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My entire front hydraulic suspension bottomed out the other day while doing errands.
This has happened once in the past when the front level sensor linkage broke away from the front sway bar. Easy to spot and easy to fix. This one was tougher to fix, but I had a pretty good idea what the problem was.
Aside from the front going all the way down, the ADS trouble light on the instrument cluster lit and while it was lit I couldn't use the UP/DOWN rocker left of the light switch. I turned the car off and back on which extinguished the ADS trouble light momentarily and allowed the front to rise enough to drive home cautiously. With the suspension fully down the outside edges of the tires can EASILY catch the fender lip and do considerable damage. The lowered suspension can also cause the top of the tire to contact the arch of the fender and the ensuing friction will burn the paint from below. I now have a small quarter of an inch round burn on the driver's side fender.
I ended up replacing the ADS II valve body with a new one I got from a fellow R129 enthusiast (it had an inoperative solenoid valve) that I got in trade for some R129 assistance. I used one of my original valves to replace the nonworking new one and the whole assembly works great.
The problem with my ADS II failure was degraded wiring insulation of the Master Valve Body harness. The harness goes from the 4 valves on the valve body to the 5-way connector near the top of the passenger side strut tower. The insulation looked exactly like the failed wiring on one of the bio-degradable era R129s. The original wiring used colored wiring (brown for ground and other colors for positive) while the new valve body uses wire half as thick and everything is black.
You can easily check your valve body harness condition by locating the 5-way connector on the strut tower face, dislodge it from it's receptical and open the connection. There are a few snap fittings on each side of the connector, just work your way from the wire side to the hinged end. Hopefully, when you open the connector, you won't find insulation bits.
All of the wires on the original harness were fully compromised. I used a multi-meter to check the continuity of the 4 pairs of wires and ALL were compromised with cross bleed. I applied power to each of the individual valve solenoids and miraculously the valves still functioned, but I knew it was hopeless.
You might want to take a peek at your connector or try to view the most forward and inboard valve solenoid's wiring by peeking down from the passenger side air intake horn. You will see the black circular top (with white lettering) of one solenoid just visible inboard of the frame rail but aft of the radiator. Two wires route forward from the solenoid before looping down and back to the harness.
Even reusing one of my old solenoids was troublesome as the black plastic top caps were degraded and split. I re-sheathed the solenoid's 2 wires and soldered them to the new valve body's harness. It was a big surprise and a bit of work, but I saved a bunch by having the new valve body handy. I also replaced the big valve body to tandem pump pressure line than snakes around the oil pan. Both my oil pan stand off fittings had worn off their hose grommets. I've replaced all of the hoses that run around the engine except for the oil cooler and the AC refrigerant lines. The new line fittings seem to be a gray stainless and no longer yellow cadmium.
Can others check their wiring harnesses to see if my problem was a fluke and let me know?
I'll post a picture of the valve body and degraded harness as well as describe the rest of the repair.
The first time my front suspension went down (from the linkage), the fenders were saved by the strut bump stops. When I inspected the struts for damage, I noticed that the only thing remaining of the original bump stops was reddish foam bits. Even the upper strut bellows were damaged by the tires.
In order to insert new bump stops and bellows, the strut would have to be disconnected from the upper strut bearing. This extra step was no problem as I needed to replace the O-rings in the upper strut hydraulic connections (which were seeping). Replacing the O-rings was the hardest part of the strut work. When I removed the upper strut hydraulic fitting in order to swap out the O-rings, I noticed the grommets (2019974481) that seal the fitting as it passes trough the strut tower were in need of replacing.
After checking with the dealership, the grommets are not in stock which is somewhat different from NLA, No Longer Available. They said to keep the request open and I didn't have much hope in seeing a new one and proceeded with the repair (valve body swap and hydraulic supply line replacement). Before I got the opportunity to pressurize the system, MB of Tampa called and said they had 1 of the 2 grommets in. Woo hoo! One grommet was in worse shape than the other, so that one got replaced. The ticket is still open and they will call if another comes in. If the grommet does come in, it means I'll have to depressurize the front hydraulic system to swap it out.
So far I replaced the valve body, both bump stops, both strut bellows, one hydraulic line grommet and the hydraulic fluid supply line from the tandem pump.
The repair of the "new" valve body took a little bit of work, but it's way better than the original. Take a look.
The "green" coloring on the wires is copper corrosion and you can just make out the split fissure on the top of NV21 solenoid.
Oh dear, this looks bad. Thanks for the writeup. I'll take a look at the connector as soon as I can. Seeing as my car is also a 97, I doubt I'll find anything good.
I guess it should be pretty easy to rebuild the wiring harness, but looks like the other end is fixed to the valves? Bummer for someone like me who doesn't have a proper garage... Kind of hard to pull the valve body.
The valve body is a messy item to swap out. I now use large area aluminum single use cookie sheets (Walmart $2.50, sold as a pair) to deal with the widespread dripping. The valve body has 7 or 8 pipe connections AND then the electrical connection that you have to untangle from the passenger side wiring harness. You will snip at least 2 black tie wraps and one reusable clip.
As you can see from the photo the wires run right into the caps of the 4 valves and the valves themselves don't come apart so you have to snip off the old wires, re-insulate the remainders and solder otherwise attach to new wires. You'll notice that there are 2 kinds of valves NV21 and NV22. I think the NV21s are for lowering the front and rear suspensions while the NV22s are for raising the two suspensions. Their orientation on the valve body is critical too, so work with one at a time and take pictures. I used fingernail polish to mark the tops of the valves with dots to correspond with their electrical connector number (2 - 5) AND made a mark between the valve body and solenoid to index the orientation of the solenoid to the valve body.
The one solenoid I took from my old valve body had a filter screen on the bottom that did have a few bits lodged in it. I used heat shrink tubing to re-sheath the wire stubs. My solenoid caps were plastic and brittle with age, be careful with yours.
Sorry to see this happen. It's exactly the problem I had. I still have my old valvebody with solenoids if someone can use them. I'd let it go for cheap. 2 of the solenoids appear to have good wiring still. One solenoid's wiring is completely broken (the reason I replaced it) and the other one has split insulation. The aluminum body is corroded too but with some time I'm sure the solenoids can be removed and saved. Sure beats buying a brand new assembly from MB for $1,000 like I had to!
I checked the connector today. It seems that mine is of the same model as your replacement - the insulation is all black and not crumbling, at least not yet. What's the manufacture date of your car? Mine is from early March 1997. Besides the Carfax report there are no service records before 2018 so I can't be sure, but I doubt the valve body has ever been replaced.
Mahunt, I would like to know more about the flow controlling valves for the dampening rate.
Do you have now a spare block to dissect?
My assumption is that they stop functioning with a certain age, while the coil shows still the right resistance...
In my car for example,I cannot tell any difference no matter which dampening mode I choose....
Are you interested to dig into this ?
Cheers Frank
I would also be curious to hear any findings about this issue. The sport/comfort button does nothing on mine either. There are no problems with ride quality though.
The front aluminum valve body just raises and lowers the suspension via separate hydraulic tracts; one for the front suspension and the other for the rear. The real name of the valve body is: level control valve.
What you guys are talking about are the damper valves that are paired with each sphere/strut combo at each corner of the car.
Read section A7 Funktion ADS II of the R129-ads-ii pdf for an explanation of various components and what they are supposed to do. There's a wonderful diagram on A7 page 2.
Section B8 Damper Valve will provide a full description of the damper valve and it's inner workings. PERHAPS there are internal filter screens that when clogged prevent proper function, but I have no plans on taking apart any of the 4 damper valves in the foreseeable future.
I very much would like to get your old valve body as I am restoring my '94 sl and all the wiring is bedly cracked and crumpled. How much and how can I pay you and get the doner part.
Keith 832 651 7576
Our 2 SL600s are different from each other with respect to the master level control valve (and a bunch of other things). If you take a peek at your level control valve you will see it's quite different from the one I have (see above).
12-01-2019, 01:05 PM
