G'Day guys, i have no SLS function and hoping you can help. My accumulators seem OK, ride seems fine and not rock hard as indicative of shot accumulators. The system seems to recirculate ie; fluid is returning into the revoir. I opened the bleed nipple at the valve and fluid shot up high into the undercarriage so it's under pressure (and covered me in the process). I disconnected the lever from the valve and moved it manually up and down but no change in ride height. What could this be, knackered SLS valve etc? The hydraulic rams have no rubber boots on them but otherwise appear OK and i reckon they are probably ok as far as i can tell visually and that i can't imagine they are a real "wear" item, especially both packing it in at the same time. Any ideas?

guys?

The shocks or rams will oil out all over the place when they go bad, so you're probably okay there.

Provided there are no clogs in the line, you're probably looking at bad accumulators or the SLS valve itself.


Check out this cool diagram I found:


http://www.frybrid.com/forum/showthread.php?t=6461

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

cheers, cool diagram. If the accumulators go is it fair to expect the ride to be rock hard in the back? The back seems to operate as is it has shocks on it (soft up and down) which should indicate teh accumulators are ok right? I can't imagine how the valve would die, the lever seems to operate freely up and down, perhaps it has stopped moving something on the inside of the valve?

Hi,not rock hard but annoyingly bouncy and on hard bumps you feel it. What is happening is the tires are absorbing most of the bumps.
If the boots have gone,the shocks won't last much longer.
A quick test is to lift the car up and onto stands, let the wheels hang down.
Undo the flex line into a sphere. it will spray oil out .As the oil lands on the ground (or piece of old cardboard) look at it carefully. if is flat and is still ,the spheres are OK. if it is bubbly like oily coke, the spheres are shot. it only takes a second to do this. The bubbles are nitrogen from the blown spheres.
It takes about 30 minutes to swap the spheres. You need a 13mm socket to undo the mounts, a 17 mm open ender to undo the flex line and a 11mm flare nut spanner to undo the pressure line.
Let the pressure go on the valve by undoing the bleed nipple. I stick a meter long piece of plastic line on the bleed nipple and aim it into an old bottle to dispose of it later.
Once the flex line is off ,I poke a piece of welding wire into the sphere (depends if it has a right angle fitting or banjo bolt) . If the wire goes easily into the full depth of the sphere,it has definitely failed as the diaphragm has blown and the nitrogen has escaped into the oil circuit. No nitrogen,no spring. on a good sphere the wire only goes in a short distance. Poke it in carefully! you don't want a sphere blowing oil at you.
The blown spheres also have lots of oil in them ,good ones don't.
New ones are $300 each and the oz wreckers http://www.uniqueautoparts.com.au/ sell used ones for $100 .
Once you have fitted the new ones and made sure all the lines are secure,open the bleed nipple fully.
Change the filter on the reservoir,and if the oil is really dirty ,remove the reservoir and wash it out . Check the soft suction line and if it's a bit dodgy looking,replace it.
You need at least 3 bottles of the oil, all merc dealers have it ( don't pay any more than $15 per bottle, try http://www.imparts.com.au/ if you your local dealers want more ) .Put two bottles into the reservoir and start the engine,let it idle for a minute.
This will blow all the old crap out of the pressure line.
Stop the engine.
Place stands under the axles so the cars weight is on the springs, Old oil should be squirting from the bleed nipple.
To make the next step easier, I put 4 25 liter buckets in the back of the car. I fill these with water. This pushes the springs right down so the shocks are bottomed out.
Put the last bottle of fluid into the reservoir and start the engine.
Watch the hose on the bleed nipple and as soon as the oil runs without bubbles shut the nipple off. The car should now rise to ride height.
Check the spheres for leaks.
I usually degrease the cars underneath and sit them on a piece of paper .if the shocks are leaking ,this will now become apparent as the oil leaves marks on the paper.
Empty the buckets..
If the shock boots are missing ,the dirt from the road wrecks the lower seal and this kills the shocks ($700 each in Oz )
The oil leaking down also destroys the bottom ball joint as it drags dirts into them. You will then a banging noise all the time .
I don't think mercedes still sells the boots but even a bike tube zip tied into place is better than nothing.

If the height valve leaks the car will settle everytime you stop and pump up when the engine is started . Valves last a fair while but if the oil is allowed to remain dirty they wear out fast.

Bewdy Mate! Great detail! I am new to the SLS thing so this will be a great step by step to sorting it out. I am pretty sure the spheres are OK as the ride in the back seems normal but i have nothing really to compare it to, just what i would expect from any other vehicle. I did open the bleed nipple on the valve with the motor running and the fluid was quite foamy but i put that down to the pressure it was coming out at, would that be a fair guess? The boots on the rear rams are gone but no sign of any leaks, i think the car spent a fair amount of time off the road at some stage. I have read that the rams are pretty robust? I have no idea of the internal workings of the valve but could it still be faulty if the lever moves freely?

Foamy oil means the spheres have definitely gone. The foam,as I mentioned is nitrogen gas .
A crook valve will only stop the car going up or dropping quickly when the engine is off. They are very basic with nothing much in there to go wrong. If the plastic ends on the link rod are broken,buy a new rod but again,they won't affect the ride.
Your ride feels soft(ish) because the tires are absorbing the worst of the bumps. When working properly the ride is fantastic in a 300. They make the old comodes and Fallcans seem like horse buggys in comparison.
The spheres last about 10 years of average driving ,more on babied cars and less on those used for towing boats etc.
The shocks are actually hydraulic rams and the springs are just there to support the weight. they don't do much else. The spheres are the actual springs,and the oil in the rams is pushed against the diaphragm in the sphere. The nitrogen is compressed and that is what gives the car it's soft ride.
If you are unsure,it's not a hard job to take off the flex hose at the sphere and poke a wire into the sphere and check how far it goes in.

The obvious problem i have at the moment is that when i move the lever on the valve the car doesn't move at all. If i sit on the back of the car with the hatch open it will smoothly go down on the (absorbers.actuators) but the car will not pump up. I dissconnected the lever on the valve and lifted it both up and down but nothing. I am still confuesed. If the accumulators were bad would the susspension go down when i sat on it or would it be rock hard? If the accumulators were shot would moving the lever on the valve make the car go up and down still?

Check the spheres
As I said it takes about 10 seconds to take a flex hose off and check the diaphram .Once you are convinced that spheres are OK you can then check the valves operation WITH the engine running.
If the car doesn't go down when the valve position is changed,the spheres are full of oil (blown diaphragm) .If it goes down and up WITH the engine running the valve is OK. As I said,the main problem with the valve occurs when they leak internally and the pressure in the spheres pushes the oil back to the reservoir and the car drops.
You don't get a rock hard ride with blown spheres,the tires and the springs offer a bit of resistance which is what you may be feeling ( i don't know how heavy you are ,but i am 140 kg and a SLS car never goes down when i get in the back if all is OK ).
I have offered you all the info I have and I have lost count of the cars I have serviced with self leveling and full hydro suspension.
it's up to you to take this advice and work with it. Cheers!.

Logic says that if all else is good, and the spheres are bad, it will pump up when the leveling valve is diverting fluid to the leveling system. I'd vote for the leveling valve being bad or clogged. When my spheres went bad, still leveled, but rode hard.

Also possible that the pump isn't developing enough pressure for some reason.

__________________

Gone to the dark side

- Jeff

I have never seen a clogged valve. if the oil is that dirty it blocks the valve,then pump,struts and spheres all need replacing. The oil will last indefinitely as long as it is clean. ( I did 600,000kms in my W126 without ever having to change the suspension oil ) If it goes black ,thats a sign the rear seal in the pump has gone and engine oil is being sucked into the system. While that won't harm the struts,the heavier oil will cause the spheres to fail.
ned Kelly says his oil is foamy, Only one thing makes it go foamy and that is the gas from the spheres. As i see it,he is guessing what is wrong rather than simply checking the spheres First.
A worn valve will leak oil externally before any problems with ride height become apparent.
A worn valve Will not affect ride quality,it's a just a spindle with holes in it that open and close ports to allow oil to pass according to the position of the arm.
he says he can see oil coming back through the filter,the valve is obviously not blocked ( blockage is impossible considering we are talking of a pump which will reach pressures exceeding 2000 PSI,yes Two thousand) .
A worn pump will not lift a car,Simple.

The fluid returning to the resevoir isn't foamy at all, would it be foamy at this point if the accumulators were shot and nitrogen was mixing with the fluid?

What you see is normal,after passing through the filter it won't be foamy looking... Reread my previous posts. it's easier to do it my way than guess what is wrong.

No, not if the nitrogen had already escaped. If so however, the ride will be rock-hard in the rear.

Go to the diesel forum, many of us have had SLS failures on the wagons, and resolved them, and we all seem to have the same diagnosis over there.

__________________

Gone to the dark side

- Jeff

Like I said before,I have lost count of the number of these things I have changed and I've been doing it since 1980. The gas remains in the oil because it's in the struts and the spheres and like I also said,Don't guess,just undo either of the hoses from any of the spheres,poke a wire into it and see how far it goes. Besides Where else did the foam come from?
So simple yet I continually here all these weird and wonderful ideas on how to diagnose bad spheres. On later model cars Like Neds W124,the Springs are supporting more of the cars weight than a W123 Wagon and the car will ride OK but you tend to feel more jolts than normal.