[Gile89]

I tried to make this post short, but its not at all..Just a little warning

After having a clunking noise coming from the rear of my suspension, I decided to replace the rear shocks on my car (1996 S600).I was lucky to come across a S500 with ADS at a junkyard during my vacation, so I had to get up early, buy some tools, drive 45min and remove them and send them back home so I had a spare to play around. I saw them new online in stock for about $450-$550. Long story short and after making about 10 orders with various vendors and various part numbers (1403209913, 1403209613, 1403208913, etc), a lot of calls, I found out that they do not exist anymore and are replaced by part number 320-96-13-26 with a new price tag of about $1000 to $1200. Once I found that out, I definitely decided to replace the bottom bushings and top mount/absorber on mine own and not pay over $2000 for new ones.

I have seen a thread where some people successfully replaced bottom bushing with Lemforder control arm bushings PN# 31121124622. This requires cutting a metal jacket and shaving the rubber so I tried to find a different solution. I decided to go with a polyurethane bushing for bottom of the shock.

After a lot of research, the best option I found was this bushing (PF99-104) from PowerflexUsa that has outer diameter of 35mm and its $28, with full dimensions shown below.

Given that the length of a bushing housing at the bottom of my stock shock is about 31mm-32mm I had to cut “G” part of the Powerflex bushing to be about 16mm since I need 2 on each side (16x2=32mm). The lip “H” is 7mm so that gives me total length of the entire bushing once pressed in of about 46mm (G-32 + H-14), if I cut it where lip “H” sits exactly on the outer edge of the bushing housing. You can leave “G” part little longer and have exact length of 52mm (length of the inside sleeve) but I didn’t do that, I left about 2-3mm left on each side and used a washer.

Talking about the metal sleeve inside of the bushing, that was another problem since the sleeve that comes with the bushing PF99-104 is meant for an 8mm bolt and mine is 12mm, and its also much longer than 52mm. I had to find a new sleeve that’s 52mm long (to match stock sleeve length), with outside diameter of 16mm and inside diameter of 12mm to fit inside powerflex bushing and to accommodate the stock bolt. I couldn’t find it anywhere so I had to custom order it and have it made from somebody on ebay. It costed me $18 per sleeve.

Left is what was inside of the stock shock bushing, and to the right is a sleeve I ordered.

Ok, so now how I did it…

I first I pressed out the stock bushing with a 12ton press with ease, using a 1 ½ socket:

I just pushed against the inner sleeve an it popped out on the other side, it popped twice, first time to break the metal seal/lip and the second time when it was totally free. Then I had to flip it to the other side, and pop the other side since metal seal/lip was still there and some of the bushing was still there…

First side successfully popped…

Other side with the lip/seal and some of the bushing left inside.

Like I said, I just re inserted original metal sleeve from the other side and pushed through the metal seal/lip and got everything out.
Other side being popped like this:

 

[Gile89]

So here is what was pressed out and you can see the metal seal/lips I am talking about next to everything else that was pushed out:

So now that old bushing was out I had to get the new Polyurethane bushing in. I also bought another bushing with 32mm diameter but that one was too loose and it makes sense since inside diameter of the stock bottom shock housing is more like 33mm.

I also measured the stock metal sleeve that was inside and it was about the same:

Bushing, PF99-104 has 35mm outer diameter and was slightly too big. I think it could have been pressed in but I did not want to risk it so I trimmed the diameter down just about 1mm or so and it was a good snug fit. I did find someone with lathe locally to trim it in minutes but if I didn’t I was going to try with the sandpaper (I am sure you can use a Dremel too). Also, inside of the stock shock bushing housing can be slightly sanded down/cleaned up and that would help gain some more space if you are doing it without a lathe.

PF99-104 bushing diameter:

Below is how much the “G” part or the length was cut or shortened by (I did it with lathe but I am sure it can be done with razor, saw, or similar)

Below is how it looks finally pressed in (I did it with a 12ton press and it was easy). There is about 2mm of sleeve sticking out but I don’t think it’s a big deal even if it moves. I did use the M16 washer just in case too. This is also where you can originally cut the bushing little less and have it 52mm long to match the metal sleeve exactly, but I wanted to have the “H” lip of the bushing against the edge of the shock and wanted a few millimeters of room in case it’s a tight fit. It’s easier for me to add a washer than to take it all out and have to cut it again. If I had my own lathe sure, but I don’t, and did not want to risk it and have to make another trip for an additional 1mm cut.

Now that the bottom bushing is done, I went for the top mount/absorber.

I read that to take the top mount/absorber (1403200944) off you need to heat the hell out of it. Oh well I did use the small torch and heated it pretty well, I thought, and when I tried to unscrew it, I heard something pop and the mount just started spinning. I tried heating it waay more after that but the mount would just spin. So I had to cut through it. I had someone cut through it (Same person with lathe locally) and what I realized is that I did not heat it nearly enough so something inside the mount just broke and was spinning but the stud on the shock and the mount were not spinning.

Once it was cut through, I was left with the rubber and some metal, once we heated that part with a huge torch and used some big pliers, it started unscrewing fairly easy. I still went very slow with a back-and-forth motion just to be safe but it was easy. So, if you are doing this make sure you really torch it and all you need is the bottom stud to heat up so Loctite can give in.

 

[Gile89]

After this, I just put some red Loctite on and screwed the new mounts/absorbers on, waited 24h for Loctite to fully cure and that was it.

Final product:

My original plan was to replace shocks and springs only, but once I took the lower control arm off in the rear, I saw that the knuckle/spindle bushing was shot as well. So, I ordered new ones and had to install them.

After struggling a little to take the first one out, putting the new one in and doing the other side was a breeze and that’s probably because car was not rusted and my home made tool (~$30) worked great.

I went to Home Depot with the new knuckle bushing in search of parts for my tool so I ended up buying this:

1 x 6in Grade 8 bolt ($3)
Couple 1/2in washers
Couple 5/16in washers
4 x 1/2in grade 8 nuts ($2)
1x 1 1/2 inch galvanized cap ($7)
1x1-1/2 in. Rigid Conduit Nipple ($4)
1 x 1-1/2 in. Galvanized Iron Plug ($7.50)
1ft ½ threaded rod ($2.50)

I had to drill a 1/2in hole in the cap and the plug for the bolt and rod to go through. To get the bushing out I used 15/16in half an inch socket and it worked perfect, I pressed it out into conduit nipple that was just a perfect size to receive the bushing. And to drive the new bushing in I used galvanized iron plug, which fit perfectly around the edge of the new bushing without damaging the rubber, I was pretty excited when I found it at the store and how well it fit:

Extracting a bushing (used 6in bolt). Little tip is to make sure you align receiver well on the opening so the edge does not overlap the opening which would prevent the bushing entering it as its being pushed put:

You can see on the picture below the size of the bushing getting into a receiver and why you need to make sure its align properly as there is not too much wiggle room:

Putting a new bushing in (used 1ft rod). If I had 7in bolt it would work great, but they didn’t have it at the store so I got a 1ft rod.

This is how bushing sits inside of 1 x 1-1/2 in. Galvanized Iron Plug to drive it in:

Pictures of the set up while on the car, pressing a new bushing in:

New bushing is in, I think it could have gone little more in, maybe 1mm or so but my driver (Galvanized Iron Plug) was not able to go further in, but it should be fine I think:

Old vs new bushing:

 

[Gile89]

Drilled holes, make sure they are centered (I was little off on the one to the left but it worked)

Not sure if it matters to anyone but I did take a lot of measurements so here are some, it might help you when looking for a perfect set up, at least it did help me:



New bushing diameter (40.12mm), old one was close to 40mm:

Knuckle space for the bushing (39.30mm), it was hard to measure it so I might be slightly off but I sanded it down and cleaned it up later so that might have gotten me some extra space:

After the bushings were done, I replaced the springs and Mercedes spring compressors tool made it suuuper easy but also so scary at the same time, just make sure that top plate of the compressor is not placed higher than the 3rd coil since you won’t be able to release the shock compressor once decompressed due to it being too high (don’t ask me how I know it).

For springs it was interesting that my new springs were taller than old springs, but when measured with the spring pads on, both were the same height. My old springs had a spring pad 140-325-04-84 which is the thickest one. I followed below instructions and got the pads 140-325-01-84 and springs 140-324-19-04 since my springs came with blue mark.

With the pad:

With no pads:

That was it, I went for a 5–10-minute ride, after refiling hydraulic fluid, and everything seemed just fine, and no more rear end noise. I will try to report back much later on how shock bushings are holding and everything else.

I hope it helps someone in the future since I did not want to pay over a $1000 for a single shock and get charger around $1000 for knuckle bushing replacement (highest quote I got was $1400+ for knuckle bushing replacement!) which would total in well over $3000 easily just for those two. In my case bushing for the bottom of the shock was $28 each, metal sleeves were $18 each, top mount was $97 each, so that’s ~$286 to fix both shocks and I do not anticipate Polyurethane bushings going bad before the shocks go out since Polyurethane is so durable.

I tried not to make it too long but it’s hard since I took so many pictures and went through so many steps to get all this done. If I missed something let me know and I will try to clarify it.

 

[Aerosurfer]

Great work! But why would you use red locktite on the upper shock mounts? I was led to believe they seize due to dissimilar metals (steel and aluminum) but for the next time, whenever that may be, it will still be a bear to remove.

I have removed 2 differend sets of the old ones and cutting off the outter shell and heating the inner is the easiest way. Its messy for sure

 

[Gile89]

I read that factory used red Loctite which is why its impossible to remove it w/o heating it so much, so I did too, but it could be just different metals like you said. I cleaned up the threads before putting new ones on and was not 100% sure I saw Loctite residue on it (maybe it stayed inside of the old mount thread). I did think it might be an overkill so I literally used a drop. I probably would not use it next time (since I will do this all over again on my spare/original set that came off the car). Maybe I would use the blue Loctite this time just in case. I will definitely look for it more closely next time I take off those top mounts.

 

[Aerosurfer]

You have done magnificent work! The locktite comment was just an observation. Hopefully the fabricated lower bushings last and are indeed a viable solution!

 

[daidnik]

Desperation breeds creativity.

Without at least occasional bouts of desperation, engineering would never have progressed as it has.

Excellent resourcefulness and you saved yourself at least $800 minimun.

 

[Marcin T]

Great work! Thanks for sharing. Does anyone know if replacing original mounts with rubber or polyurethane has any side effects? Is there a risk of leaks or damaging the struts? Anyone use this solution for longer time and can share the experience?

 

[luschka]

Excellent write up. I guess I am lucky in that both of the upper shock mounts I removed have been pretty easy. I just clamped the shock in the vise (grabbing the cast piece where the SLS line comes off) and turned the upper mount with Channel lock 440 pliers.
However I recommend against ever re-using the upper mounts as I think the torque required to disassemble these disrupts the rubber inside. I re-used one, and now I have the slight clunk so will have to spend the $100 and get in there again. It is also possible but annoying to change the top mount without opening the SLS hoses, assuming the top mount isn't seized. There's just barely enough room to sneak the shock out.

Anyway, thanks for the write up. I like this better than cutting down a soft rubber BMW control arm bushing. Before resorting to replacing the lower heim joint, I am planning using an external boot to keep the original heim joints out of the elements. I bought aerosurfer's good used rear shocks, and even though they are in great condition the boots are torn. Commercial heim joint boots are far too small, but I've got some tennis balls I may cut up to slip over the ends and fill with grease, probably via syringe.

PS: I as well have spent a good amount of time lurking on the board looking for solutions for the rear shock mount. Here's my plan C...

 

[Marcin T]

I will share my experience. I had a problem with a slight knocking in the rear shock absorbers, I replaced the lower mounts, but the problem persisted. I sent the shock absorbers to a remanufacturing company and it turned out that the rubber bumpers crumbled and bits went under the shock leg seal. This caused a slight air intake and knocking. After replacing the internal seals, it is quiet.

 

[Gile89]

I will share my experience. I had a problem with a slight knocking in the rear shock absorbers, I replaced the lower mounts, but the problem persisted. I sent the shock absorbers to a remanufacturing company and it turned out that the rubber bumpers crumbled and bits went under the shock leg seal. This caused a slight air intake and knocking. After replacing the internal seals, it is quiet.

Interesting, it would be hard to find here in US someone who would reman these. I tried few places and they thought I was crazy, they tell me they don't work on those hydraulic shocks. But I am glad you fixed your issue.

 

[rbelton]

Excellent write up, thank you for sharing this detailed info. Has anyone tried replacing the bottom bushing by threading off the whole piece? I came across this product:

Mercedes Benz S-Class W140 1992-1998 OE New Suspension Rear Left/ Right Shock Absorber Bushing (1403209313)

Find amazing deals on Mercedes Benz S-Class W140 1992-1998 OE New Suspension Rear Left/ Right Shock Absorber Bushing. Order today and receive Fast Delivery and Discounted Prices!

rebuildmastertech.com

 

[Gile89]

That is an interesting find. I did contact those guys to see if they include rebuilding top and bottom bushings in their $500service for rebuild of our shock, but they said they don’t, they just replace internal seals so I passed on them. I don’t remember seeing this part back then in June of 2022. It must be new.

It looks like they are using the same bushing we use in our cars for knuckle/spindle bushing In the rear, which is a very common mercedes bushing (Febi Bilstein 21174 or OEM part #2043520027). This is little different than stock heim joint and bushing that’s in there.

I have 2 spare rear shocks for my s600 and I am almost tempted to try and test the part you posed and install it. It looks like in this thread (#8 post) someone took the bottom shock apart and you can see where the part you posted would screw on. Pretty cool if that would work,but taking apart the bottom bushing/heim joint of the shock means cutting spot welds and then welding it back together or using JB Weld like the OP did when he put the shock back together.

Pic is from the #8 post I referenced:

 

[rbelton]

Great follow up, Gile. I hadn't realized that. You're right, looking closer now, it does in fact appear that the rear joint is the same (or very close) to what this company is pressing into the lower mount. Here's FCP's link to it:

Mercedes Bushing - Febi Bilstein 2043520027

Mercedes Bushing - Febi Bilstein 2043520027

www.fcpeuro.com

So I wonder where the thread-on part is from. Or custom made.

To clarify; to install this $99 bushing from Rebuild Masters, no cutting of a weld is required. That part simply threads off/on.

What I think you're saying is, to attempt to use part #2043520027 in the original lower mount, that is what would necessitate cutting of the weld of the original joint in order to salvage the carrier for the bushing. Is that correct?

Perhaps I'll order up that bushing (#2043520027) and measure its dimensions with a caliper.

 

[luschka]

Perhaps I'll order up that bushing (#2043520027) and measure its dimensions with a caliper.

https://partsfinder.bilsteingroup.com/en/article/febi/21174

• Inner diameter [mm]: 15
• Height [mm]: 48
• Weight [kg]: 0,222
• Diameter [mm]: 40

EDIT:
Per my measurements on this image I made months ago, the mounting bolt hole is 12mm on the original part, this bushing reports a 15mm bolt hole.

 

[Gile89]

To clarify; to install this $99 bushing from Rebuild Masters, no cutting of a weld is required. That part simply threads off/on.

What I think you're saying is, to attempt to use part #2043520027 in the original lower mount, that is what would necessitate cutting of the weld of the original joint in order to salvage the carrier for the bushing. Is that correct?

Are you sure about this, person who took it apart said "I used a sawzall to seperate the cup from the plate it is spot welded to". That's what I was referring to. You can read the post #8 in the link I provided previously.

If it just threads off that would be much easier and doable. I might go ahead and inspects my spare shocks that I have and see if I feel like tying to take it apart and install the $99 part you posted.

 

[rbelton]

Ok I re-read that thread you linked, post #8. It makes sense now. It looks like the $99 part does "just thread on". However, in order to loosen it, you need to clamp the strut rod in a vise or with vice-grips to stop it from spinning. That is why cutting the weld and moving the metal part out of the way is necessary.

You can see in the photo there is a collar right above the $99 bushing piece. It looks like the strut rod goes through it. So, if you were to attempt to just clamp that and then unscrew the bushing, that collar may just spin. Just making assumptions based on the images, I don't have a shock in hand (they're on my car still).

Hope this clarifies any confusion (mine included).

 

[rbelton]

I have an interesting observation to share, perhaps someone can offer some insight. It has dipped to 0 degrees F outside this weekend. My passenger rear SLS rear shock that has been creaking back there is no longer making ANY noise. Perfectly quiet on this frigid day. It will begin to squeak again once temperatures warm up above 32 most likely. I've noticed that on very cold days below 32 there is little or NO noise.

I suspect the bottom mounting rubber bushing is the cause for the creaking, but haven't verified. Can any guru's confirm what the diagnosis might be if they are familiar with this cold weather phenomenon? Grateful.

 

[MAVA]

Gile,

Awesome thread, but I like your approach with the violet bushings... NZ.. post with the BMW bushings is also an elegant approach.

Thank you for sharing!

Martin