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  #1  
Old 07-23-2011, 10:36 AM
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W123 sls repair . . where to start ???

Hi everyone, I was lucky enough recently to purchase 2 matching 83 300td wagons for a bargain steal of a price. they both drive wonderful, except that the rear end is sagging and doesnt seem to rise when the car is running. these are my first w123 cars and first time with the mercedes self leveling suspension, any suggestions on where I should start at to try to diagnose the problem? thanks !

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  #2  
Old 07-23-2011, 10:44 AM
JimmyL's Avatar
Rogue T Intolerant!!!
 
Join Date: May 2004
Location: Sunnyvale, Texas (DFW)
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Quote:
Originally Posted by mplsbenzo View Post
Hi everyone, I was lucky enough recently to purchase 2 matching 83 300td wagons for a bargain steal of a price. they both drive wonderful, except that the rear end is sagging and doesnt seem to rise when the car is running. these are my first w123 cars and first time with the mercedes self leveling suspension, any suggestions on where I should start at to try to diagnose the problem? thanks !
Yep, with the "search" function. Use "SLS" for your search criteria. Get comfortable and read read read.....
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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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  #3  
Old 07-23-2011, 11:02 AM
Biodiesel300TD's Avatar
|3iodiesel300T|)
 
Join Date: Dec 2004
Location: Albany, OR
Posts: 4,845
Start off reading through this guide on Troubleshooting your SLS -
Self-Leveling-System - How it works, and troubleshooting the system

Make sure the linkage is connected in the rear. If that is connected then the rear not rising with the car on is SLS pump related usually. The reservoir could be empty, or the pump is toast. The pumps on these cars are pretty stout and aren't commonly the problem but it does happen. The next culprit would be a leak in the system. This leak may show up as drips or it may be internal on the SLS valve or the pump. Both can be rebuilt.

Check the fluid in both. Make sure it's full. To do so you need to run the car and fill the bottle until it start coming into the reservoir via the return hose. Make sure to load the rear a few times with a couple hundred pounds while filling the res to make sure all the air is bled out. Then see if the rear comes up. If so then you may just have a leak in the pump that needs to be fix. If nothing changes and or your res is full then the pump maybe toast. Make sure you're getting fluid returning to the res. If not then the pump is not pumping.
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Andrew
'04 Jetta TDI Wagon
'82 300TD ~ Winnie ~ Sold
'77 300D ~ Sold
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  #4  
Old 07-23-2011, 11:12 AM
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Andrew, above, has become our resident SLS expert. Follow his advice!
Research so you know all the components, their names and functions. Then you can use his advice to work through the system.
Ancient Chinese proverb: "It's always the accumulators"........
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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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  #5  
Old 07-23-2011, 03:04 PM
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pump here $50 pls shpn
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  #6  
Old 07-23-2011, 04:51 PM
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Posts: 18,350
Check fluid level. Check that pump is working by observing return line with engine running. Confirm adjusting rod on control valve is in place. Put some hefty wenches in the back and see if it pumps up.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #7  
Old 07-24-2011, 03:46 AM
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Quote:
Originally Posted by JimmyL View Post
Andrew, above, has become our resident SLS expert. Follow his advice!
Research so you know all the components, their names and functions. Then you can use his advice to work through the system.
Ancient Chinese proverb: "It's always the accumulators"........
I second that, lol! My accumulators were shot, no oil in reservoir but evidence of a new pump - refilled bled, replaced accumulators, rebuilt sls valve, fixed rusted arm bracket, replaced high pressure hose -works great, amazing system. Tons of sls info -happy reading!
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  #8  
Old 07-24-2011, 09:15 PM
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Location: Richmond Virginia
Posts: 309
Replacing accumulators and proportioning valve rebuild are in your future. Both jobs pretty easy.
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1996 E300 110,000
1985 300TD 212,000
1980 300D 238,000
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  #10  
Old 07-24-2011, 10:37 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
Join Date: Apr 2009
Location: Winnipeg, Canada
Posts: 422
I just replaces the high pressure hose on mine. I was wondering if the smoothness of suspension is affected by this system or does it simply deal strictly with the leveling of the rear end according to weight, and the actual suspension, (how easily you feel the bumps), is up to the springs.?
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  #11  
Old 07-24-2011, 10:51 PM
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|3iodiesel300T|)
 
Join Date: Dec 2004
Location: Albany, OR
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Quote:
Originally Posted by azitizz View Post
I just replaces the high pressure hose on mine. I was wondering if the smoothness of suspension is affected by this system or does it simply deal strictly with the leveling of the rear end according to weight, and the actual suspension, (how easily you feel the bumps), is up to the springs.?
The SLS and the springs work together on all aspect of rear height and ride quality. Worn SLS parts will affect the ride quality. If it's really bouncy in the rear, it's accumulators. If it's really hard it's accumulators. It's always the accumulators....except when it's not.

If the struts are blown you'll likely see leaks and might also result in a bouncy ride, but they don't blow out too often.
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'04 Jetta TDI Wagon
'82 300TD ~ Winnie ~ Sold
'77 300D ~ Sold
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  #12  
Old 07-24-2011, 10:59 PM
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/me wishes I had an SLS on my 300D.

Full trunk = nose in the air.
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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)
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  #13  
Old 07-25-2011, 06:48 PM
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Orv Orv is offline
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I can vouch for the robustness of the pump. My car had a completely empty reservoir when I got it. No idea how long it had been that way. The previous owner didn't think it had SLS -- he was under the impression the previous owner had taken it out -- so probably the entire time he owned the car.

I wasn't too optimistic about the pump still being good, but when I put fluid in the tank it hoisted itself right up, and has worked fine since.
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  #14  
Old 07-25-2011, 10:51 PM
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Location: Kona, Hi
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I'll second the comments that this system is fairly simple and robust. Early on in my ownership I was pushed to remove the system, although it requires maintenance, I am glad I retained it.

Best of luck.

Be sure to browse the tech section and read the many many threads dedicated to the SLS systems.
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83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.
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  #15  
Old 12-31-2011, 09:48 PM
azitizz's Avatar
MB 1985 300TD Wagon
 
Join Date: Apr 2009
Location: Winnipeg, Canada
Posts: 422
So I just replaced both accumulators. They were both filled with oil, and as I drained them some of the oil came out black. On the right hand side accumulator snotty glumps of black looking oil (perhaps dissolved rubber?) came out.

One thing I was wondering. I noticed on the new accumulators, there was a piece of plastic just inside the threaded hole where the line screws in. Not the plastic cover to protect debris from getting in and/or moisture that comes from the factory and you pop out, but deeper inside, about 1/2" down or so a little white piece of plastic was in there looking like it was completely blocking the passage way into the reservoir.

Is this something that should stay in there it wasn't obvious or doesn't look easy to remove. There is a bit of a slot in it it seems, like to be able to stick a screwdriver in but it doesn't come out easy and the slotted groove isnt deep enough to make it seem like a screwdriver should easily fit in. I never ended up turning it, and installed them both as they were. I haven't started up the car yet (my key isn't working now and axles aren't done yet)... so I was wondering if anyone knows what Im talking about and knows if these are meant to be taken out or to leave them in.

My old ones just had nothing like that in there and if I take a flashlight it seems I can actually peer right into the accumulator and see the bottom. Has anyone opened one of these up before?

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