PeachParts Mercedes-Benz Forum - w123 Self-Leveling-System O-ring replacement DIY

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w123 Self-Leveling-System O-ring replacement DIY

w123 Suspension Valve Removal and Reseal Instructions
Here's a printer-friendly PDF version: Seal Instructions

Here are the location of each of the 5 o-rings inside of a w123 Suspension valve, and how to replace each one. You will probably want a dental pick or some other similar tool to remove the old o-rings without damaging the sealing surfaces.

NOTE: Hydraulic connections are very tight and usually corroded, so take the necessary precautions and use the right tools so you don’t strip any thing.

With the car jacked up and properly supported, remove the hydraulic lines shown in the photo below. You’ll need a 11mm wrench. Be ready with a catch pan, you may loose a few quarts of fluid. Make sure on the supply and return lines you use a 17mm wrench to hold the big connections on the valve, you don’t want to remove those, only the hydraulic lines that thread into them. Once the hydraulic lines are disconnected remove the 10mm nut holding the lever arm to the rod.

http://people.oregonstate.edu/~lindgrea/DIY/SLS/1.jpg

With the hydraulic lines and lever arm disconnected, remove the two nuts and bolts shown in the photo below. Don’t take the other two out yet. They hold the two halves of the valve together.

http://people.oregonstate.edu/~lindgrea/DIY/SLS/2.jpg

Once the valve is removed from the car clean all the grime and buildup off the valve so you don’t get any of it the valve when you take it apart. Make sure the holes where the hydraulic lines go are kept clean, and plugged so nothing get into them either.

O-ring # 1:
Now remove the two bolts holding the two halves of the valve together. Then carefully pull the valve apart. Pay close attention to the way things come apart, it will make re-assembly easier. In my experience the cam sticks to the side of the valve with the o-ring, so that's probably where yours will end up. With the two halves apart remove the old o-ring and clean up the sealing surface. Make sure any solvents are cleaned off, and then put in the new o-ring.

O-ring #1 seals the two halves of the valve together.
http://people.oregonstate.edu/~lindgrea/DIY/SLS/3.jpg

O-rings #2 and #3:
Remove the cam from the valve and set it aside on a clean rag. Then gently pull the piston out of the valve. It can be stuck in pretty tight depending on the condition of the o-ring inside so be careful that you don’t loose any parts. There are two steel balls inside the valve, a small one and a big one, don't loose them.

http://people.oregonstate.edu/~lindgrea/DIY/SLS/4.jpg

Separate and clean each part of the piston assembly. The photo below shows the order they go together, and where o-rings #2 and #3 are located. Carefully remove the o-rings, make sure not to scratch anything. Clean the sealing surfaces and put in the new o-rings. It may also be helpful to give the whole piston a light coating of suspension fluid to help prevent any binding when putting it back into the valve. The small steel ball goes inside the inner piston then is followed by the small spring. The large steel ball floats back and forth in the channel at the bottom of the hole where the piston assembly goes, and should be located toward the center of the valve.

O-ring #2 seals the inner piston to the outer piston
O-ring #3 seals the outer piston to the body of the valve
http://people.oregonstate.edu/~lindgrea/DIY/SLS/5.jpg

Here is a schematic of the valve that might help you assemble the piston assembly. 3d is the small steel ball, which is inside the piston assembly. 3f is the large steel ball, which is in the channel at the bottom of the hole for the piston assembly.
http://people.oregonstate.edu/~lindgrea/DIY/SLS/6.jpg

O-rings #4 and #5:
To get to o-rings #4 and #5 you will have to remove the rod that goes through the body of the valve. Before you remove the lever arm from the rod index the end of the rod and the lever arm so you can put them back together in the same orientation they originally were. Then loosen the nut and remove the lever arm from the rod. With the lever arm off you can pull the rod out from the inside of the valve.
NOTE: Some of the early 123 leveling valves only have one o-ring instead of two. If this is the case on yours just replace the one and save the other.

O-rings #4 and #5 seal the lever arm to the body of the valve
http://people.oregonstate.edu/~lindgrea/DIY/SLS/7.jpg

Reassembly and installation:

Installing the Cam and Lever Arm:
Proper placement of the cam and alignment with the lever arm is key for the valve to work right and sit level when unloaded. After replacing O-rings #4 & #5 put the rod for the cam and lever arm back into the valve. Put the cam onto the rod so it is lined up as in the diagram below. You'll also have to pay attention to which way the rod is rotated. You need to have the notch on the rod for the bolt on the lever arm in the right location. Once you have the cam on and the notch in the right place you can put the lever arm on, and use a 4mm diameter locking rod to assure that the lever arm is in the correct place. Now you're ready to put the halves of the valve back together.

http://people.oregonstate.edu/%7Elin...m_LeverArm.jpg

Re-installing The Valve:
Once the valve is back together re-install it back into the car. Be careful when you thread the hydraulic lines from the accumulators back into the valve. The valve is aluminum and if you cross-thread your connections you will be looking for a new valve. Thread them in by hand and make sure they aren’t cross-threaded before you tighten them with a wrench. You will need to refill the suspension fluid reservoir. The system is self-bleeding so you won’t need to do any bleeding. Start the car and look for leaks. If there are no leaks shut the car down and have a large helper or two child size helpers sit in the back. Then start the car and watch to see if the rear end lifts up like it should.

I have reseal kits available. Contact me if you are interested. I am asking $10 for the first o-ring set and $5 for each additional set. This includes all the o-rings in the valve, a 4mm locking rod, and shipping.

There is a printer friendly PDF version of this DIY linked at the top of this thread.

________________________________________________________________________________________

Good job and Great post Andrew!

Thanks!

.

Oh man, your post is very timely. I've been looking at purchasing a SLS valve rebuild kit from a well-known DIY parts supplier but was choking on the $90 price tag. It includes the piston, spring, ball and a couple of washers. No instructions.

In your experience, how necessary are these particular parts in a rebuild?

First class DYI instructions !!! This needs to be put in the DYI section for others future reference !! Its a pity the Mercedes repair instructions are not of this quality !!!

Quote:

Originally Posted by Carpenterman (Post 2405083)

The overpriced dealer rebuild kit is overkill. The most common problem with these valves is they start leaking, either internally or leaking out of the valve. The parts in the valve rarely break or go bad. They really don't take a whole lot of stress. The valves really just need to be resealed. I've sold well over 100 of these kits over the past couple years and no one has come back and said it didn't fix the saggy rear end. If you need a kit let me know.

I am a satisfied customer of Andrew's. I have rebuilt 3 valves with only one issue, and that was my mistake putting the cam in backwards. :o
I purchased 2 more kits just to have.
I recommend this completely!!

Quote:

Originally Posted by Biodiesel300TD (Post 2404872)

w123 SLS Valve O-ring Kit Info-
I am asking $10 for one kit and $5 for each additional kit. This includes all the o-rings needed to seal the valve and shipping. PM or email me if you are interested.

Here is what is in the O-Ring Kit
http://people.oregonstate.edu/%7Elin...O-ring_set.JPG

As you may know, Citroens have a similar thing to an SLS that they developed in 1955 and is still used, with mods. I would like to know what kind of fluid is used in these systems. The early Cits used an LHS fluid for which brake fluid was a substitute in the US. Laster cars used a mineral based oil that was 100% different and incompatible.
Why am I asking?

The seals for each type of Citroen SLS are different material: either EPDM for the older brake fluid ones,

or

Buta-N for the mineral based ones.

I would assume that the SLS O-rings are the later type, since SLS fluid is probably not compatible with brake fluid, right?

The reason I ask: I must have a million seals and O-rings of both types from 30 years working on Cits. So I'm interested in looking at the rebuild kits with an eye toward making them, last longer.

Has anyone used Viton O-rinds for the SLS??

The kits I have are Buna-N. The fluid you want to use is the picture below.
But mineral oil is an okay replacement for the SLS fluid.

http://www.peachparts.com/shopforum/...6&d=1266268267

Well, I'm investigating my dragging-butt syndrome, and I'm thinking the Valve is the problem.

The fluid in there currently, is really quite hideous, a nasty greenish brown stuff with almost a whitish hue as if there was moisture present in it and Very very 'thin' like water thin, so thats my first job, Change that crap.

--I was thinking of using the same Product that Citroen recommend to use every three years to flush their suspension/brake systems called-'Hydraurincage' for their Mineral LHM based systems, Anyone any thoughts......?

There is fluid re-circulating back to the reservoir when the engine is running, and of a fair quantity of flow, so I'm hoping the pump is OK, as I havent a spare,--At least it appears to be working, but who knows if its developing Pressure!...

Guessing its the Valve thats the main problem, as there are no apparent leaks or fluid losses, Moving the lever on the valve either way has no effect at all, when engine is running or stopped....

Biodiesel300TD-

If possible, Can you ship seal-kits over to the UK?

May I know if these O-ring are Viton or NBR?

Thanks.

NPK

Quote:

Originally Posted by Biodiesel300TD (Post 2404872)

w123 SLS Valve O-ring Kit Info-
I am asking $10 for one kit and $5 for each additional kit. This includes all the o-rings needed to seal the valve, shipping, and the newly added locking rod for adjusting the SLS to the proper ride height. PM or email me if you are interested.

Starting April 16th and going through the end of June I am on the road for work more often than I am home. I won't have internet access, so I may not respond to emails and PMs immediately. I'm not ignoring you, and will get back to you as soon as I can. I will remove this message when I am back on the home front for good.

Here is what is in the O-Ring Kit
http://people.oregonstate.edu/%7Elin...LS/SLS_Kit.jpg

Quote:

Originally Posted by npk (Post 2464872)

May I know if these O-ring are Viton or NBR?

Thanks.

NPK

http://www.peachparts.com/shopforum/2406561-post11.html

Quote:

Originally Posted by Biodiesel300TD (Post 2406561)

The kits I have are Buna-N. The fluid you want to use is the picture below.
But mineral oil is an okay replacement for the SLS fluid.

http://www.peachparts.com/shopforum/...6&d=1266268267

from what I understand, type 46 hydrolic fluid is a compatible substitute, and is fine for testing and flushing the system. it worked in my 79TD for over a year, (and may still be working... I no longer have the car) and it's what I am using in my sagging but 83TD until I can get the pump rebuilt (PM soon to be sent!)
do you know if the 87TD uses the same fluid and has the same Valve kit for rebuild? not that my 87TD has ANY issues, but I plan on keeping it for a LONG time, so "be prepared"