rebuilt sls valve.. feel some resistance - PeachParts Mercedes-Benz Forum

ambush276 · #1 08-21-2016, 06:54 PM

Hello all,

so i have rebuilt my sls valve, installed it back in the car and fired it up. Overnight no more sag! (awesome). I did adjust the ride height and i noticed the level has some tension when going up or down. When neutral it stays neutral, when down it goes down, and when up it goes up... but the level does not have a "fluid motion." It seems to work but i am not sure if that is how it is supposed to operate. (a decent amount of tension when moving the lever).

79Mercy · #2 08-21-2016, 10:34 PM

Its normal to have tension in the valve lever, your just fighting against the high pressure hydraulic fluid in the system.

bsmuwk · #3 08-21-2016, 10:39 PM

it should have some tension running up and down on the adjustment, if it felt loose, your reseal is leaking by.

mine have always been somewhat tight, which is good. as long as you've properly lubed your seals and all, and it's not leaking externally - you're peachy.

*i'm on my 16th rebuild, fwiw.

ambush276 · #4 08-21-2016, 11:46 PM

the ride height seems to always want to ride a little too high. Once i get into the cars it seems to want to raise up some and rides a little high. Should i extend leveling joint even though it won't be even with the pin.

bsmuwk · #5 08-21-2016, 11:55 PM

Quote:

Originally Posted by ambush276

the ride height seems to always want to ride a little too high. Once i get into the cars it seems to want to raise up some and rides a little high. Should i extend leveling joint even though it won't be even with the pin.

you can, gotta remember though, those front springs may be tired and you're thinking it's riding to high when it may not be. have had a few folks come around and be in total disbelief with how high these cars are really supposed to ride. new suspensions work wonders i suppose.

To even it out some, yeah, play with the rod until it satisfies you - it won't hurt anything.

Maxbumpo · #6 08-22-2016, 10:57 AM

Quote:

Originally Posted by bsmuwk

To even it out some, yeah, play with the rod until it satisfies you - it won't hurt anything.

I disagree, sounds like a great way to undue all the rebuild work and cause the SLS control valve to fail again. Setting the rear too high will cause more than base system pressure to be holding up the rear, which in turn will put a higher pressure on the base pressure valve than it was designed for, which may cause it to fail earlier than it should.

Adjusting the rear height is fraught with complications (see FSM for a list of special tools required).

Unfortunately if you've already adjusted it, unless you carefully measured / marked before you started, now you've got to do your best to make it work. One way to set it would be trial and error, with the car in "ready to drive" state as described in the service manual, and with a hydraulic pressure gauge to trial-and-error the adjustment until the base pressure is within spec (and I'm assuming that spec is in the FSM, going to take a look now to see).

Maxbumpo · #7 08-22-2016, 11:14 AM

For a 123 wagon, FSM procedure 32-530 says "adjustment of discharge valve to guarantee basic pressure: 30 + 8 bar". I interpret that to mean that with a proper gauge and the proper procedure, that discharge valve (which operates in the neutral lever position) should open to discharge excessive pressure at 38 bar, and close up after relieving excessive pressure at 30 bar. An adjusted ride height that won't risk damage to the discharge valve should be 30 bar or less, anything close to 38 bar is risking damage in my opinion.

In my case, I did not have a hydraulic pressure gauge or any of the other special tools (for my 124 wagon), so I loaded up the car with the weight specified in the service manual for "ready to drive" which was full load of fuel and all other liquids topped up, spare tire and factory tool kit present and in place, and two adults in the front seat. I estimated a weight for two average adults in 1987 (probably a lower figure than the average adult today, I think I used something like 150 lbs per adult) and used whatever I had around to fill up the two front seats with 150lbs each. I then inserted the pin to hold the lever in the neutral position, and adjusted the control rod to fit, and then test drove the car. My ride height was too low for my taste using this method, so I adjusted it just slightly higher so that front-to-rear of the car showed to be level, and left it at that. Now the rear end does sag under load more than it should, so I've probably got it set on the low side, but I'd rather endure a ride that is a little less than optimal in order to preserve that SLS control valve, which may not be rebuild-able on the 124 cars.