ASR and ADS on a 1996 SL600

[television]

We need info on ASR main ECU,s and ADS with a small bouncing at the front.

I know that moakesr will give some info on the ADS

I will look up what I have on ASR

[moakesr]

LOL, did someone mention ADS? ;)

Anyone care to detail the exact problem?

I have a new acquisition to help :D A complete factory R129 ADS manual, it's in German, but the diagrams and google translation mean I might have a clue what's going on.

[television]

The front end bounces too much at speed, I had told KLP of your problems and said that you were good for help.

Though are are loads of threads all over the world on ADS, I have only ever seen 1 where a solution was found and thats your car

[BlackC55]

I drove it. Its rock hard at the front.

I have had a quick look up on WIS last night and the info seems a little vauge.

I suspect the spheres are at fault. They are not expensive. I think I am fitting them soon.....

I hope nothing goes wrong! LOL

[television]

I drove it. Its rock hard at the front.

I have had a quick look up on WIS last night and the info seems a little vauge.

I suspect the spheres are at fault. They are not expensive. I think I am fitting them soon.....

I hope nothing goes wrong! LOL

Did you drive it at speed, 70-80 mph this is what Nat told me, but he can post himself now

[moakesr]

Crikey, I never thought of myself as unique in fixing it!

Well, if it were my car, I would start as follows:

1. Is the MIL light lit? Does it illuminate when the instrument pack resets during startup?

2. When stationary, is there any movement in the front suspension, i.e. the shock absorber bounce test? If not then it's possible the accumulators have failed.

3. Is fluid being returned to the reservoir when the engine is running? If not then the system may need bleeding.

That's enough for starters :)

[moakesr]

I drove it. Its rock hard at the front.

I have had a quick look up on WIS last night and the info seems a little vauge.

I suspect the spheres are at fault. They are not expensive. I think I am fitting them soon.....

I hope nothing goes wrong! LOL

Sounds like the accumulators, but check for return fluid to the reservoir when the engine is running?

Eurocarparts will sell the accumulators, but the website lists the wrong items, what you need is 620220760 (SPRING LOADER ACCUMULATOR) at a cost of £82.69 each +VAT for OEM Lemforder or Febi items.

GSF do the genuine ZH-M fluid way cheaper than MB, part number is M98001

Good Luck

[BlackC55]

I will do. Its good to know that you have extensive knlowlege in this area. We hardly saw any cars with ADS at dealers, and when you did the foreman would normally repair them. Knowlege is scarce on these systems.

I have done the MB course on suspension. It did not include ADS though. Typical of MB courses.

[moakesr]

I will do. Its good to know that you have extensive knlowlege in this area. We hardly saw any cars with ADS at dealers, and when you did the foreman would normally repair them. Knowlege is scarce on these systems.

I have done the MB course on suspension. It did not include ADS though. Typical of MB courses.

If you need the manual, let me know, I will photocopy/scan it and send it to you, provided no-one reports me for copyright infringement :crazy:

[BlackC55]

I need it please.

See my website for my address.

If you need anything from me just ask.

[television]

On the ASR bit, this is not a fault that happens on this car as man made

Jay has some links and here is one on the faults, and I will add to this

http://pages.prodigy.net/jforgione/MB_asr.html

[KLP 92]

Hi,

Thanks for all the replies.

The exact problem on the V12 SL is low speed bouncy ride. If you hit a put hole the car bounces 2-3 times, mainly at the top of the shock absorbers.

I noticed it first when i was in a petrol pump, a small dip in the forecourt resulted my nhead hitting the pano roof :crazy:

On the way to the GTG the V12 was following and in my rear view mirror i could see the front of the car continously bouncing very finely up and down on a flatish surface, considerably more when hitting pot holes.

The car has a genuine 40k on the clock, but sits for long durations without being moved. The suspension doesn't drop down after being parked up for a while, maybe 1-2 cm at works but comes up as soon as you start it.

I've been looking inot the front suspension set up, theres the valve block, spheres and shocks. Its not an electric issue as that should bring up a fault code and cause the warning light to illuminate.

Any help will be welcome as i need the issue resolved asap. Will be taking the car to Olly's once we get a better idea of the possible fault.

[KLP 92]

1. Is the MIL light lit? Does it illuminate when the instrument pack resets during startup?

2. When stationary, is there any movement in the front suspension, i.e. the shock absorber bounce test? If not then it's possible the accumulators have failed.

3. Is fluid being returned to the reservoir when the engine is running? If not then the system may need bleeding.



1. no
2. Very minimal, when you press down hard and let go the car boounces up and down 2-3 times
3. yes

[Will]

It sounds like very similar symptoms to when the SLS spheres fail on other MBs - not identical but a similar system.

Basically, from what I understand, the spheres fail internally letting the nitrogen out and they have no damping function remaining.

The hydraulic fluid can not be compressed, so the strut becomes rock solid and causes the car to bounce (as it can't damp as it should)

Hope that makes some sort of sense, and it does seem quite likely that this is the case.

Has the hydraulic fluid level dropped at all?

Will

[BlackC55]

I agree and these are my exact thoughts at the moment.

[KLP 92]

Has the hydraulic fluid level dropped at all?

Will

Nope, it was just about the min mark, topped it up 2 weeks ago. It hadn't been topped up for 3 years prior though.

It hasn't come down after 300 miles so its not losing fluid.

Thanks for the info.

[moakesr]

1. no
2. Very minimal, when you press down hard and let go the car boounces up and down 2-3 times
3. yes

It's difficult when I am not there to compare the bounce against mine, but I am 95% sure the front accumulators have gone.

The failure of these will not cause a fluid leak, however it will cause the reservoir to drop, which it sounds like yours has a little. The resulting column of uncompressible fluid will reduce the suspension travel to almost nothing. I found that when replacing the accumulators there is no need to bleed the system, this side of the main hydraulic block is self bleeding.

When I first got my car it had exactly the problem you describe, but was combined with no hydraulic pressure from the pump as this had not been bled properly during an overhaul of the tandem pump. The car was very 'darty' and was 'porpoising' at speed on the motorway. Never having driven an ADS equipped vehicle or an SL before, I wasn't sure what to expect, so initially wasn't aware something was wrong. Interestingly, there was residual pressure in the rear, and the accumulators were intact, so I still had suspension at the rear of the vehicle.

The valve blocks don't seem to fail, and contain two valves of differing flow rates, these are used individually or combined to stiffen or soften the suspension as required by the ECU. Even when the system is locked out or powered down, there is still sufficient fluid flow for suspension travel when pushing down on the wing.

One final note, there are two VERY sensitive accelerometers fitted to the car, one is on the offside front hub, and one is on the nearside inner wing under the bonnet. Under no circumstances shock or hammer any of the surrounding metal, they will fail if you do, and cost around £330 each to replace, thats one mistake I won't be repeating in a hurry :( If you need to use any force around the area of the front offside hub, such as replacing brake pads or disks, then I recommend you carefully remove the accelerometer and refit it when you have finished the job. (In case anyone was wondering why normal wheel movement and potholes don't destroy the accelerometer, it's all to do with frequency and amplitude of the vibration that the sensor is exposed to, the unit on the hub measures low frequency vertical vibrations, whereas a hammer hitting the caliper or disk, which is also connected to the hub, will introduce very high amplitude high frequency vibrations in the wrong axis. The new sensors are solid state and probably much more tolerant, but the old ones are moving mass and strain gauge types that are in a bath of oil, wonderful piece of engineering, but ultimately fragile. Having cost me so much for a new one, the least I could do was take the old one apart and have a look at how it worked!)

I will be scanning the manual tonight, and will send a pdf to Olly tonight with any luck.

[BTB 500]

If you need to use any force around the area of the front offside hub, such as replacing brake pads or disks, then I recommend you carefully remove the accelerometer and refit it when you have finished the job.

Thanks for the warning as my ADS-equipped R129 is having new disks and pads shortly! :)

[KLP 92]

Thanks for the warning as my ADS-equipped R129 is having new disks and pads shortly! :)


Its invaluable information. I do know of a chap that started having warning lights on his dash after changing his discs, it was on an ADS equiped car.

The problem is not many people are aware of this, even in main dealers.

[stats007]

SS Motors in Weybridge have done 2 complete ADS refits that I know of on R129s. Speak to Joe if you get stuck - 01932 821555.

[Dieselman]

Without looking deeper this system sounds very similar to Citroen hydraulic systems.
With the car at normal ride height there should be significant movement available when performing the bounce test otherwise the spheres are shot.

If this car has it's original spheres they will be worn out or punctured and will need replacing anyway before any further diagnosis.

I suspect that will fix it though.

There should be a bleed screw on the side of the main valve block but in reality if the ride height has been up and down a few times the air will be expunged anyway.

BTW. The pattering is a classic symptom of shot spheres as the suspension then comes from the tyres and is undamped.
This fits with the 'headbanging' as well.

[stats007]

Licensed from Citroen if memory serves me correctly.

[Dieselman]

Licensed from Citroen if memory serves me correctly.

Everyone uses Citroen systems, even Rolls-Royce.

They really are the best, but unbelievebly simple as well. Basic hydraulics and in some cases a bit of electronic control for height adjustment.

[stats007]

Just a shame that's the only good bit on a Citroen!

[moakesr]

Without looking deeper this system sounds very similar to Citroen hydraulic systems.

It is similar, but in many ways it's very different.

The damping value is varied at each wheel 10 times a second, according to parameters such as, steering wheel angle, braking effort, chassis acceleration, front axle acceleration, throttle input and I believe a yaw sensor. Sorry if this isn't an exhaustive list, but I don't have the manual in front me at the moment. This produces an anti-dive, anti-squat, and anti-roll effect which is nothing short of remarkable, the smoothness of a Citroen, but also with selectable sporting characteristics and none of the body roll you get with early Citroen systems. Above a certain speed the ride height is lowered by 15mm, it returns to normal height as you slow down. Additionally the height can be raised by means of a switch, once again it will resume normal height above a certain speed.

The nitrogen filled spheres are the weak point of any such system, I regard them as a service item that needs replacing just like shock absorbers in conventional suspension.

I used to drive a Citroen BX and CX, so remember fondly the comfortable ride but somewhat alarming body roll of those systems. I believe they were significantly improved in the later hydractive setup for Xantia and XM?

[stats007]

It's a fairly simple system and not totally active like the Skyhook system on my Maserati as it just swaps between different damping settings.

A brief overview of ADSII:

http://i26.photobucket.com/albums/c133/stats007/ADS1.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS2.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS3.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS4.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS5.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS6.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS7.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS8.jpg
http://i26.photobucket.com/albums/c133/stats007/ADS9.jpg

[moakesr]

It's a fairly simple system and not totally active like the Skyhook system on my Maserati as it just swaps between different damping settings.

ADS II looks more sophisticated than what I have experienced, my car is 1991 so has ADS I

All good fun though :D

[stats007]

Yours is very early, there were a few revisions to ADSI in 1993 I think. Hope you're writing all of this down, Bill ;):D .

[BTB 500]

Well, I've got the thread in my favourites!

Nav and Olly were bouncing my car to compare it with the SL600 :)

[Dieselman]

It is similar, but in many ways it's very different.

The damping value is varied at each wheel 10 times a second, according to parameters such as, steering wheel angle, braking effort, chassis acceleration, front axle acceleration, throttle input and I believe a yaw sensor.
I used to drive a Citroen BX and CX, so remember fondly the comfortable ride but somewhat alarming body roll of those systems. I believe they were significantly improved in the later hydractive setup for Xantia and XM?

No difference at all.

What you describe is a Citroen Hydractive system as fitted to Citroen XM to provide variable damping and spring rates. This was then improved upon and became Hydractive2 then installed on XM and Xantia VSX models and then Hydractive3 which is what was fitted to C5 and C6 cars.
The main difference being the electrical ride height selection instead of mechanical employed upto Hydractive3.

This is the only suspension system that can offer variable spring rates as well as damping rates.

Citroen also have the Activa system which is further advance for handling packages. It gives a supple ride but doesn't allow any body roll past 0.5 degree.

The only difference with this system is the remote mounting of the spheres and standard ride height being set by springs instead of the rams.

[Dieselman]

Well, I've got the thread in my favourites!

Nav and Olly were bouncing my car to compare it with the SL600 :)

When bouncing the rear have somene sit on the boot opening panel as ballast otherwise you won't be loading the suspension properly.

Edit.
Also you can feel when the spheres become hard just by bouncing when you have some experience. They should feel like they've got loads of give gradually stiffening not feeling like the stiffen up quite quickly.
You can also tell by the ride quality as sharp bumps pass through more readily.

[Dieselman]

It's a fairly simple system and not totally active like the Skyhook system on my Maserati as it just swaps between different damping settings.



What does the Masser use Stats? Is that a full suspension by hydraulics setup like a Citroen?

[stats007]

No, Maserati use a Skyhook system which is based on a Mannesmann-Sachs design. Infinitely variable rate coil over dampers - not semi-supporting like ADS.

[Dieselman]

No, Maserati use a Skyhook system which is based on a Mannesmann-Sachs design. Infinitely variable rate coil over dampers - not semi-supporting like ADS.

But no spring rate adjustments, only dampers.

I'm not saying it isn't good or doesn't work, I'm sure it does, but Citroen are the only manufacturer to offer both variable spring and damper rates.

Hydractive systems switch in 1/20th second.

[stats007]

ADS isn't designed for sports cars - it's too intrusive and heavy for one thing.

Variable spring rate can come from progressive springs but even then very few cars use them. Magnetorheological systems on Audis and Ferraris are still just variable damping.

Citroen may be the only car manufacturer, but Bose (http://www.bose.com/controller?event=VIEW_STATIC_PAGE_EVENT&url=/learning/project_sound/suspension_challenge.jsp) offer the same thing.

[Dieselman]

I've seen the Bose system before and it appears a good idea, though I wonder how much energy it consumes being that it requires active electrical input at all times.

Interesting..

The regenerative power amplifiers allow power to flow into the linear electromagnetic motor and also allow power to be returned from the motor. For example, when the Bose suspension encounters a pothole, power is used to extend the motor and isolate the vehicle's occupants from the disturbance. On the far side of the pothole, the motor operates as a generator and returns power back through the amplifier. In so doing, the Bose suspension requires less than a third of the power of a typical vehicle's air conditioner system.

regenerative suspension as well as brakes now then..

[stats007]

It's regenerative, so very little by all accounts.

[moakesr]

But no spring rate adjustments, only dampers.

I'm not saying it isn't good or doesn't work, I'm sure it does, but Citroen are the only manufacturer to offer both variable spring and damper rates.

Hydractive systems switch in 1/20th second.

Just been reading wikipedia about Hydractive, the variable spring rate thing is confusing me, I understand the variable damping, but can't see how it offers variable spring rate? Does it switch additional accumulators into circuit to provide variable spring rate?

Cheers :)

[Dieselman]

Yes, that's the whole Hydractive thing. The different versions then just have different control thresholds and either mechanical or electric height control.

Soft ride = 3 spheres at the front and 3 at the rear.
Sport ride = 2 spheres at each end.

A hydractive car uses a total of eight spheres including main accumulator and anti sink valve accumulator.

Hydractive3 automatically lowers the car at speed for stability and raises it if rough roads are encountered.


Each sphere has it's own hydraulic dampers built in so the less spheres the stiffer the damping becomes as well as the spring rate.

Activa uses additional rams connected to stiffer anti-roll bars. In comfort mode they are all floppy, in sport they are locked up so the anti-roll bar does some work.
If the car rolls more than 0.5 degrees the rams push the car back to being flat again.
All this is automatic with no input required from the driver, but sport mode can be selected if desired on Hydractive1 and the thresholds can be altered to be more sporty on Hydractive2 onwards.

Linky.
http://www.citroencarclub.org.uk/PostNuke/index.php?module=ContentExpress&file=index&func=display&ceid=40&meid=92

[moakesr]

Thats pretty clever!

I always enjoyed my CX, marvelous battle wagon :)

mind you, I thought accelerometers on a 1991 car were exotic, I just love gadgets :)

[stats007]

They are - hence their pricetag!

[moakesr]

I need it please.

See my website for my address.

If you need anything from me just ask.

PM me your email address, I will send you the scanned pdf :)

[moakesr]

I have uploaded the scans as jpg's to picasa. sorry for any quality loss.

http://picasaweb.google.co.uk/moakesr/ADSManual

If anyone wants the pdf original, then please PM me your email addresses.