Well, the $9 repair of my rear SLS leak is provisionally successful. The story:
I jacked up the back of the car, high as I could get it. Two jacks, two jackstands. I sprayed PB Blaster on all the hydraulic fittings. The height valve may have been messed with, the locknut isn't anywhere near the socket on one end. Looks to me like the shaft seal on the left cylinder is blown. Won't know for sure until I get it out. Need to do some reading, next. I opened up the trunk to dry out, water had gotten in. I did some reading, so I felt qualified to remove the rear seat. (This is harder on a car with the reclining rear seat option, I've done plenty of the others. The manual wasn't very helpful at all.) First remove the two 10mm bolt heads visible along the seat bottom, near where the release clips are on a non-recliner. That lets the seat bottom lift up and out, and you have to unplug the heating elements along the way. (Unplug the backs, too.) The seat back was trickier. Remove the _three_ 10mm bolts that are tucked under the seat back, one of them in the center underneath the plastic shield for the recliner motor, and _not_ the two visible ones that are attached to the geared track. That lets you lift up on the seat back, releasing the upper posts from the holes in the reclining rack. Then the seat back comes out of the car. _Now_ remove the two 10mm bolts holding the reclining back frame to the geared tracks, and flip the frame up enough to allow the sound padding to be pulled back. This exposes the area where the two plastic body plugs have to be removed, but first you might have to unclip the radio amplifier and the seat heater relay to get them out of the way. Once everything is out of the way the two plastic body plugs may be pried out, exposing the hydraulic strut connections. 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. Unfortunately I was out of time to proceed further. 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 buy 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 activesuspensionsystems.com 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 degrees 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, 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. I called Rusty, and the boot is not separately available. 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 and quenched them in water, thus annealing (softening) them, and attached the hydraulic hose. I put a quart of the special hydraulic fluid 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, except that I'd forgotten that we didn't have snow tires and I managed to put us into a ditch! A kindly neighbor pulled us out. Once home again I put the snow tires on, cleaned up the work area, and put the car away. Still no sign of leaks. I need to put the rear seat back next. -- Jim _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
