DIY: Rebuild the self leveling suspension SLS valve on w123 300TD wagon sagging rear - Page 4 - PeachParts Mercedes-Benz Forum

Adriel · #46 12-27-2016, 09:21 PM

Quote:

Originally Posted by dennislarock

I rebuilt the SLS in my '85TD in 2007... still going strong. 2014... I put in new Rear Struts.
Ride height... is and always has been 13.25" from Center Star to Fender Well ...with no load and empty fuel tank or 600 lbs load and full fuel tank. There are Coil Spring Pads of different thicknesses which can lower or raise the ride height by about 1/4" .

Dennis, than you so very much!

12 1/2" and 12" with one gallon of fuel, so no wonder looks saggy. If the most is 3/4", that only gets half way. Then put a tank of fuel in and bet drop at least half an inch, if not a whole inch.

Again, so glad to have it confirmed saggy springs.

Had to put down Grandmother's old cat yesterday, clean the house, then today deal with insurance and taking the cat down to be cremated. Hopefully tomorrow can get at it.

moon161 · #47 12-28-2016, 09:04 AM

Quote:

Originally Posted by Adriel

...
Ride height with no fuel in the tank on driver's side is 24 1/4" to the wheel well lip and 23 3/4" on the passenger side. I have searched and searched and no specifications....

This sounds like a broken spring.

Rocket99 · #48 12-28-2016, 09:23 AM

There is a Mercedes part number for a rebuild kit from dealers for the valve.

If the problem is sagging overnight sometimes just renewing the fluid can correct that if it is really full of debris.

The baseline pressure contribiting to static ride height is due to a metal to metal interface in the valve and debris can allow fluid to slowly "leak" instead of holding steady overhight.

There is a Mercedes guy in Oak Ridge TN to thank for that tidbit.

Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care

He has put together a kit he sells with components needed to rebuild the radial piston pump. I think the O rings are viton in his kit.

spring struts are now available for less than $100 each from dealers who ship parts for 25% off list price.

Adriel · #49 12-28-2016, 01:54 PM

Quote:

Originally Posted by Rocket99

There is a Mercedes part number for a rebuild kit from dealers for the valve.

If the problem is sagging overnight sometimes just renewing the fluid can correct that if it is really full of debris.

The baseline pressure contribiting to static ride height is due to a metal to metal interface in the valve and debris can allow fluid to slowly "leak" instead of holding steady overhight.

There is a Mercedes guy in Oak Ridge TN to thank for that tidbit.

Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care

He has put together a kit he sells with components needed to rebuild the radial piston pump. I think the O rings are viton in his kit.

spring struts are now available for less than $100 each from dealers who ship parts for 25% off list price.

The rear end never changes height, even with about 200 pounds of load, meaning warn springs. Plus with the out of tolerance side to side, springs no longer in specification. Therefore mist be replaced.

Renewed, flushed, the fluid and no change in ride height or response.

Plan was to avoid the pump for now. If rebuilding the control valve does nothing, then do the pump.

I have springs for all four corners, but only doing the rear for now as no compressor.

Rocket99 · #50 12-28-2016, 04:19 PM

adjust the ride height valve maybe

those pumps stop putting out pressure needed to do the job after the Orings are old, loose resillience, the high pressure fluid blows right by the Oring into the low pressure feed area so there is no output pressure

if so, rebuild kit from performance dynamics

its easy

you'll need a bamboo chop stick or a plastic one to help get it apart

Adriel · #51 12-28-2016, 04:48 PM

Quote:

Originally Posted by Rocket99

adjust the ride height valve maybe

those pumps stop putting out pressure needed to do the job after the Orings are old, loose resillience, the high pressure fluid blows right by the Oring into the low pressure feed area so there is no output pressure

if so, rebuild kit from performance dynamics

its easy

you'll need a bamboo chop stick or a plastic one to help get it apart

Hey, thank you so very much for the help!

Not according to the F.S.M..

With the hose off, how much of a stream should be coming out?

I was getting about what you would use to do a gentle water on the garden.

Now that just got a little bread back from the student loan, yes, don't have to be such a stickler.

Rocket99 · #52 12-28-2016, 04:51 PM

a little trickle to lift the car

don't think so

try to block off the flow

see how that goes

it take pressure to lift the car

a trickle is ok it must be pressure

you are talking to experience here

sounds like you are reading the fsm wonky

operate spring struts with teeny pressure

no

ride ht is both springs and baseline fluid pressure together

you may need springs

Adriel · #53 12-28-2016, 06:26 PM

Quote:

Originally Posted by Rocket99

a little trickle to lift the car

don't think so

try to block off the flow

see how that goes

it take pressure to lift the car

a trickle is ok it must be pressure

you are talking to experience here

sounds like you are reading the fsm wonky

operate spring struts with teeny pressure

no

ride ht is both springs and baseline fluid pressure together

you may need springs

Okay fine, thank you for pointing that out and convincing me.

Here: https://www.startekinfo.com/StarTek/outside/12253/disc%202/program/Chassis/40-310.pdf
In summery, can only be a difference of 0.6" side to side.

Dmitry at Pelican Parts · #54 01-26-2017, 02:07 PM

This is an excellent DIY write up - thank you to those who have contributed!

I've included 2 links that I think and hope will be helpful to any of you addressing the self leveling suspension system in the W123. If you have any further questions, feel free to post a Comment just below one of the articles and someone will get back to you with more detailed info. Best of luck!

Understanding Self-Leveling Suspension

Self-Leveling Valve Rebuild

-Dmitry

Maxbumpo · #55 01-27-2017, 11:03 AM

This is a great write-up, which corrects some of the misinformation in this thread.

Quote:

Originally Posted by Dmitry at Pelican Parts

Understanding Self-Leveling Suspension

My biggest problem with the thread is the incorrect statement that the rear springs alone hold the proper ride height. This is NOT correct! The FSM has a section on the SLS that explains the operation, and proper ride height (in "ready to drive" state) is maintained by both the springs and the base pressure in the SLS. \

The SLS control valve maintains the base pressure at a minimum, if it is in good operating condition. When the car sags after the engine is shut off, the base pressure is leaking off, which can be either from the SLS struts (there would be a puddle of hydraulic fluid under the rear of the car) or from the SLS control valve. Usually it is the valve.

A quick check to see if the control valve is leaking off the base pressure: With the engine off, check the SLS return line at the reservoir in the engine compartment. If there is a steady drip-drip-drip from the return line, the control valve is leaking internally and the rear of the car will eventually sag.

Adriel · #56 01-27-2017, 11:59 AM

Quote:

Originally Posted by Maxbumpo

This is a great write-up, which corrects some of the misinformation in this thread.

My biggest problem with the thread is the incorrect statement that the rear springs alone hold the proper ride height. This is NOT correct! The FSM has a section on the SLS that explains the operation, and proper ride height (in "ready to drive" state) is maintained by both the springs and the base pressure in the SLS. \

The SLS control valve maintains the base pressure at a minimum, if it is in good operating condition. When the car sags after the engine is shut off, the base pressure is leaking off, which can be either from the SLS struts (there would be a puddle of hydraulic fluid under the rear of the car) or from the SLS control valve. Usually it is the valve.

A quick check to see if the control valve is leaking off the base pressure: With the engine off, check the SLS return line at the reservoir in the engine compartment. If there is a steady drip-drip-drip from the return line, the control valve is leaking internally and the rear of the car will eventually sag.

And if sagging all the time?

Seems not getting a rise, loaded her up with two dogs and two bins of heavy suspension parts to test; guess at about 350 pounds.

Whiskeydan · #57 01-28-2017, 05:56 PM

Quote:

Originally Posted by Adriel

And if sagging all the time?

Seems not getting a rise, loaded her up with two dogs and two bins of heavy suspension parts to test; guess at about 350 pounds.

Either your pump is weak or the SLS valve is shot. I have a pump if needed.

It's a pretty simple, reliable system once you get everything right. Typically the first to fail is the nitrogen spheres, valve then the pump. The struts are pretty tough other than the wear on the lower joint.

With the engine running you should see a very steady stream from the return line on top of the reservoir.

Adriel · #58 01-28-2017, 08:37 PM

Quote:

Originally Posted by Whiskeydan

Either your pump is weak or the SLS valve is shot. I have a pump if needed.

It's a pretty simple, reliable system once you get everything right. Typically the first to fail is the nitrogen spheres, valve then the pump. The struts are pretty tough other than the wear on the lower joint.

With the engine running you should see a very steady stream from the return line on top of the reservoir.

Thank you so very much for the reply!

Okay, when did the fluid flush, had really good flow. Seems then my diagnosis of the valve is correct.

B.T.W., no external fluid leaks and did check the sphere diaphragms and intact.