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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:

$

Talent:

*****

Tools:

Set of sockets, wrenches, screwdrivers,

Applicable Models:

BMW Z3 (1996-02)

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 Z3 is equipped with separate shocks absorbers and coil springs 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 Z3 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 and causing 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 them 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.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

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 you're 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. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Loosen the rear wheel bolts but do not remove them.

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

Remove the rear wheels.

Place a hydraulic jack under the trailing arm.

Working at back of trailing arm, remove the 18mm rear shock mounting fastener (green arrow).
Figure 1

Working at back of trailing arm, remove the 18mm rear shock mounting fastener (green arrow).

Working at back of trailing arm, remove the13mm sway bar bushing mounting bracket fastener (green arrow).
Figure 2

Working at back of trailing arm, remove the13mm sway bar bushing mounting bracket fastener (green arrow). Slowly lower hydraulic jack until spring tension on trailing arm is fully unloaded.

Use a pry bar to lever the coil spring out of the top mounting point.
Figure 3

Use a pry bar to lever the coil spring out of the top mounting point. Once the spring is past the mounting point, remove it from the vehicle. Unlike other BMW models, Z3s coil spring does not drop out when the suspension is unloaded. With the suspension all the way extended, the coil spring has to be compressed. The good news it is a light weight coil spring and can be levered out quite easily. Now be careful when doing this. Use only the pry bar to remove it and keep your hands and feet away from the spring. You wouldn't want to get pinched by it if your tools slips.

Inspect upper (yellow arrow) and lower (green arrow) spring pads for wear or damage.
Figure 4

Inspect upper (yellow arrow) and lower (green arrow) spring pads for wear or damage. Replace if necessary. Clean spring perch area thoroughly.

If bottom turn of coil spring is stuck on lower spring pad, remove it by prying off with a screwdriver or pry bar.
Figure 5

If bottom turn of coil spring is stuck on lower spring pad, remove it by prying off with a screwdriver or pry bar.

Install upper (yellow arrow) and lower (green arrow) spring pads onto new coil spring.
Figure 6

Install upper (yellow arrow) and lower (green arrow) spring pads onto new coil spring.

With both spring pads installed on new spring, install spring into vehicle, bottom of spring first.
Figure 7

With both spring pads installed on new spring, install spring into vehicle, bottom 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. You will have to compress the spring a bit because the suspension doesn't drop down far enough.

If alone, this is the method I use to get the spring back in.
Figure 8

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 (yellow arrow) align with the hole in the upper spring pad (green arrow). Once spring is properly installed in trailing 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 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 03:07:05 AM