1983 300td SLS re-install

[GRpufnstuf]

Hi diesel folk. Wasn't sure where to post a w123 SLS question. it's a diesel so here I am.

I recently acquired a 1983 300td. It belonged to a friend who neglected everything but engine and trans maintenance.

He also pulled the SLS pump and installed the SLS Conversion .com kit.
It's ok but the shocks are old and and the springs are noisy in the seats ( missing rubber?) and aren't stout enough for any real weight in the back without a real saggy rump.



SO -
most of the SLS piping/tubing and valve situation is still in place.
I picked up a bunch of used SLS parts - 2 pumps, 5 struts, 2 valves, 2 pressure reservoirs, and some misc tubing and oils.
I have read about rebuilding the pump and valves.

I think I'm going to re-install the SLS

Wondering what I need to know/watch out for?

Also need to source some stock springs ( though i Might retain the heavier conversion springs?)
Also would like to replace hoses where possible. I don't have the u shaped metal pipe that comes off the pump
and I'm sure there are a few other parts I'll be wanting.

I'd also love to rebuild the struts if possible but can't find info.

I'll keep reading about individual parts rebuild/replacement. Just curious if there is something that I MUST do while putting it back in.

[BWhitmore]

Once back together the system needs to be bled of air in the lines. If I remember correctly there is a bleeder valve located on the SLS height control valve.

[ngarover]

If the stuff is all basically off and you want to do it right, here are some good steps to follow.

1. Replace the rubber bits in the rear. I'm talking the Sub-frame mounts. These can run you 300 bucks but I can almost promise you they need to be replaced.
part # for TD is 123 350 03 75 and part # for a sedan is 123 350 01 75 The wagons version is slightly different and made out of a harder rubber than the sedans.
https://www.pelicanparts.com/More_Info/1233500375.htm?pn=123-350-03-75-MBZ&fbclid=IwAR3BFzQEjHI8IZVnGOBF8Miss-5yV8EUZygXIgPeRF0FyAl1T9p1ZZ_zBqg

The worn out mounts cause the car to sag. The car should sit at the correct height on it's own with just the springs. IF that's not the case, then you have work to do.

2. Might as well rebuilt both the sls leveler at the rear of the car, and the pump at the front. I've done the leveler myself, not the pump yet as mines still working fine with no leaking. You know when they leak cause the fluid will turn black from oil contamination from the engine. There are kit's available from the Merc Source guy. Peach may be able to put something together if you asked them.

3. Replace the spheres. They are cheap, might as well just get it done.

4. IF the struts you have are not leaking, don't worry about them till they are. you can have them resealed at a local hydraulic shop for about 180. That's what I paid here in Chattanooga to have mine done.

5. rebuild that high pressure hose coming off the pump in the front. it's not hard, I did mine in the garage with basic tools, and the ends are totally reusable. there are instructions here on peach.

In my opinion, a working SLS system is a dream. Setup correctly your car will ride fantastic.

[GRpufnstuf]

Originally Posted by BWhitmore

Once back together the system needs to be bled of air in the lines. If I remember correctly there is a bleeder valve located on the SLS height control valve.

thanks for that. I'll hook up my mityvac and pump some fluid through once i've got all the rubber replaced and things rebuilt. AND located that bleeder

[GRpufnstuf]

Originally Posted by ngarover

If the stuff is all basically off and you want to do it right, here are some good steps to follow.

1. Replace the rubber bits in the rear. I'm talking the Sub-frame mounts. These can run you 300 bucks but I can almost promise you they need to be replaced.
part # for TD is 123 350 03 75 and part # for a sedan is 123 350 01 75 The wagons version is slightly different and made out of a harder rubber than the sedans.
https://www.pelicanparts.com/More_Info/1233500375.htm?pn=123-350-03-75-MBZ&fbclid=IwAR3BFzQEjHI8IZVnGOBF8Miss-5yV8EUZygXIgPeRF0FyAl1T9p1ZZ_zBqg

The worn out mounts cause the car to sag. The car should sit at the correct height on it's own with just the springs. IF that's not the case, then you have work to do.

2. Might as well rebuilt both the sls leveler at the rear of the car, and the pump at the front. I've done the leveler myself, not the pump yet as mines still working fine with no leaking. You know when they leak cause the fluid will turn black from oil contamination from the engine. There are kit's available from the Merc Source guy. Peach may be able to put something together if you asked them.

3. Replace the spheres. They are cheap, might as well just get it done.

4. IF the struts you have are not leaking, don't worry about them till they are. you can have them resealed at a local hydraulic shop for about 180. That's what I paid here in Chattanooga to have mine done.

5. rebuild that high pressure hose coming off the pump in the front. it's not hard, I did mine in the garage with basic tools, and the ends are totally reusable. there are instructions here on peach.

In my opinion, a working SLS system is a dream. Setup correctly your car will ride fantastic.

Thanks, I've been wondering about rear suspension bits. I'll start with the subframe. Looks like i can manage it myself once I have the parts in hand.

I'll call peach about the pump o-ring and seal. I wasn't feeling enthused about spending $70+ for an oring, seal, and "spudger" from mercedes source. I do appreciate that maybe they did the research to find the correct size ring and I will buy if it's the only sure option but that still feels steep.

And yes I will rebuild all that I can and replace the rest. I have 1 strut that has new rubber mounts so I'll start with that one and select a clean one from the other 4 with my fingers crossed.

thanks for the advice. I'll get pics as I go and post a little thread about it when done

[BWhitmore]

Tom Hanson, Parts Manager at the Mercedes Classic Center in Irvine, told me years ago that the SLS shocks hardly ever fail or leak. The test for a bad accumulator is to remove the metal tubing and using the eraser end of a pencil insert the eraser end into the accumulator gently. You should feel light resistance. If no resistance, the diaphragm inside the accumulator is torn or ruptured. The SLS height control valve can leak both internally and externally. Kits (consisting of O rings) are available to rebuild the height control valve. The bleeder valve on the height control valve is normally capped with a black rubber cap to prevent dirt from entering.

[Maxbumpo]

Originally Posted by BWhitmore

Once back together the system needs to be bled of air in the lines. If I remember correctly there is a bleeder valve located on the SLS height control valve.

Best method for bleeding that I've found: loosen the hydraulic line connection on each strut and allow air to exit here, which is the highest point in the system at the rear of the car. The rest of the circuit is self bleeding - fluid at pressure runs in a continuous loop between reservoir, pump, and control valve. The mentioned valve looks like a bleeder, but is meant for bleeding off the pressure in the rear half of the system prior to working on it.

[Maxbumpo]

You must use the proper fluid for the system.

The engine must have the proper head to accept the pump, or you'll have to come up with a different solution.

You must properly adjust the control valve linkage, which will be a trial and error approach lacking the special tools called for in the service manual.

[Maxbumpo]

At rest, with "fresh" suspension components on the rear (springs, pads, and other suspension bushings), you should measure about 13 inches from the center of the star in the wheel to the outermost extension of the fender directly above the star. This is one way to adjust the control valve linkage. If you adjust the linkage so that higher than base pressure is holding up the rear suspension, eventually the control valve will fail and leak and you'll have a sagging rear end again.

[GRpufnstuf]

Originally Posted by Maxbumpo

At rest, with "fresh" suspension components on the rear (springs, pads, and other suspension bushings), you should measure about 13 inches from the center of the star in the wheel to the outermost extension of the fender directly above the star. This is one way to adjust the control valve linkage. If you adjust the linkage so that higher than base pressure is holding up the rear suspension, eventually the control valve will fail and leak and you'll have a sagging rear end again.

copy that. I may try to re-install the struts with the current "heavy duty" SLS delete springs in place. I don't know how this will change the handling but I suspect I can set that 13" spacing and the valve may even be working less with car unloaded?

[GRpufnstuf]

Originally Posted by Maxbumpo

You must use the proper fluid for the system.

The engine must have the proper head to accept the pump, or you'll have to come up with a different solution.

You must properly adjust the control valve linkage, which will be a trial and error approach lacking the special tools called for in the service manual.

YES, i will definitely use the Mercedes fluid. I have the correct head as the pump was there and now it ain't.

[GRpufnstuf]

Originally Posted by Maxbumpo

Best method for bleeding that I've found: loosen the hydraulic line connection on each strut and allow air to exit here, which is the highest point in the system at the rear of the car. The rest of the circuit is self bleeding - fluid at pressure runs in a continuous loop between reservoir, pump, and control valve. The mentioned valve looks like a bleeder, but is meant for bleeding off the pressure in the rear half of the system prior to working on it.

sounds logical thanks for the advice

[GRpufnstuf]

Originally Posted by BWhitmore

Tom Hanson, Parts Manager at the Mercedes Classic Center in Irvine, told me years ago that the SLS shocks hardly ever fail or leak. The test for a bad accumulator is to remove the metal tubing and using the eraser end of a pencil insert the eraser end into the accumulator gently. You should feel light resistance. If no resistance, the diaphragm inside the accumulator is torn or ruptured. The SLS height control valve can leak both internally and externally. Kits (consisting of O rings) are available to rebuild the height control valve. The bleeder valve on the height control valve is normally capped with a black rubber cap to prevent dirt from entering.

thanks! That makes me feel a bit better about using unknown struts to start. I have 5 to choose from and they are all fairly free of obvious leakage mess.

[moon161]

PeachPartsWiki: Self Leveling Suspension Valve Rebuild
PeachPartsWiki: Self Leveling Suspension Accumulator Replacement

I got an SLS valve rebuild kit from the MB classic center, included o rings, a little valve body and a bb for a releif valve I think, about $42.

TD subframe mounts are cheapest at the classic center, $240 for a kit with some fasteners, IIRC.

[GRpufnstuf]

Originally Posted by moon161

PeachPartsWiki: Self Leveling Suspension Valve Rebuild
PeachPartsWiki: Self Leveling Suspension Accumulator Replacement

I got an SLS valve rebuild kit from the MB classic center, included o rings, a little valve body and a bb for a releif valve I think, about $42.

TD subframe mounts are cheapest at the classic center, $240 for a kit with some fasteners, IIRC.

Thanks moon161 -
I do see cheap subframe bushing kits on the Interwebs but I imagine they are junk? I know MB OG will be the better quality part overall.