Badly leaking SLS - PeachParts Mercedes-Benz Forum

NoSparkNeeded · #1 06-18-2018, 05:42 PM

I finally crawled under after just adding fluid for a month

. The leak is on both
sides coming from directly above the rear struts. Looking at a diagram, they
call it "pressure line pressure reservoir spring strut". It appears that there
are small hydraulic pressure bags inside the springs above the struts. I'm
getting too old to do really major lay on the floor jobs. What is involved
replacing those two reservoirs? Any chance of doing the majority of the work from the top? Sadly I may just get rid of the car if it's too much work. The wagon runs very well, interior is great, only 150k but I just cannot do big
jobs any longer.

NoSparkNeeded · #2 06-18-2018, 07:23 PM

Online and here. Wow the cheapest struts were close to 600.00 bucks!
I see now that the leaky reservoir is part of the strut. Can these struts
be changed without a spring compressor. I read Mercedes takes a specific
type. Will a generic compressor work? What would you guys estimate the labor
would cost in case I decide not to tackle this? Thanks

vollpreuss · #3 06-18-2018, 08:58 PM

Hear you about laying on the ground doing repairs. Not something I want to do often at this point in my life.

In answer to your questions - One does not need a spring compressor to do the job. Most of the work is up top. Remove the carpet and remove the bolt holding in the strut. The fiddly part is the hydraulic connector and related lines. Hopefully they are not rusty.

The bottom is 2 large bolts and drop the strut out. I had my wagon on ramps iirc.

I gambled on a used strut and lost. Got to do it again with a new one. Won't do that again.

BirthdayBenz · #4 06-18-2018, 09:36 PM

On my 85 wagon there was a coupler that went between the hard line and the top of the strut. You can see the coupler screwed into the strut above the 10 inch mark on the ruler in the below picture.

Over time, the coupler in my car developed a crack when the upper strut mount bolts came loose. Perhaps you just need a new set of these. I'd removed the carpet and check the upper strut area as vollpreuss mentioned in the earlier post.

Maxbumpo · #5 06-20-2018, 09:24 AM

If you are really motivated, these struts can be taken apart and new seals fitted. Search this site and the intertubes, you may find something.

Maxbumpo · #6 06-20-2018, 09:28 AM

Here's a write-up from a guy who rebuilt a hydraulic strut for the SLS on a 126 car.

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I got the control link removed from the valve. To grip the flats on the ball I needed a thin 8–9mm wrench, which I didn't really have, but I made do with the prybar I'd made for the 380 SL trunk hinge pin operation. It gripped well enough somehow to crack loose the nut. That and a 10mm wrench and I got the link loose from the valve's control arm. I then had room enough to swing the 11mm wrench on the bleed screw. The valve body wanted to twist on its sheet-metal mount, so I used an 18" Crescent-style wrench to put a hold on it. I had the piece of tubing I use for bleeding clutch slave cylinders on the nipple, with the other end in a clean ATF bottle. Rather than the 1/2 liter that should come out, I got maybe half of the tubing filled. Yeah, the system was empty all right!

Anyway, a 17mm offset box wrench cracked loose the hydraulic fitting. I removed the two washers and the banjo fitting and wrapped the open bits with aluminum foil to keep out dirt. I got the two 17mm bolts on the bottom removed, but the 17mm nut on top didn't want to crack loose. I should have tried the penetrant first, because I managed to badly twist the 8mm flat that's on the top of the strut. Oops! I put penetrant on and left it to soak. A little red heat would cure the problem, but applying said heat would be unwise as the gas tank is right next to the nut.

After a couple of hours of soaking I got out a rubber mallet and a stick of wood. I wedged the wood through the keyhole shaped body hole and spun the strut with the wrench until the hydraulic fitting wedged up against the wood. I then put the vise grips on the twisted flat on top the strut and struck the wrench with the mallet. Between the penetrant and the shock transmitted against the vise grips and the stick the nut popped loose. It was then a simple matter to raise the tire a bit with the jack, to release the tension on the strut and then remove it bodily from the car. The strut seemed to be in very good shape, apart from the leaking. MB P/N 126 320 46 13, Sachs P/N 012400 102 178 R.J (According to the EPC, this is used in 1988+ cars.) The ruined accordion boot looks like MB P/N 448 006 10 0?, the last digit (and a half, really) is obscured by a vent hole. This part number doesn't seem to be in the EPC. There's also a 53932 and a 1–2 molded into it, and a mystery logo that looks a bit like a hand giving the 'OK' sign.

I cleaned it off some and pulled back the damaged accordion boot. I could see a circular snap ring inside the strut body, so I got out a bar clamp and used it between the protruding shoulder of the plug and the shoulder at the top of the strut. Modest pressure caused the plug to push in fractionally, releasing the tension on the snap ring. It is clear that this strut isn't much like the one I found the rebuild article on.

A little digging with some small screwdrivers got the snap ring out of the strut, whereupon the end sealing plug could be pulled out. There was a second snap ring inside that kept in the piston, that came out much the same. The piston itself has what looks like an engine compression ring, and it seems there may be some fine holes covered with spring washers in it. (I could see how the damping might be set by this.) No way the piston could be considered fluid-tight. The difficult part was removing the ball-joint end from the piston's rod. I found a couple of flatter than normal wrenches. One of them, an Indian 5/8", I ground flatter and opened up the jaws a bit to fit the thin flat on the piston rod. The 3/4" fit as-is on the ball joint end. A bit of banging on the wrenches on the anvil cracked loose the threads, then I could just unscrew the ball joint. With that off the rubber accordion boot and the sealing plug slid right off the end. The sealing plug has a fat O-ring on the outside, which I don't think was leaking, and a blue plastic seal ring backed up with a rubber O-ring on the inside. The two rings are kept in place by a staked-in cup. I don't know how one would find replacements for these seals. I'm going to try calling hydraulic rebuild houses in town.

The ball joint feels good, and its boot is good too. Only the accordion boot and the rod seal appear to be bad.

Seems to me that the auxiliary spring pressure of the strut is set by the diameter of the rod versus the pressure in the strut, and that the amount of damping is determined by the larger piston diameter (and the size of the valved leak holes in it) as it plunges back and forth through the fluid that fills the cylinder. (A lesser amount of damping is due to the smaller amount of fluid flowing to the accumulator spheres on compression. [Determined by the rod size.] The ratio of the piston to rod size no doubt sets one of the characteristics of the suspension.) The seal plug is responsible for keeping in all the fluid, of course, sealing the piston rod against the pressure inside the strut. It's a rather elegant design.

...I called around town to hydraulic shops, and most didn't want anything to do with it. The gal at American Seal Company, an affiliate of American West Chrome, said to bring it in and they'd have a look at it. They weren't too sanguine initially, but once I picked the seals out of the plug things started looking up. They looked pretty normal to her and she got out the calipers for a bit of measurement and then ran upstairs. When she came back down she said that I should get a lottery ticket today! She plopped a seal on the counter that looked just like what I'd pulled out, except that the plastic was brown. The two parts I bought were this MKR-22X29.5X3 Metric Buffer (Date code 12/21/06, SKU 146886), at $7.36, and a MOR38X4 Metric O-Ring for the outside of the plug, at $0.80. The total bill came to $8.87, a far cry from the pushing $400 that a new strut would run to. It remains to be seen, however, whether I can get it back together in a leak-free state. The big problem is the hard plastic pressure seal, which I believe went in before the pieces of the plug were staked together. Perhaps if I heat the ring in boiling water it'll be soft enough to put in place the same way I took the old one out, but without deforming in any permanent way. She said that if I ruined that one another was more than a week away, as the one I bought was the last one on the shelf.

I also hear that LX 470 Suspension Accumulators | Nitrogen Globes | Land Cruiser Damping Globes might rebuild these struts. Probably not.

Reading indicates that the steep interior slope of the buffer ring should face inwards, and that customarily such seals are used in conjunction with a secondary seal afterwards. (Fluid that gets past the buffer seal is captured by the secondary seal, and pumped back into the cylinder past the shallow slope of the buffer ring on its return stroke.) Well, there is no such seal here. There is also customarily a wiper seal at the outside to keep out grit, but I suppose that an intact accordion boot takes the place of that. The same source indicates that heating the ring in hot (150 °F) water is appropriate to soften it for ease of installation.

Pan of hot water ready, I heated the plug (a bit) and the old seal. The plan was to push the seal into the plug from the narrow piston sleeve end, using a suitably-sized socket to fill the large diameter section of the plug to try to keep the seal from going in past the retaining lip and into the large section of the plug, in an attempt to get the seal to seat in its channel without damage. After practicing a few times with the old seal to get a feel for it I installed the new seal. I think it went fairly well, at least it didn't look damaged or deformed. I then used brake cleaner to sluice everything out and then dribbled ATF onto the sliding surfaces as an assembly lube. I installed the rod into the plug, then the piston into the cylinder, and then the plug into the cylinder. The two snap rings went in easily. The piston slides smoothly, but of course I won't know if it's actually sealed until I reassemble the system and try it out.

I cleaned the accordion boot in a pan of hot TSP, which worked pretty well, and it looks bad enough that I doubt gluing it back together will be worth the effort. More holes than not. I really need a new one.

...As I'd missed my chance to call to try to order an accordion boot today, and because I could find no mention of them in the online parts ordering systems or my copy of the EPC, I began gluing up this one. Shoe Goo, of course. If I can't get another boot this'll be better than nothing.
More gluing, I guess...

It might be possible to find something from a place like Gardan Mfg., but their off-the-shelf selection didn't look that promising. The boot needs an extension range of 1.75"–6.5" (overall length), an outside diameter of no more than 2.25", and a clamping flange of 1.5" on one end, and 7/8" on the other.
I contacted them with these specifications, and they quoted $72 each. Too rich for my blood, I think.

I reassembled the strut. The hard part was, of course, getting the repaired but still fragile rubber boot installed with its retaining spring circlips. Eventually I prevailed. I then installed the strut in the car. That was easy, especially when compared with getting it out! I heated the copper hydraulic sealing washers red-hot with the acetylene torch and quenched them in water, thus annealing (softening) them, and attached the hydraulic hose. I put a quart of the special hydraulic fluid ($12) in the tank and started the engine, and manipulated the leveling valve. When I next looked the tank was empty, so I put in the second quart. The car then started going up and down with the valve. No sign of leaks. I reattached the control link to the valve and took the car for a drive. It worked fine. Still no sign of leaks.

Maxbumpo · #7 06-20-2018, 09:28 AM

Another option is finding a good used strut, which may not be too easy.

ROLLGUY · #8 06-20-2018, 09:54 AM

Yet another option is to ditch the SLS totally and go with just springs and shocks. There are kits available on the www.

NoSparkNeeded · #9 06-21-2018, 11:50 AM

This makes everything clear. I'm just too old for an all day lay on the floor
and reach over my head job. It looks though, like I can do all the hard stuff
standing up

. The fittings look like a source of pain, but the rest should be
tolerable. Just to be sure, I think I'll bite the bullet and buy a set of those
600.00 Sachs. I don't want to take a chance on having anything fail. The
boot on one of mine looks like it has been gone a long time so the shaft
is likely toast. Anyway, now I have the full picture in my head so perhaps
I'll attempt one last gnarly job

sgnimj96 · #10 06-23-2018, 03:01 AM

It's kinda weird that both side were bad at the same time. Also seems like if the hydraulic rams were blown it would be sitting really low and not just leaking.

anyway,
Taking those struts out is a lot of crawling around in the back. There is a allen bolt that holds the top of the strut that strips out pretty easily- I had to put JB weld in the stripped hole with the allen tool in it and let it cure, got it out the next day.

and that's just a normal thing that can go wrong.

If you really don't want any more problems with it, I say go for the conversion to regular shocks. I just saw this... SLSconversion dot com. My SLS system had all kinds of unexpected setbacks, went back into it many times, used about 3 gallons of a 5 gal bucket of fluid over a couple months before it was right. Rebuilt the valve, changed spheres, both rams . Then there's was the actuator mechanism itself that connects to the sway bar. Sway bar links were the only things that seemed easy.