I did this on my last Z4 and noticed that the write up on here from Shipkiller was missing the photos. Decided to document my change on the current car.
Symptoms were a knock from nearside front, which when I investigated it was clear from visible cracking that the rubber in the top mount was failing.
Order list:
2x shock absorbers
2x top mounts
2x 18mm knuckle bolts (a must do according to Patriot66)
I decided to renew the rubber top and bottom pads being 18 years old, so two of each
Dust cover kit (2x plastic sleeves and 2x bump stops)
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Optional if showing signs of mushrooming, you can purchase reinforcing plates for the top of the suspension towers. As my top mounts showed no sign of the pins moving outwards I didn’t purchase.
Anyone looking to do this as DIY I’ll state the obvious: this is fairly high on the danger scale IF things go wrong, so judge for yourself if you can do this without risk. Biggest risks are jacking/supporting the car safely while working on it and the inherent risk when using spring compressors.
What follows is what I did- your call if you follow it or disagree.
Remove struts from car:
Loosen front wheel bolts
Jack the car up and support well, chock rears etc
Take wheels off
Some guides suggest unclipping the ABS, brake sensor and brake pipes from the seated positions on the strut, I didn’t need to do this as all came away from the bracket secured by the 18mm knuckle joint.
Loosen and remove the upper anti roll bar drop link- 16 or 17mm. If it spins pop a same size spanner behind it to stop the ball joint from spinning. Once off- move out of the way.
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I readied the following before trying to get the strut out of the joint:
A jack to place under the hub to control the downward movement of that area
A method of securing the hub once the strut is removed, to prevent any stress of the hub pulling on the cables/pipes
Something to support the hub from beneath
Then I started to free the strut from the knuckle joint. I found the best way (as I was replacing the strut) to use a hammer and gently tap the strut itself. I didn’t want to use any force on the hub (in case of damage to bearings) or by doing what Haynes manual says to open the knuckle by putting a screwdriver in the gap- for fear of cracking the metal.
Both sides slid down with a little encouragement, once lower freed up the 3 bolts per side were removed. Using the jack the assembly was lowered until the strut could be removed. Then, using the jack the hub was raised, an axle stand popped under to prevent strain, and the rope/webbing threaded and tied to support the hub. If it helps- I used the anti roll bar to tie the webbing around.
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Restating the obvious- this is the dangerous part, so only attempt in a safe manner. Alternatives are take the struts to a garage for them to use their hydraulic compressors etc.
Apply spring compressors to the spring. Once the tension is off the top and bottom, remove the 21mm bolt from the top of the strut. I found that this was very easy to achieve.
Taking the unit apart-
Remove the bolt, remove the top mount. Set aside all components and decide what you will be keeping or renewing from:
Top bolt
Top mount
Holding shim
Thick washer
Top rubber
Bottom rubber
Bump stop
Bellows/ sleeve
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Definitely the hardest and most complex part for me- what I describe is the way I did it. That doesn’t mean it’s the RIGHT way or the BEST way, it’s the way that worked for me.
I used 3 spring compressors in the following order- again if you choose to do this and cause damage or injury I accept no blame/responsibility; what I did in my back yard is only for info. The challenge with shorter springs is there is little coil to attach to. You can see the different types of compressor used- I call them type 1 and 2.
Reassembling the strut in the correct way: strut, bottom rubber, bump stop and tube, spring and top cap/rubber, I attached type 1 spring compressor as this:
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From that point, I attached a type 2 spring compressor here, and then continued to compress all in the relative safety of the top being bolted. Once I was happy that I had the suitable length on the top of the strut to attach the top mount, I popped the thick washer, shim and top mount on, bolted and torqued up as best as possible. Then backing off the spring compressors gently- a completed strut!
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Then- back on the car!
Retorquing:
Upper 3x13mm 24 Nm
Upper ARB drop link 65 Nm
Main strut bolt 64 Nm
Main knuckle bolt 81 Nm
After all done and you are happy with the set up, its advisable to get the steering alignment redone.
All in all, if you don’t get stuck it’s a simple enough job. I wouldn’t have done it without an impact wrench. Note I also binned the replacement sleeves which were plastic, in favour of the original rubber ones- which were much more robust (even after 18 years)
If anyone gets stuck in future feel free to drop me a line!
Cheers
Stuart
Credit as always to the helpers on here- Partiot66 (Si) and Tony!
