bolt from under the car after lifting and safely securing the vehicle.

  • If the rod in the shock turns when trying to remove the upper mounting nut, try holding the rod in place with a pair of vise-grip pliers from under the vehicle.

2. Support the lower part of the shock absorber (usually the control arm or axle) with the floor jack.

3. Apply penetrating oil to the bolts to make it easier to remove, if necessary.

4. Loosen and remove the bottom mounting bolt holding the shock absorber in place.

5. Remove the upper mounting bolt and slowly lower the floor jack a few inches, if necessary, to work the shock out of the vehicle. Leave the jack in place to support the axle or control arm.

A strut assembly with coil, mounting base and cartridge.
A strut assembly with coil, mounting base and cartridge. | Source

WARNING - Removing a Shock Absorber

In some applications, you need to support the axle or control arm (usually with a jack) where the shock connects to before actually removing the shock mounting bolt. This will prevent the shock from shooting downward after removing the mounting bolt, which can cause a serious accident.

After removing the shock absorber, leave a jack or jack stand supporting the control arm or axle in place. Consult your repair manual, if necessary.

Worn strut upper mount.
Worn strut upper mount. | Source

III. Replacing the Shock Absorber (Cartridge) in a Strut Assembly

Once you have the strut assembly out of the vehicle, you can replace the cartridge (shock absorber) yourself in your shop. You can follow these guidelines to disassemble the unit.

1. First, a couple of important things you need to know:

  • The spring in a strut is assembled under high pressure.
  • Use a quality spring compressor to disassemble the strut. Using a low quality compressor (or using a quality one incorrectly) can lead to a serious or fatal accident.

2. You may loan a spring compressor from your local auto parts store.

3. Use a vise to hold the strut in position while you work on it.

4. Install the spring compressor on the coil and gradually begin to compress it until the upper strut seat is loose.

5. Unscrew the lock-nut holding the top of the assembly.

6. Remove the top of the assembly, taking note of the order of the components.

7. Replace the old cartridge with the new one and reassemble the strut.

A couple of options, depending on your budget: You can take the old strut assembly to a shop and have them replace the cartridge for you. Or, you can buy a strut assembly ready to install in your vehicle. This way you replace the coil and old hardware at the same time.

IV. What You Need to Know When Reinstalling a Strut or Shock Absorber

Follow the same procedure you did to remove the strut or shock in reverse order, keeping in mind the next guidelines.

1. Place the strut assembly or shock absorber in position and install the mounting bolts finger tight.

2. Torque all mounting bolts to specifications. Consult your vehicle repair manual for this.

3. When installing the tie-rod to the steering knuckle, tighten and torque the mounting nut to specification.

4. Place the tire assembly in its mounting position, back up the assembly against the wheel, and install the lug nuts finger tight first.

5. Lower the vehicle and torque the lug nuts gradually in a crisscross pattern. Look up the torque specification in your repair manual or car owner's manual.

6. Tighten the upper strut assembly nuts to specification.

7. Finally, if you replaced the front struts or shocks, have the front wheels aligned.

Top Five Tips When Replacing Struts or Shock Absorbers in Your Car

1. When buying your new shock or strut, buy a quality replacement; otherwise, you may find yourself under the car replacing the just installed unit after a few miles of use.

2. Always replace struts or shock absorbers in pairs (front or rear axle) to keep the suspension balanced, unless you need to replace a fairly new faulty unit.

3. If you are replacing old struts, you might want to consider replacing the whole assembly. You'll have a new coil and cartridge already assembled ready for installation.

4. Even if you are replacing both front or rear struts or shocks, always replace one unit at a time, since the shocks may be helping to keep suspension components in place. You'll avoid potential damage to other parts.

5. When replacing a rear shock, you may need to look for an access cover in the trunk, under the trim or the back of your vehicle.

When doing a strut or shock absorber replacement, a guide can only give you a general idea of the actual process. The specific steps vary among different makes and models, though. Although for some vehicle models this guide will be all you need, I recommend you consult your vehicle repair manual, you'll need the mounting bolts torque specifications during the installation process for your particular application.

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