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Rear Coil Spring Replacement
 
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Pelican Technical Article:

Rear Coil Spring Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$75 to $105

Talent:

*****

Tools:

Set of sockets, wrenches, screwdrivers,

Applicable Models:

BMW Z4 Convertible (2003-06)
BMW Z4 Coupe (2006)

Parts Required:

Rear coil spring

Hot Tip:

Replace coil springs as a pair

Performance Gain:

Car will ride well

Complementary Modification:

Replace rear shocks and shock mounts. Have vehicle aligned.

Shock absorbers and springs are the suspension components that maintain the mass of the vehicle suspended above the rolling gear: the wheels. Springs hold the weight up and shock absorbers dampen suspension movements so that passengers inside the vehicle experience a smooth ride.

The BMW Z4 is equipped with separate shocks absorbers and coil spring in the rear. For the front suspension, BMW utilizes a combined shock absorber and coil spring assembly referred to as a MacPherson strut.

The rear coil springs on Z4 models have a tendency to break at the last two lower turns of the spring. This is due to dirt and debris in the spring perch retaining moisture which causes the spring to rust then fracture. It's important to replace your coil springs in a pair to avoid an uneven suspension. Inspect the spring pads for wear and replace if necessary and always clean the spring perch area thoroughly.

There are a few ways to do the spring. I am going to illustrate how I replace them. Have a friend around when you do this repair. You may need someone to help lever a pry bar or install the new coil spring while you lever the trailing arm down.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Loosen rear wheel bolts but do not remove.

Raise rear of vehicle and support it safely on jack stands. See our tech article on vehicle jacking. When jacking, get vehicle as high as possible. You have to fit a hydraulic jack under the rear trailing arm.

Remove rear wheels.

The rear coil springs on Z4 models have a tendency to break at the last two lower turns of the spring (red arrow).
Figure 1

The rear coil springs on Z4 models have a tendency to break at the last two lower turns of the spring (red arrow). This is due to dirt and debris in the spring perch retaining moisture which causes the spring to rust then fracture. It's important to replace your coil springs in a pair to avoid an uneven suspension. Inspect the spring pads for wear and replace if necessary and always clean the spring perch area thoroughly.

Place a hydraulic jack under trailing arm.
Figure 2

Place a hydraulic jack under trailing arm. Inset shows the placement of the jack pad, directly under the trailing arm (red arrow).

Remove the rear shock (red arrow).
Figure 3

Remove the rear shock (red arrow). See our tech article on rear shock removing. You can remove only the lower shock mount bolt, removing the shock completely gives you more room to work. Remove the sway bar end lick mounting bolt. See our tech article on sway bar end link replacing.

Slowly lower hydraulic jack until spring tension on trailing arm is fully unloaded (red arrow).
Figure 4

Slowly lower hydraulic jack until spring tension on trailing arm is fully unloaded (red arrow).

Use a pry bar (red arrow) to lever the control arm down, hold it down.
Figure 5

Use a pry bar (red arrow) to lever the control arm down, hold it down. Then pull the bottom of the spring off the perch base and out of the control arm.

Pull the coil spring out of the top mounting point.
Figure 6

Pull the coil spring out of the top mounting point. Once the spring is past the mounting point, remove it from the vehicle. Have your assistant keep pressure on the control arm (red arrow) while you remove the spring.

Inspect upper and lower (red arrows) spring pads for wear or damage.
Figure 7

Inspect upper and lower (red arrows) spring pads for wear or damage. Replace if necessary. Clean spring perch area thoroughly. The colored stripes (blue arrows) can help identify the spring type when purchasing new springs.

Install upper and lower spring pads onto new coil spring.
Figure 8

Install upper and lower spring pads onto new coil spring. With both spring pads installed on new spring, install spring into vehicle, top of spring first. You may need help from a friend to pry trailing arm down in order to fit new coil spring into vehicle. I like to cover the top pad with soapy water or plain dish soap. This helps it slide in easier. If alone, this is the method I use to get the spring back in. I want you to keep in mind, this is not easy and the pry bar can slip, so you have to be prepared for that, and of course, keep your hands out of any area where they can be pinched. I put the bottom of the spring into the lower swing arm. Then place the end of my pry bar against the body and the rear sway bar bushing mount. Then lever the spring down while pushing it into the upper mount. You will have to lever down and toward the mount at the same time. This is why it is tricky. If you keep the pry bar seated against the body and the sway bar bushing mount, it shouldn't slide. Of course that isn't a guarantee. Lever the spring in until the mount align with the hole in the upper spring pad (red arrow). Once spring is properly installed in control arm, slowly raise suspension back into position. Install shock mounting fastener, then remove hydraulic jack from under training arm. Re-install sway bar mount to trailing arm. Rear shock and install rear wheel. After replacing your rear coil springs, it is a good idea to have your vehicle professionally aligned. This will prevent premature tire wear and ensure good handling.

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Page last updated: Wed 12/7/2016 03:02:18 AM