84 300td sls - PeachParts Mercedes-Benz Forum

Walter K · #1 05-31-2015, 10:04 PM

Gents,

I have been working on details on "Martha", the 84 300TD that I picked up in April. I changed the leaking oil cooler line, replaced the motor mounts, pop tested the injectors, replace the broken bushings in the shift assembly, put new cylinders in to hold the hatch up, etc.. One thing that desperately needed attention was the SLS system. On anything less than a very smooth road, the back end hammered over bumps.

The PO had said he couldn't keep fluid in it for more than a couple of days driving, yet the canister has maintained level, and I could not find any leaks anywhere. After reading the FSM, I had come to the conclusion that I had failed accumulators, as hammering is a symptom of that. I put the car on ramps and crawled under to check the leveling valve while I was at it.

What I found was that the leveling valve was on release all the time. The lever attached to the torsion bar was loose, and the weight would release the valve fully all the time. I tried to take the link that couples the lever to the arm of the valve off only to have the plastic bushing crumble in the process. When you break a part, that means it needed replacing anyway, right?

Anyway, I decided to test the valve, and finally figured out that the SLS does not raise the back of the car very quickly, but the system is working. I showed my good wife when she came home from work the valve and how it was working. She was a little startled with how fast the back of the car drops on full release!

The system holds pressure and does not drop the back end over several days (not sure how long it holds, it has not dropped).

I tried to order a replacement linkage 10 days ago, only to find out both places I tried did not have them in stock. I am supposed to see it on the 16th of June.

In the mean time moved the valve until I thought the back of the car looked somewhat level, and measured the distance between the holes on the levers. I took a piece of 1/2 x 1/8 steel, drilled two holes apart the distance I had measured. I turned two headed bushings up 6mm in dia out of UHMW plastic I had on hand with a .19" dia hole in it for a 10-32 socket head cap screw. I put this in place of the factory adjustable linkage, and used lock nuts on the screws. I forgot to take a pic before I installed it.

I tested it by having two people sit in the back, and system raises the back end up. When they stood up, the back slowly went back down. I'm pleased that even though it is a temp fix, the system works.

Martha rides very nicely with the temporary linkage. What a difference! I wanted a car that had not had the SLS taken out as I have some items I will be traveling with that are not light, and wanted the feature of the SLS.

I think I have the back a little high. The FSM refers me to section 40-310, which is not in the manual. I did finally find the section elsewhere to look at, but it said to take values from a chart that were not included in the section! I guess at this point I will just adjust it until it looks level when I get the replacement part in.

Regards,

W.

Maxbumpo · #2 06-02-2015, 01:00 PM

Walter,

Adjusting the control rod for the SLS calls for some special tools, but I think you can do a "close enough" job through trial and error. The only "gotcha" to look out for is mis-adjustment which will make the rear end too high by keeping a pressure above the normal base pressure, which will drastically shorten the life of the control valve, and the replacement price will make your eyes water.

If you thoroughly read the section in the factory service manual which explains the operation of the system, and then attempt to adjust so as to avoid a "too high" condition but still react to a decent sized load in the back, I think you'll be satisfied.

New control rod for the valve: If you've still got the center piece, you may be able to purchase new ends from MB Classic Center in CA. I recently had the same experience of crumbling ball joints, found that new ends were about $15 vs. entire new rod was about $45.

Walter K · #3 06-04-2015, 04:13 PM

Thanks for the info. Somehow I had missed your reply post.

I will check on the linkage ends. I saved the parts. Looking at what little was left of the plastic, I suspect that each end had plastic parts glued together in the assembly process.

At this point, I think I will level the car by measuring the height of the front bumper with a measuring tape, and adjust the rear to match. Or I might put some weight in the back and adjust it then, checking to see afterwards with the weight out where it sits.

Thanks!

W.

Maxbumpo · #4 06-05-2015, 09:15 AM

Walter,

I forgot some very useful numbers!!

These were reported by a couple of 123 wagon owners from years ago, and I found them to be pretty close for my euro wagon. Note that all had relatively "fresh" rear suspension (i.e. new rubber bushings, known-good springs, new rubber caps on the tops of the rear springs). Measuring from the center of the star in the wheel to the center of the belt line trim strip, using a tape measure stretched vertically and taut over the fender arch--18 inches. From the center of the star to the point where the tape contacted the fender arch was 12.75 inches. Measurements were on level concrete, no load in the vehicle. Make sure that you have base pressure in the system at the time of the measurement. If your measurements are within 1/2 inch, you're probably good. If you have significant side-to-side difference, you've got a different problem than SLS, more likely a broken spring or completely failed bushing, but could also be a rusted and slowly bending rear control arm (btdt).