A Fresh Front Suspension is A Wonderful Thing - Failed Foam on Strut Assemblies

[crystalworks]

The wife's diesel had been having the infamous knocking over bumps for some time and we had been putting off servicing it because of other priorities. Well, the foam under the upper nut had finally disintegrated enough to where the center bushing on the upper strut mount tore away and allowed the strut to move from center on it. This was causing rubbing of the washer and the strut mount and a horrific squeal during any and all suspension movement. So now it moved up the priority scale.

For reference, this is a 2010 X5 xdrive35d with 155,000 miles. The tension struts and tie rods have been replaced at some point for sure, but everything else appeared original. I replaced everything except the tie rods.

Big thanks to SeanC and FunfDreisig for their thoughts/writeups here:

https://xoutpost.com/bmw-sav-forums/...build-diy.html

https://xoutpost.com/bmw-sav-forums/...ive-drive.html

Because those writeups are so good I am not going to do a full DIY or anything here. But, I did want to share some thoughts on my experience given that I was doing a full suspension refresh including the upper wishbones which I never hear anyone mention anything about. First, the torque values for everything are as follows:

1. Tension Strut to Axle Support = 74ft/lbs + 90* (Torque with suspension loaded)
2. Tension Strut to Swivel Bearing = 59ft/lbs
3. Lower Wishbone to Front Axle Carrier = 122ft/lbs (Torque with suspension loaded)
4. Lower Wishbone to Swivel Bearing = 59ft/lbs
5. Upper Wishbone to Body = 28ft/lbs + 90* (Torque after measuring the resting position of the wishbone being removed, basically new one has to be in the same position when tightened)
6. Upper Wishbone to Swivel Bearing = 41ft/lbs
7. Spring Strut Holder to Lower Wishbone = 122ft/lbs (Torque with suspension loaded)
8. Spring Strut Holder to Spring Strut Shock Absorber = 60ft/lbs

Here are a couple of pictures of the failure:





And the "pile-o-parts:"



Upper wishbones
Lower wishbones
Sway bar end links (not pictured, they were replaced very recently)
Tension struts/arms
Strut Mounts
All the foam parts (2 washers per side and a strut bumpstop)

Here is a shot with the strut assembly removed. At this point it was time to remove the fender liner to get at the top wishbone mount bolt/nut. Great design BMW... I'm glad they don't have to get serviced very often. Honestly, I probably could have left the originals in there and been fine, but when I do a front suspension I tend to do the whole thing at once. I hate doing parts piecemeal and having to go back in again after the next weak suspension component gives up the ghost.



Strut assembly removed. Mark all your orientations of the spring, mount, etc. I had to rotate the spring upper pad in my new mounts to match the old ones. There are 2 possible orientations. As long as you match everything from the original you will be fine. There are some blue indications under all that road dirt to guide you as well but I made new marks adjacent to those on all the new parts as well. PS, if using a spring compressor like the one pictured... try to grab 4 coils at least as the 3 shown below is a little difficult to get enough compression to relieve the strut enough to get the top nut/washer/foam pad back on. On the passenger side I grabbed 4 coils and the job was easier for sure.



Here's a shot of the mounts for the upper wishbone after fender liner removal (BTW, if anyone knows how to remove the electrical box for the brake pad and wheel speed sensor let me know... I could NOT get it off for fear of destroying it). Couple of notes on these. On the driver's side loosen the power steering reservoir and the coolant reservoir up top to give yourself an added ~inch of clearance to access the nut. On the passenger's side loosen the ABS unit to gain an extra few CRUCIAL mm's of clearance. It only takes removing 2 13mm bolts from the bottom of it's mount. The brake lines have enough flex to give you clearance to access the nut on the upper wishbone. Oh yeah, torque this down before you put your strut assembly back in. Will make your life much easier. Ask me how I know.



While doing this job I had to remove the rear panels that contain the infamous drains which everyone talks about but no one can take a picture of because of their location. Well, here's a full naked shot of the clogged driver's side drain. I removed mine entirely. Accessing them is a PITA and now I don't ever have to worry about a clog. Things are fairly protected under there so I don't have any worries about ramifications of their removal.



And finally, a shot of the new upper wishbones installed with the rebuilt strut assembly. Overall this job is not too difficult but it is kind of tedious. Took about 10 hours total over 2 days. Parts cost was about $700 including the 27mm 12pt socket to get the tension arm swivel bearings and the lower wishbone swivel bearings off. I'm not sure how much this would cost to have done at an indy, but I'd guess in the $1500 - $2000 range. I won't even guess at the dealer costs...



Hope this info helps someone out. The suspension feels amazing now as is typical after a full front suspension refresh on a BMW. My wife immediately noticed and is very pleased with the results. Happy wife, happy life right?

[Entropy]

Very helpful, thank you! I have new parts to rebuild the strut coming in. I’m at 111k miles. How worn out were your wishbones? I’m on the fence as to whether or not I should replace them. I’ve already done lower control arms, end links, and tension rod bushings.

[crystalworks]

Originally Posted by Entropy

Very helpful, thank you! I have new parts to rebuild the strut coming in. I’m at 111k miles. How worn out were your wishbones? I’m on the fence as to whether or not I should replace them. I’ve already done lower control arms, end links, and tension rod bushings.

They weren't terrible. The bushings were in decent shape. Didn't notice any crazy cracking or tearing. The ball joint/swivel joint was definitely looser than the new one. But again, nothing crazy. I'm guessing these don't typically cause anyone noise/NVH problems and is why they almost never get serviced. I am of the mindset that when I am in there... it's all getting done. I'm still wishing I would have done the sway bar bushings even though they looked fine.

[josiahg52]

This is something I know I need to do. I'm coming up on 140k miles. So far there are no weird sounds and it still rides well enough but I bet it could be better. I'm thinking OE components and Bilstein struts.