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.



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.



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.


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.



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


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.