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2006 SLK280
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1,236 Posts
Discussion Starter · #1 ·
After almost 15 years and 80,000 miles the front shocks on my car were worn out. The front end bounced up and down like a trampoline over speed bumps and bottomed out over railroad tracks. I bought a new set of OE style front shocks from Bilstein; I switched to Bilsteins on the rear last year and have been happy with their performance. I also elected to replace the front sway bar links, the stop bumper and the mount at the top of the shock. Essentially all of the rubber parts from the sway bar frame were replaced, which is worth the extra money if you are doing the work of replacing the shocks, IMO.

A couple years ago mllcb42 posted a great tutorial on getting the shocks out of the car. That thread was very helpful in getting the shock out. Due to the lack of small independent MB mechanics around here, I decided to do an extra step of DIY and mount the springs on the new shocks myself.

Note that I am not a mechanic, nor is what follows advice on how to work on your car. This thread is only to document how I was able to complete the job on my 2006 SLK280. Any similar or related work is done at your own risk, there is no assurance of safety, completeness or adequacy of the information documented in this thread. Shocks store a large amount of energy when compressed and are inherently risky to work on.

Materials and tools I used for the job:
Plate Style Spring Compressor
New Shocks
New Shock Mounts
21 and 22 mm Open Sockets
7mm Allen Wrench

I decided to reuse the existing springs for several reasons: I still had the original springs on the rear, I was fine with ride height on the car and they were free from cracks, corrosion, etc. Bilstein does make a replacement spring, but it is intended to replace 'red and white' marked springs. Mine were marked 'blue and white' so your results may vary with an aftermarket spring.
 

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2006 SLK280
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Discussion Starter · #2 ·
Once the old shock is out of the car, I mounted the spring compressor. The shock was covered in oil, so I assume it started leaking and stopped damping properly. I attached one plate over the bottom 'basket' of the shock and the other as far up on the spring as it would go without interfering with the mount at the top of the shock:

It was important to note where the top plate mounted to the spring for reassembly. If you put the compressor too high up on the spring, it will get caught between the spring and the top mount on reassembly and you will have to take the shock apart again. Mount it too low and the spring will not compress enough to remove/install the top mount.


After the spring is compressed, I checked it had pulled away from the top mount:

It's not easy to see in the picture, but there was a gap between the spring and the mount. This is actually very similar to the WIS instructions for compressing the spring. The official MB tool has a special plate for the shock basket, but the tongue of the plate on compressor off Amazon seemed to fit well enough into the groove in the basket.


I attached the open socket to a breaker bar to remove the nut on the top of the strut. My original struts had a 21 mm nut on top. The replacement Bilstein shocks have a 22 mm nut. First, I held the nut while turning the mount itself to break the mount away from the shaft:



Then, holding the shaft with the Allen wrench, I broke the nut loose from the shaft and removed it:
 

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2006 SLK280
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1,236 Posts
Discussion Starter · #3 ·
Then I removed the top mount from the shaft, decompressed the spring and removed the spring from the shock:

The spring becomes much longer when decompressed.


I had to reuse the lower spring mount, which is a small strip of rubber that sits in the shock basket:

I would have preferred to install a new one, but the Bilstein shock doesn't come with one and the part is not specified on EPC. My best guess is that an official MB replacement shock may come with a new one.


Next I took out the new top mount:



And the new stop bumper:



And mounted both on the new shock. The new boot had to be pulled down around the flange on the shock. I made sure the tab on the lower spring mount went through the hole in the shock basket.
 

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2006 SLK280
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Discussion Starter · #4 ·
Reassembling the spring was probably the most difficult part and it is helpful to have an extra set of hands, which is why I didn't take any in process pictures.


The end of the spring needed to stay at the stop on the lower spring mount and straight around the shock shaft while reattaching the spring compressor. Then I compressed the spring so that the top coil was below the threads on the shock shaft. I attached the new top mount and tightened the nut with the open socket and Allen wrench. WIS recommended 50 Nm for the nut.


Then I decompressed the spring, making sure the top end of the spring wrapped around the mount and the tension was released. I removed the compressor and the new shock was ready to go in the car:
 

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2004 SLK350
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124 Posts
I have the same tool but when i try and reinstall the spring it always seems to pull the spring to one side with the struct shaft moving towards one side of the spring and stops me being able to attach the top mount. The bottom baskets on these OEM shocks seem to rise at a slight angle therefor throwing the alignment off. Does anyone have any advice if you have done this before?

I did not have to use it to remove the spring as the spring had snapped a large portion off and therefore wasnt under pressure.

Thanks
 

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2006 SLK280
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Discussion Starter · #8 ·
I have the same tool but when i try and reinstall the spring it always seems to pull the spring to one side with the struct shaft moving towards one side of the spring and stops me being able to attach the top mount. The bottom baskets on these OEM shocks seem to rise at a slight angle therefor throwing the alignment off. Does anyone have any advice if you have done this before?

I did not have to use it to remove the spring as the spring had snapped a large portion off and therefore wasnt under pressure.

Thanks
Hard to say without seeing it, but if you have the same compressor, I found it very sensitive to where you attach it to the spring. Grab too few coils and it won't be small enough to get the top mount on. Grab too many and it the compressor itself interferes. The plates on my compressor have a lip on the inside edge that seemed to hold things straight.

Maybe play with how many coils you are compressing and/or post a photo?
 

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2004 SLK350
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124 Posts
Managed to get it sorted in the end with lots of swearing, the spring naturally leans slightly one way and when i compressed it i could not just drop the top mount in squarely, I got it as close as i could and then release the spring pressure. It did not drop in place initially but a couple of minutes later i heard it "ping" into place :)

Got to re-fit this side and then strip out the other side and replace with new shock, spring and top bearing.
 

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**Registered 2009 SLK200
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Safety Warning !!!

you should always clamp a coil spring end to end using a suitable spring compressor tool
if not you have no control if one end slips out you have not compressed using the tool .

and they have a force once let loose .
 

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2004 SLK350
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124 Posts
Safety Warning !!!

you should always clamp a coil spring end to end using a suitable spring compressor tool
if not you have no control if one end slips out you have not compressed using the tool .

and they have a force once let loose .
I was using a proper spring compressor and there is no way that it could slip off, it is just that it was seated "fully" flush with bottom of the top mount but it was being held in place by the mount (I am a Health and Safety consultant and practitioner so never take any undue risks). Thanks for watching out for me though :)
 

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**Registered 2009 SLK200
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I was using a proper spring compressor and there is no way that it could slip off, it is just that it was seated "fully" flush with bottom of the top mount but it was being held in place by the mount (I am a Health and Safety consultant and practitioner so never take any undue risks). Thanks for watching out for me though :)
No probs ive seen them go !
even with all the safetys on especially the sports springs they are one of the most dangerous things to do sadly . 😬😬
 

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2004 SLK350
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The top bearing was bolted down so the spring could not shoot off but when you look at the bottom of the bearing it is not sitting completely within the top ring of the spring (it is pressing against the rubber seat). When i released the pressure on the spring it re-aligned (or straightened) the line from the shock through the spring to the top mount and then it dropped into the top ring fully. I had the spring compressor still fitted as an additional control measure until it fitted correctly.
591983
 

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**Registered 2009 SLK200
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The top bearing was bolted down so the spring could not shoot off but when you look at the bottom of the bearing it is not sitting completely within the top ring of the spring (it is pressing against the rubber seat). When i released the pressure on the spring it re-aligned (or straightened) the line from the shock through the spring to the top mount and then it dropped into the top ring fully. I had the spring compressor still fitted as an additional control measure until it fitted correctly.
View attachment 591983
Ive always manged to clamp the springs only on fitting numerous Merc springs over the many years never the strut itself .
 

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2004 SLK350
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Ive always manged to clamp the springs only on fitting numerous Merc springs over the many years never the strut itself .
I tried that to start with but it didn't seem how close I got to the ends of the springs full compressed i still couldn't get the bearing to fit over the end of the shock and be able to get the thread through the top mount. I read on the internet (cant remember where as I've read that much) that someone used the bottom basket on the shock so tried it and this allowed me to compress enough to fit the mount. Even with doing it this way, it had to be as fully compressed as i could get it to be able to get the top mount on. Not sure if it is because of have sports springs but it is hte only way i could get it to fit.

591984
 

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**Registered 2009 SLK200
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5,865 Posts
I tried that to start with but it didn't seem how close I got to the ends of the springs full compressed i still couldn't get the bearing to fit over the end of the shock and be able to get the thread through the top mount. I read on the internet (cant remember where as I've read that much) that someone used the bottom basket on the shock so tried it and this allowed me to compress enough to fit the mount. Even with doing it this way, it had to be as fully compressed as i could get it to be able to get the top mount on. Not sure if it is because of have sports springs but it is hte only way i could get it to fit.

View attachment 591984
Maybe because i do mine a diff way !
you learn things as you go along tricks of the trade . 😎😎
 

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2005 SLK350
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9 Posts
Thanks for this DIY, it was spot on and very helpful. For those with the Bilsteins that have the 22mm top rod nut. If you are unable to locate an open socket the Autozone rental tool program has a crowfoot style O2 sensor socket that worked like a champ.

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