560 sec sls valve

[GILBY]

okay,

Had the sls valve replaced today.

Basically the old one wasn't raising or lowering the car. Drove home from work and the seemed harsh, I looked underneath at the valve and the leveling arm was pointing downwards about 30 degrees.

I know It's supposed to be parallel with the sway bar thingy how's ya father.

What I wanna know is how's the car still maintaining ride height? It's doing the same thing as the last valve.

Cheers

 

[talbir]

When the Srs valve is replaced, the system does need to be filled with oil, and the valve bled using the bleeding valve at the top of the valve unit. If you can get the car on a lift, start the engine, disconnect the ride height bar that connects valve to anti-roll bar and move upwards to raise the rear of the car. Then lower the arm fully and car should drop back. It's like replacing a brake caliper, the item needs to be bled, filled with oil and operated to be made functional.

Again make sure oil is pumping through the system - check by removing the lid of the reservoir to see if oil is gushin back through the return pipe which comes into the lid of the reservoir.

Unscrew the bleeding valve on the top of the self-levelling valve whilst doing this to ensure no air lock in the valve.

Once confirmed that the valve is raising/lowering car, then if it's still a harsh ride, then the shock absorbing 'accumulators' may need replacement. These are the black spheres found bolted under the car near each rear spring/strut. About £100 each but if never replaced in 100k miles, then they are likely tired.

Another cause of the harshness is usually the rubber grommets/washers at the top of each strut - there are two very fat ones, both at the top of the strut which sits under the retaining bolt but one that goes on the top of the strut and sits on underside of the car frame from where the strut pokes back inside the car to be tightened. That is the crucial rubber piece that needs replacement. A few pounds from MB for the rubber pieces (4 in total) but you do need to remove the rear seats and the struts to change these items, so a couple of hours of work. Only changing the top most rubber (which can be done without removing the struts) will not achieve any change, it's the rubber under the frame that needs to renewed.

Finally the rear is usually raised through getting revs to about 2k on the heavier Mercs such as w126.

talbir

 

[bolide]

I went through a programme of getting the ride back to normal on my last W124 Estate. I changed the spheres and the strut top rubbers, as Talbir suggests, and the ride reverted to its usual wafty standard

The rubbers are so cheap it makes no sense to not change them. A bit like from ARB bushes

Nick Froome

 

[jaymanek]

Note that moving that lever wont translate in a sudden movement, it will take time to move up and back down, especially if there is air in the system.

Changing the spheres is a good job to do, however every one we have done has required new pipes.

 

[GILBY]

Thanks for the responses.


I noticed this morning the front of the car is really high in the front, I get a little over 4 fingers under the arch. The rear 2 fingers and It feels easy to push down on the front of the car when it's running.

If the arm on the lever is pointing slightly downwards is the sls system actually working?

What else apart from the pump and the valve raise or lower the rear?

 

[hotrodder]

Gravity lowers the rear, the pump raises it.

With the engine running the pump pumps fluid round the system. The SLS valve diverts fluid according to the 'instructions' it receives via the mechanical linkage...

In it's 'neutral' position fluid is returned to the resevoir and the (basic) pressure is maintained in the struts
When the suspension has been compressed enough (loads of Americans on board etc) the SLS valve moves closing the return port and increasing the pressure in the struts to 'pump' the back of the car up until it reaches it's neutral position
When the Americans get out the suspension is unloaded which moves the valve again allowing the pressure to bleed off (fluid returned to resevoir) and the back of the car to return to it's static ride height

As said when the system has been worked on it needs to be bled... the bleed nipple on the SLS valve isn't the highest point on the system hence manually 'working' the valve to 'move' air through the lines. They will self bleed but unless you've got 1/ an estate, 2/ a load of Americans to put in the boot and 3/ time to go for a drive it can take a while hence manually cycling the valve before reconnecting the linkage

Is pump actually pumping?
If yes (fluid flowing etc) then could it be that someone has messed with the linkage in the past? The linkage that connects to the valve is adjustable and if someone has used it to try and lower the car it could be placing the SLS valve in the 'empty' position when the car is unloaded. The lever on the SLS valve pointing 'downhill' suggests it's in the emptying position i.e. doesn't matter how new or well everything is working, the SLS system thinks the back of the car is too high and so want's to let it down rather than raise it...

 

[GILBY]

Thanks for the detailed analysis.


I took the car back to the shop this morning and they readjusted the valve. It's not pointing downwards anymore, but it still doesn't look right, it's pointing a tad upwards now. The car isn't raising any higher though, "kraut ******* was definitely playing mind games!"I stood and watched car raise, then I asked to lower it again but it wouldn't. Should it be lowering as fast as it raises? At that point I just had enough with the kraut ******* and left by the way I'm a Brit living in south Florida.

 

[jaymanek]

With my cars, whenever I have adjusted that valve, I have had to go for a drive for it to settle at its new height.