SL/R129: 1999 SL600 ADS-II Suspension: Symptoms and Possible Remedies
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1999 SL600
1999 SL600 ADS-II Suspension: Symptoms and Possible Remedies
I have almost 69k miles on my 1999 SL600, having purchased it at 55k miles four years ago. Nothing in the VMI indicates ADS or other suspension repair, and the VMI covers dealer service up to my purchase, so we can assume all parts are original. I have never seen an ADS warning light or error code, hence the diagnostic challenge. The car goes up and down without issue via the ADS switch, although at the tallest setting it's comically higher in the front, like a speedboat with its bow pointing up (maybe related to #4 below).
Aside from the high-nose profile when raised, here's what I'm dealing with.
SYMPTOM #1: Over my four years, I've noticed increasing impact harshness in the car, to the point where now seemingly any crack or seam in the road sends an unfiltered THWAP through the chassis and steering wheel (steering damper is brand new). The ride frankly wasn't great in the first place, and it's objectively pretty bad now. Sometimes the chassis will be palpably unsettled by an impact, almost scuttling sideways, as opposed to gliding over the road as I assume the engineers intended. Notably, I just replaced the motor and transmission mounts, which did wonders for vibrations and general driveline refinement, but the flinty ride persists. Tires are Pilot Sport summers with four years/14k on them and decent tread.
SYMPTOM #2: There's no discernible difference between ADS regular and Sport modes. In fact, there never has been.
SYMPTOM #3: There's a lot of squat when I accelerate hard, and a lot of dive when I brake. Is ADS-II supposed to mitigate squat and dive? If so, what might be faulty in my system?
SYMPTOM #4: When I park the car and turn it off, the front suspension sits up too high. It looks goofy. I can't tell WHEN the raising happens -- it's properly lowered while driving at speed -- but by the time I put the transmission in Park, the deed is done. To rectify, I can simply start the car back up, and presto, the nose visibly lowers and stops looking silly. But I doubt Mercedes meant to require another ignition cycle in order to park the car non-goofily.
REMEDIES: I am currently shooting in the dark, hence this post. I'm tempted to have all four suspension accumulator spheres replaced, just to see if that at least takes care of Symptom #1. But it would be ideal to get a clear assessment of all these symptoms before I proceed. Thanks in advance for any thoughts on this.
P.S. @mahunt I'm told you frequent this board now; I am hoping to tap into your 200k+-mile wisdom! (I go by "my500benz" on BenzWorld).
Aside from the high-nose profile when raised, here's what I'm dealing with.
SYMPTOM #1: Over my four years, I've noticed increasing impact harshness in the car, to the point where now seemingly any crack or seam in the road sends an unfiltered THWAP through the chassis and steering wheel (steering damper is brand new). The ride frankly wasn't great in the first place, and it's objectively pretty bad now. Sometimes the chassis will be palpably unsettled by an impact, almost scuttling sideways, as opposed to gliding over the road as I assume the engineers intended. Notably, I just replaced the motor and transmission mounts, which did wonders for vibrations and general driveline refinement, but the flinty ride persists. Tires are Pilot Sport summers with four years/14k on them and decent tread.
SYMPTOM #2: There's no discernible difference between ADS regular and Sport modes. In fact, there never has been.
SYMPTOM #3: There's a lot of squat when I accelerate hard, and a lot of dive when I brake. Is ADS-II supposed to mitigate squat and dive? If so, what might be faulty in my system?
SYMPTOM #4: When I park the car and turn it off, the front suspension sits up too high. It looks goofy. I can't tell WHEN the raising happens -- it's properly lowered while driving at speed -- but by the time I put the transmission in Park, the deed is done. To rectify, I can simply start the car back up, and presto, the nose visibly lowers and stops looking silly. But I doubt Mercedes meant to require another ignition cycle in order to park the car non-goofily.
REMEDIES: I am currently shooting in the dark, hence this post. I'm tempted to have all four suspension accumulator spheres replaced, just to see if that at least takes care of Symptom #1. But it would be ideal to get a clear assessment of all these symptoms before I proceed. Thanks in advance for any thoughts on this.
P.S. @mahunt I'm told you frequent this board now; I am hoping to tap into your 200k+-mile wisdom! (I go by "my500benz" on BenzWorld).
Super Member
Joined: Aug 2019
Posts: 701
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From: Lutz, FL
1997 MB SL600
No more BW for me.
Change your spheres. Try to get either all Febi or Cortico spheres, don't mix and match. Use the proper ZHM oil from MB.
Read the ADSII pdf before beginning and work in pairs replacing the rears (for practice) before the fronts (harder). I now use the $2 cookie sheets from Walmart to catch the oil. I do use an old container to catch the oil on initial bleed, but you need a large flat pan to catch the dripping oil which goes everywhere. Check the tops of the front struts for seepage and replace the O-rings as necessary. Inspect all aspects of the ADS plumbing for seepage (flex hoses, power steering pump, struts, shock absorbers, etc.).
Most ADS owners report the Sport/Comfort rocker as not making much of a difference, I will admit it is subtle. I do engage the Sport setting on unbroken pavement for tighter everything and switch to Comfort when the pavement doesn't allow for a smooth ride. Tire choice does make a difference when selecting Sport or Comfort. My new Generals aren't as compliant as the Continentals, but they are wearing much better.
Change your spheres. Try to get either all Febi or Cortico spheres, don't mix and match. Use the proper ZHM oil from MB.
Read the ADSII pdf before beginning and work in pairs replacing the rears (for practice) before the fronts (harder). I now use the $2 cookie sheets from Walmart to catch the oil. I do use an old container to catch the oil on initial bleed, but you need a large flat pan to catch the dripping oil which goes everywhere. Check the tops of the front struts for seepage and replace the O-rings as necessary. Inspect all aspects of the ADS plumbing for seepage (flex hoses, power steering pump, struts, shock absorbers, etc.).
Most ADS owners report the Sport/Comfort rocker as not making much of a difference, I will admit it is subtle. I do engage the Sport setting on unbroken pavement for tighter everything and switch to Comfort when the pavement doesn't allow for a smooth ride. Tire choice does make a difference when selecting Sport or Comfort. My new Generals aren't as compliant as the Continentals, but they are wearing much better.
Super Member
Joined: Aug 2019
Posts: 701
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From: Lutz, FL
1997 MB SL600
You might want to consider changing out all your rear links. Mine were completely gone when I first got the car at 93K miles. Everything looked fine, but the bushings were soft and the rear squatted and squirmed until it wore the inner portions of the rear tires. Replace the rear wheel carrier bushing for the spring link. Consider changing out the front A-arms for new ones with new bushings and ball joints.
Also, make sure your front and rear height sensor links aren't binding. The ADS cars do tend to settle when parking, but it's more pronounced with bad spheres.
After swapping the spheres, it will take a few weeks of driving to completely purge the system of air. Also, try to remove as much old oil from the system as it is compromised by the escaped nitrogen from the old spheres. This is what is probably causing your settling issue. Drain everything.
Also, make sure your front and rear height sensor links aren't binding. The ADS cars do tend to settle when parking, but it's more pronounced with bad spheres.
After swapping the spheres, it will take a few weeks of driving to completely purge the system of air. Also, try to remove as much old oil from the system as it is compromised by the escaped nitrogen from the old spheres. This is what is probably causing your settling issue. Drain everything.
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1999 SL600
Thank you @mahunt for these excellent insights. You are the mayor of R129 SL600-ville, as far as I'm concerned! I turned your recommendations into a checklist that I'm going to go over with my mechanic here in LA tomorrow morning (I don't have access to a suitable garage for doing this work myself, nor do I fully trust that my wrenching abilities would be up to snuff).
My thought is to break the work into independent chunks, starting with the spheres -- that is, we'll do the spheres and anything else on the list that qualifies as "while we're in there," and then we'll move to the next chunk. Rather than do everything at once, I'd like to understand the marginal benefit of each repair, within reason. There's so little reliable information to be found on these cars. Hopefully a bit more can be produced through this exercise. I'll report back. Thanks again.
My thought is to break the work into independent chunks, starting with the spheres -- that is, we'll do the spheres and anything else on the list that qualifies as "while we're in there," and then we'll move to the next chunk. Rather than do everything at once, I'd like to understand the marginal benefit of each repair, within reason. There's so little reliable information to be found on these cars. Hopefully a bit more can be produced through this exercise. I'll report back. Thanks again.
Senior Member
Joined: Oct 2017
Posts: 368
Likes: 73
SL600
Hallo,
1.: Spheres are gone.
2.: There is no, it is OK
3.: ADS is more weak than standard, it is OK. With ABC, the car would be always straight.
4.: There is a custom option in star diagnosis to always raise the car if you drive very slow. Maybe it is enabled. Or:
The coupling rod(s) are worn out.
Regards
Andreas
1.: Spheres are gone.
2.: There is no, it is OK
3.: ADS is more weak than standard, it is OK. With ABC, the car would be always straight.
4.: There is a custom option in star diagnosis to always raise the car if you drive very slow. Maybe it is enabled. Or:
The coupling rod(s) are worn out.
Regards
Andreas
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Joined: Feb 2020
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1999 SL600
Well, so after all that, my mechanic had me drive down an alleyway full of potholes and just holes period, and he said the spheres seem to be 100%. The car moved around as it should without excessive bounciness. He thinks the impact harshness I'm describing must be due to worn-out bushings. He agrees with Mahunt that it's probably worth replacing the front A-arms, and he recommended the rear links as well. But he didn't want to do the spheres; doesn't think that's my problem.
So, the takeaway for me is that while replacing the spheres might be worth a shot for anyone whose SL600's ride is suffering, they may actually be working properly unless there is suddenly a lot of bounce in the ride that hasn't always been there.
In other news, we had our first kid in December, and I have finally come to my senses about trying to keep this two-seater alongside whatever family vehicle I end up getting. Rather than go down the bushings road, I've decided to sell the car now and focus my energies on finding a Land Cruiser or something. Here's the ad, not sure if it's kosher to post here but I figured there may be a few interested parties in these parts:
https://losangeles.craigslist.org/ws...082413448.html
The late-breaking news on the accident (see Carfax section at the end) was unfortunate, but I tried to adjust the price accordingly. Hoping to find a good home for it this week. My thanks again to Mahunt and AndreasHannover for the great feedback. I'll be sure to recommend this forum to the next owner; it's an amazing resource.
So, the takeaway for me is that while replacing the spheres might be worth a shot for anyone whose SL600's ride is suffering, they may actually be working properly unless there is suddenly a lot of bounce in the ride that hasn't always been there.
In other news, we had our first kid in December, and I have finally come to my senses about trying to keep this two-seater alongside whatever family vehicle I end up getting. Rather than go down the bushings road, I've decided to sell the car now and focus my energies on finding a Land Cruiser or something. Here's the ad, not sure if it's kosher to post here but I figured there may be a few interested parties in these parts:
https://losangeles.craigslist.org/ws...082413448.html
The late-breaking news on the accident (see Carfax section at the end) was unfortunate, but I tried to adjust the price accordingly. Hoping to find a good home for it this week. My thanks again to Mahunt and AndreasHannover for the great feedback. I'll be sure to recommend this forum to the next owner; it's an amazing resource.
Super Member
Joined: Aug 2019
Posts: 701
Likes: 207
From: Lutz, FL
1997 MB SL600
Truly these cars are not for younger folks with new families unless you are both smitten with the car and a good mechanic. Thankfully, I'm both smitten and a good mechanic.
I will say my kids have probably enjoyed (on occasion) having a dad like me. Their high school car, 67 Camaro SS/RS 350 coupe. Occasionally I would pick them up at a friend's house when the other kid had their shared Camaro (twin boys) with my 67 Camaro SS/RS 396 convertible. Oh and when they have a swanky shindig to go to now that they are each married with kid, the SL600. Which is to say, the SL600 has an intrinsic value beyond the expense of upkeep. With the top down, it does sort of make you a rock star. It's a fun car.
I guess the point of this is, you might come to miss the SL600.
I will say my kids have probably enjoyed (on occasion) having a dad like me. Their high school car, 67 Camaro SS/RS 350 coupe. Occasionally I would pick them up at a friend's house when the other kid had their shared Camaro (twin boys) with my 67 Camaro SS/RS 396 convertible. Oh and when they have a swanky shindig to go to now that they are each married with kid, the SL600. Which is to say, the SL600 has an intrinsic value beyond the expense of upkeep. With the top down, it does sort of make you a rock star. It's a fun car.
I guess the point of this is, you might come to miss the SL600.
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1999 SL600
@mahunt No doubt I'll miss the 600. Actually, one thing I love about it here in LA is that few people give it a second look. It's just another old Mercedes in a city crawling with them. But the driving experience, yeah, rock-star level. Acceleration, braking, high-speed stability, stereo sound quality -- all timelessly excellent. And the powertrain has been perfectly reliable for me. The whole car, really. I've averaged about $1,500 a year in maintenance/upkeep, and that's doing none of my own work and paying LA indy prices. I salute the R129 engineers and accept that my next car will inevitably be a downgrade in multiple aspects.
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