w123 SLS help

[ajschank]

I have done massive amounts of reading as everyone recommends to do on this topic but seem to have exhausted all possible material.


I have an 82' 300TD with roughly 378,000 miles that I purchased with the SLS working, granted it had been sitting for 8+ years before I bought it. Brought it home, got it running and by some miracle the SLS was infact working. Previous owner had replaced the accumulators, and that's all I know for what has been done too it. I did a fluid flush, and put on a new res and all seemed good. Couple weeks of driving and the old lines rusted through and had a leak, luckily blew out in my garage not while driving around. I ran all new feed and return lines because I was going be doing one line so why not another. New lines installed and I was back in SLS business. Then I noticed it was sagging one day and it no longer rose up when sitting on the truck area. So I went down the forum rabbit hole and rebuilt the SLS pump because that seemed most logical for not rising. Still not rising, so I went and rebuilt the SLS leveling valve since its cheap and not sure if it had ever been rebuilt. Threw on a new height adjustment rod while I was back there. Still not rising! Okay, maybe the pump is junk, sourced a used one from a car I knew had working SLS to just give it a try. Still no luck. I know there is pressure to the back as I cracked the line loose on the SLS valve and had plenty of fluid coming out. Also very steady flow from the return line.



I am at a loss, there are no leaks anywhere in the system, the fluid is still semi clear, no evidence of oil in the system, and engine oil level is normal. Where do I need to look to next? Bad accumulators don't seem to allude to leveling issues, more so ride quality, which seems pleasant. Is it a possibility there could be a blockage from accumulators to the struts themselves? Anything anyone could suggest would be appreciated greatly.

[resto108]

Also have an 82 TD. Will the ride height change when you manually move the leveling valve? Disconnect the link from the valve to the sway bar, start the engine and move the valve all the way both ways and see what happens. Be careful though, the car will lower with the engine off, so don't lower the car on yourself.

[ajschank]

Originally Posted by resto108

Also have an 82 TD. Will the ride height change when you manually move the leveling valve? Disconnect the link from the valve to the sway bar, start the engine and move the valve all the way both ways and see what happens. Be careful though, the car will lower with the engine off, so don't lower the car on yourself.

I have tried that with no luck, I would think it would at least attempt to rise/lower even if the pump wasn't as powerful as it used to be.

[shadetreemechan]

Something is not adding up. If you have pressure to the valve and the manual adjustment of the valve does not change ride height then your valve must have an issue. Are you sure you reassembled it correctly?
The main plate in the inside of the valve can be put in backwards and it goes together but doesnt' work. Any chance that happened?

[ajschank]

Originally Posted by shadetreemechan

Something is not adding up. If you have pressure to the valve and the manual adjustment of the valve does not change ride height then your valve must have an issue. Are you sure you reassembled it correctly?
The main plate in the inside of the valve can be put in backwards and it goes together but doesnt' work. Any chance that happened?

See I thought that was the problem so I took it apart again and double checked everything, and all was were it should be(o-rings, springs, ball bearings..) Double checked with the pelican parts posts and I had the instructions left from my kit. I am really just baffled at what could be going on here. Is it possible the valve itself is just junk and letting the pressure pass through and going right to the return? I will check the lines at the struts themselves to see if there is any flow in the mean time as a last ditch effort to figure out what the heck is going on.

Thanks for all the thoughts so far!

[shadetreemechan]

There is nothing to fail in the valve but the orings springs and bearings. If they are right it is. My next thought would be air in the system. Most will self bleed with a little run time, but maybe that is your issue? Is this a car that is sitting in shop and you run and work on it every now and then, or are you driving it? I did have one that didn't want to bleed after valve rebuild and a day of driving got it working again.

[tdhawk]

I just redid my rear end and rebuilt the sls pump and valve because my rear was sagging. When I got to the sls, it was clear that the lever was loose on the valve shaft and the lever was loose on the sway bar. So, the valve itself was not being activated.

new subframe mounts, trailing arm bushings, and differential mount raised the rear of the car to normal if empty.

85 300TD. 399k daily driver

[ajschank]

Originally Posted by shadetreemechan

There is nothing to fail in the valve but the orings springs and bearings. If they are right it is. My next thought would be air in the system. Most will self bleed with a little run time, but maybe that is your issue? Is this a car that is sitting in shop and you run and work on it every now and then, or are you driving it? I did have one that didn't want to bleed after valve rebuild and a day of driving got it working again.

It is not my daily but I do try and get it out every other day or so for a run to the store and whatnot. I did bleed it briefly at the valve and didn't see any air necessarily. I will try to bleed it again.
As for the arm not being tight enough on the valve itself, I did check for that, and I can see it moving the bar fine.

Edit 9:29pm 1/31/20: Went and bled about half a quart out of the bleeder on the sls valve itself, and still no sls. Checked for fluid at the accumulators, and it did have plenty of fluid coming out. Tightened up all of my line ends for sake of air possibly getting into the system somehow. I don't think it can be air in the system from my new lines since it worked great for a week or so once I replaced the lines. Even checked for any kinks and the line and everything is in the same condition as when I installed. Fluid is good in color too. GAHH

[ajschank]

Originally Posted by ajschank

It is not my daily but I do try and get it out every other day or so for a run to the store and whatnot. I did bleed it briefly at the valve and didn't see any air necessarily. I will try to bleed it again.
As for the arm not being tight enough on the valve itself, I did check for that, and I can see it moving the bar fine.

Edit 9:29pm 1/31/20: Went and bled about half a quart out of the bleeder on the sls valve itself, and still no sls. Checked for fluid at the accumulators, and it did have plenty of fluid coming out. Tightened up all of my line ends for sake of air possibly getting into the system somehow. I don't think it can be air in the system from my new lines since it worked great for a week or so once I replaced the lines. Even checked for any kinks and the line and everything is in the same condition as when I installed. Fluid is good in color too. GAHH

UPDATE: So I rebuilt pump #2 I had because why not. Still not working even after doing that. From that point I was thinking SLS valve was not letting fluid to the struts. I decided to test that by taking off the feed lines to the accumulators themselves and see if the valve would increase/decrease fluid based on movement. I let the accumulators drain until they stopped, about a 1/4 out of the left side, right side was dry by the time I rolled myself over there. Then I went to test the valve and after a few ups and downs of the lever the rear started to bounce up and down a little! What a miracle. Must have just been a TON of air in the system as suggested above. Now I am cruising down the road smooth and level!

[shadetreemechan]

Good to hear. Your story had me stumped.