Any way to "test" SLS struts? - Page 2 - PeachParts Mercedes-Benz Forum

ps2cho · #1 03-10-2011, 01:49 PM

Quote:

Originally Posted by 124126140

Is the sway bar rod to the valve lever good? To test sls put 200lbs in the rear and rev at 2000 rpm for 30 secs it should lift.

Yes the leveling bar is good.

I'm not sure if I ever actually tested it at 2k rpm. I think I just loaded it at idle and nothing happened. Will it not raise at idle regardless of weight loaded?

balge · #2 03-10-2011, 02:12 PM

Pretty sure the drill is it needs revving to start pumping up the rams, the pump will be at its minimum pressure at tickover, it makes sense to me it would work better at driving speeds

There isn't that much fluid system in the system normally, maybe if the spheres are ruptured and full of oil it could slow it down even more?

Plus I reckon it needs more than 120kg to actually get the rear end down enough for the sls to kick in....unless I weigh a lot less than I think!

Have you tried taking off the adjuster and moving the lever directly at the sls valve to test that works ? - bear in mind previous cautions lol

cheers!

compu_85 · #3 03-10-2011, 02:03 PM

No you have to load the system down for it to raise. Get a couple buddies to sit on the trunk lip.

-J

ps2cho · #4 03-26-2011, 09:34 PM

Figured out the knocking in the rear....

I was a dummy and accidentally put the passenger side camber arm upside down...Dee dee dee...

You can see the sway bar was working a nice groove in the arm!

124126140 · #5 03-26-2011, 09:45 PM

It's always good to admit your mistakes. I have the same wagon as yours only 78k. SLS is very deceptive, but it does it's job when it works.
Paul

ps2cho · #6 03-26-2011, 11:15 PM

Its the only way to learn!

ps2cho · #7 04-01-2011, 11:07 AM

Tested SLS system....Held idle at 2k rpm with 230lbs loaded in the rear. Used a tape measure, and there was no change in height.
Fluid level is good, and has been for a number of years, so no leaks.

So its definitely not working....what's the next item to check?

balge · #8 04-01-2011, 02:30 PM

Ok, just to make sure we're all singing from the same hymnsheet, I was told to
- measure the height
- load up the wagon till it drops at least a couple of inches
- start the motor and fast idle
- measure the height again - should go back to original height fairly sharp

Next step is get underneath - nice high ramps! and check the lever connecting the valve block to the swaybar. Make sure its actually moving the lever on the valve body. Disconnect from the swaybar to operate the valve to test it

I think you pull the lever down to make the car rise? Worth checking which way...!

If it doesn't move with the lever it could be the pump or valve-body, and that's starting to get beyond my experience....so far, touch wood!

Also worth checking oil is circulating, I think it only shows in the tank when its actually moving the suspension?

babymog · #9 04-01-2011, 06:09 PM

First let me explain the hydraulic leveling function as the fluid sees it. I apologize if this is beneath your level of understanding, but it's a basic place to start.

Since your system is full, and not leaking, we will eliminate all parts except the pump and valve.

The pump pumps fluid whenever the engine is running. The pump is capable of hundreds of PSI so if the pump is working, and has fluid, it must go one of three places.

Is fluid leaking?

Y > you have a leak, fix it.

N> > Is fluid returning to the tank?

Y> This means that either the leveling valve is not calling for lifting (adjustment), or it is leaking internally.

N> > either the rear is raising, or the pump is not working properly (fluid full?).

I suppose it is possible that the pump low-pressure line from the tank could be swollen shut and not allowing fluid to pass so the pump sucks air, but I haven't seen it yet.

If the pump is working, the fluid has to go somewhere. It goes to the valve. The valve is a simple diverter valve with three basic positions:

- If the valve lever is at the level position, it is returning all of the pumped fluid to the reservoir through the return valve and flow to the dampers/reservoirs is blocked.

- If the valve lever is at the above-level position, the valve is returning all of the pumped fluid to the reservoir, and venting the fluid from the hydraulic rams (shocks, dampers).

- If the valve lever is at the below-level position, the return to the reservoir is blocked, and the fluid from the pump is being directed into the dampers.

Since your car is not leveling, and IIRC I believe that you have posted that there is fluid returning to the reservoir (a steady stream I hope), this should eliminate all but the valve. This points to the possibility that the valve is not adjusted properly, or it is leaking internally. I believe that it has O-rings inside, which could be degraded due to the wrong fluid, contamination, or I don't know. I have been told that they are not repairable, which is of course bad.

124126140 · #10 04-01-2011, 06:34 PM

Well said Babymog, I would like to add The system is not instantaneous, my 88 te takes a few minutes of driving to adjust ride height. Disconnect the link from valve to sway bar and move lever by hand to check valve and adjust link if valve works.

babymog · #11 04-01-2011, 06:46 PM

Thanks.

I'd like to add also, that the spheres / accumulators have absolutely no effect on leveling. Your car can level with ruptured spheres, just as well as with good spheres. With ruptured spheres you will have ride/damping problems, completely different symptoms.

davidmash · #12 04-02-2011, 10:19 PM

Babymog's post is spot on as far as I can tell.

I just rebuilt the pump on my car and when the engine is running you can look into the pump reservoir and see a stream of oil coming out of the return line (top of my reservoir) when the engine is running. If you do not see oil returning to the tank then your pump may be bad or a clogged line some where in the system.

If you are trying to get your SLS sorted, you might want to replace the seals on your pump while you are at it. Not a hard job and given the age of these cars I suspect your seals are as hard as rocks (mine were like hard plastic after 24 years.

If you want to buy a seal kit with instructions, call this guy and order a kit

George Murphy

ps2cho · #13 02-16-2012, 01:22 AM

bumping thread as I want to take a look at this once the car is running again.

So it seems like my non-functional SLS is either pump or valve...but a reminder, car ride is perfect in the rear, even with weight so I think the sphere's are functioning fine.

So if I peer into the reservoir I should be able to see if the pump is circulating fluid right?
If it is circulating fluid, it should be safe to say that its probably the valve?

I have not checked what setting the valve lever is on, but as babymog said, 3 settings...but to clarify, do any of those 3 settings DISABLE the SLS? Where "should" it be set at?

If its the valve, can they be taken apart and rebuilt or is it a replacement only? Looks like they are ~$380.

ps2cho · #14 02-21-2012, 04:40 PM

Checked this out today.

SLS fluid is circulating around system -- does that mean pump could still be suspect? Fluid looks "ok" -- not black at all, but its probably time for the change regardless.
Also, with car on stands, valve leveler is at the bottom position.

So to confirm my understanding before I go messing with stuff (I want to understand so I know whats not safe to do), with the engine idling, I should be able to disconnect that nut, and manually move the leveler...If I move it up, the SLS struts SHOULD move, right? Nothing is going to "drop" on me with the car on all 4 jack points correct?

compu_85 · #15 02-21-2012, 05:10 PM

I thought the SLS fluid was light green not medium red