Stein Norway

I am not a trained car mechanic, but have a machine engineer degree from waaaay back. I like to tinker with cars, so I bought myself a 2003 SL500 (R230.475).
I recently changed all the front left ball joints as part of my “making the car great again”-project, and with that removed the front left ABC strut to get the ball joint connecting to the control arm replaced (pushed out the old and pressed in the new). Before reinstalling the ABC strut, I filled it back up with hydraulic fluid to minimize air in the ABC lines.
I don’t have the SDS, but I have a iCarsoft MB V3.0. So I cannot do the “rodeo”, but I can check all the values for plunger, voltages level height etc.

So after installing the ABC strut again, upon starting up the car again, I cycled the car up/down through all three levels a dozen times or more. I then drove 100 meters and got the ABC malfunction (grey) alert. So I stopped and plugged in the iCarsoft. I guess I just didn’t realize that the left rear ABC strut had just extended to its maximum level and refused to come down. When checking the voltage it just stage constant on that strut (around 3.8V I think it was), The plunger level is constantly at 0 mm, and the ride height for that strut stay around 50 mm (2 inches).
I haven’t had any issues with the rear ABC strut before this.

Also, when I park the car and turn it off, it sinks down in the front really quick and stays high at the rear.

Any ideas? (I would like to fix this myself, so you don’t need to tell me to go to Mercedes with my car. I’ll do that by myself if I don’t find a way to figure this out or you guys help out :-))
Could it be that air in the ABC line has moved to the rear strut and causes this issue? Would it help to flush the ABC system? Is the “rodeo” an absolute necessity (I’ll take it to an Indy with an SDS if there is no easy way around it :-)

Tom Manning

What is the stored code relating to the white ABC malfunction message?
Sinking down in the front (or rear) is inevitably caused by grit or old seals in the valve blocks. Probably working on the system has caused the blocking valves to no longer seal properly.

I would start with replacing the seals in both valve blocks, or at least the front, and fit the newer white filter in the tank if you haven't already.

The system is self-bleeding so I doubt it's an air lock.

Does the ride height switch work now to raise and lower the car properly or are you still stuck with one high strut? That could be the level sensor for that strut.

MikeJ65

Did you remember to reconnect the wire on top of the strut for the plunger sensor? In any case, you will have a fault code, so start there.

Stein Norway

Thank you Tom, I also doubt it is an air lock. I did flush the system like a month ago and changed the ABC filter at the reservoir.
I forgot to write the fault code of course :-) It is: “C1526-008 fault in hydraulic circuit at right rear suspension strut”.
In addition I do also have a “P202F-004” that is relevant as it might tie in to N51/2?
Does that lead increase your belief that the seals at the valve blocks are the culprit?
Stein

Tom Manning

I found this which may help. It sounds like a fault with the control module.

https://www.benzworld.org/threads/ab...6-008.3085573/

Sinking down at the front immediately indicates that the blocking valves are open when they should be closed. Sinking down over time indicates that they're closed, but leaking.

MikeJ65

This error code is for a case where the strut movement does not match what is being commanded. I would suspect that the control valve is not shifting to a 'lower' position and is probably stuck in neutral or a 'raise' position. I'm not sure what your scanner will do, but in DAS or with a good third party tool you should be able to command the strut to lower and also monitor the control valve current to make sure that the controller is sending the signal to the valve and that there is a current draw indicating that the valve and wiring are not open circuit. The control valve is bidirectional current controlled to allow speed and direction of the strut movement to be controlled. Note that you first need to open the blocking valve, so that the flow path is open. The valves themselves are pretty reliable, but do fail. Sometimes you can see failures on the external housing, but not always.

Hary Gahtoe

What's shocking is the R230 ABC system is Ubber complex but is still repaired by good ol fashion scientific ( aka service analysis ) data analysis. Mostly due to the fact you are diagnosing hydraulic, electric and electronic controls and just old age Not widely practiced by typical MB service techs anymore

What is an issue is finding your particular reason. If you've checked & error codes aren't revealing your problem, it is down to pressure losses or an electronic control issue which is very elusive to nail down.
You "could" have a valve block solenoid leak, an Accumulator beginning to fail, a line starting to fail but your issues sound more electronic control issues.
It's super hard to diagnose a fault you can't lay hands on but it always pays to check electrical connections like the control arm, strut tower top and the valve block solenoids. and the ABC Control module

Personally I had my system go ballistic in a similar nature. It worked fine for years and then suddenly it would cycle the entire suspension ( fr to rear rodeo style ) and lock it rock hard. In old posts I've detailed what I tried but nothing helped and there was No DAS error codes. I took it to MB and an Indy shop who couldn't say what the problem actually was and said the only solution was an entire system replace( $16,000 minimum) without any guarantee of reliability
At present I'm removing all the ABC and installing a full Coilover / sway bar conversion.
Good Luck

Hary Gahtoe

FWIW; Our SL had similar characteristics.
I checked the electrical values of all the strut heights in DAS which were off so I re wrote the #'s and set the height per DAS parameters to be correct and no error codes or numbers.
After repeating the corrections to spec and checking codes multiple times to have the system crash I took it to have my work checked only to have a MB tech and an Indy shop say, yup it doesn't work. No idea what's wrong.
It had no leaks. Held pressure. No codes listed. I did replace the Control Module thinking it was just not holding the DAS commands. NO difference at all.
Our car was a complete ABC system malfunction. All four corners were out of control limit.
Since buying the car 10 years ago I've rebuilt front valve blocks, one Accumulator, two A arm travel sensors, multiple flushes and lastly the Control module. When a MB tech told me he had no clue that was my wake up call. The Indy shop was the final straw. Removing the system has been tough but the car will be reliable and trustworthy with coils and sway bars
I can sympathize what your experiencing.
If you can't recalibrate your suspension and have it stick I'd say it's more a Control module glitch but, you did remove the shock Hydraulic line which I didn't. There are bleeder valves on each corner next to the strut. It wouldn't hurt to fire up the car and try to bleed each line. Not saying it is your cure but no harm trying

Tom Manning

This error code is for a case where the strut movement does not match what is being commanded....

I wonder if, in taking the system apart, a bit of grit has found its way into the valve block and is blocking one of the valves. Disassembling the valve blocks is a bit of a hassle but not really too difficult.

Hary Gahtoe

OP states he has dtc code;
P202F-004 code CAN MESSAGE FROM CONTROL UNIT CGW OR EZS IS MISSING OR FAULTY OR NO OR INCORRECT CAN MESSAGE FROM CONTROL UNIT N51/2(ABC)

Forum member had this situation on an SL55
I found the cause of my wake up problems. It was a relay. Relay K, which is a Motronic relay.Replaced it problem solved.

Stein Norway

Update on this post:
So I’ve been working on this car a lot lately.
My issues with the ABC system does however remain. The car produces error code C1526 for the rear right strut and on/off C1526 for front right as well. The strut plunger, the level measurements and the voltages of the “angle sensor”, and acceleration sensors are all providing logical figures - which is good.
The symptoms are:
When you start the car the car, as you start it, sits high since when it was turned off was in a state of red ABC warning and have the locking valves engaged.
As the car starts, the red ABC warning is reset and the locking valves open. The car then drops down on all sides, albeit to different heights and at different speeds. The rear right does drop ever so slightly, but not much.
Cycling through the different ride heights all work, but when dropping down again does so to different heights and at different speeds.
If you, without driving anywhere, turn the car off. It bounces up, and then slowly starts to sag on the left side.

If you drive, the car rides at different heights, especially the rear right which will ride very high. After a very short distance the red ABC light comes on and the locking valves engage, and all struts are riding high, with the right hand side being higher than the left.

I have taken apart and put together again the valve blocks multiple times, and with that I’ve also replaced the hydraulic fluid multiple times. So now the hydraulic fluid is absolutely clear and fully flushed at least!
I have an issue with getting the valves to sit exactly as they should, and I think that my problems possibly could be related to hydraulic fluids leaking past the control valve - as in the moving part of the control valve and the associated seals (o-rings and Teflon rings) aren’t doing their job.
Does that make sense?

When re-assembling the Valve block I have run in to a problem that I haven’t seen described around here. The head of the control valve (the black plastic part) is possible to turn out of alignment with the rest of the valve. So when you are trying to twist the valve into the valve block (45 degrees for locking valves and 90 degrees for the control valve) to seat the properly, I have experienced that I am unable to figure out how much it is turned as I am actually turning the top part and not the locking part of the valve (I know this as the valve has pushed out after connecting it to the hydraulic system again - and upon inspecting the valve i found that the top has been turned 90 degrees but the valve body hasn’t)

So here are the questions I have now:
- Has anyone else experienced what I am experiencing and if so, what did you do and how did it work?
- Is there a way where I can test the functionality of the plunger in the control valve (does anyone know if you can provide spesific volt/amps to the valve to see that the plunger moves properly)?
- Are control valves interchangeable? I would like to switch them so see if the problem persist or moves to another strut according to how I move the control valve…

MikeJ65

If the plastic housing is loose, I would consider the valve defective and find a replacement. The clips hold on the plastic housing, so if it is rotating, the valve could rotate and come out of the block. They are interchangeable so you could swap them for testing, but I would just replace it. If you have not rebuilt the valve blocks, do that as well. DAS has a way to monitor actual current draw on the valve blocks, but it is in DAS Developer and I'm highly doubt it would be available on you icarsoft.

Stein Norway

Thank you Mike. I think you are right. I’ve just bought a set of used valves, so I guess I’m piecing things together and hopefully I’ll get it up and running again :-)
One question though… What do you mean when you say rebuild the valve block. Sounds very interesting if it will improve the functioning and operational “up-time” :-)

Stein

MikeJ65

You can replace the o-rings on the body of the valve. Many issues are caused by fluid bypasses these o-rings. You can also have internal issues that are not serviceable, but always start with the external o-rings. If you have the white teflon backing rings, leave those in place. If you have the black rubber backing rings, they need to be replaced. Make sure that you get a kit that uses Viton o-rings.

Hary Gahtoe

A; You mentioned the Solenoid ( "black plastic parts" ) are leaking and could be misaligned? So many things could be wrong. Obviously the seals are allowing fluids to escape. Possibly due to multiple issues.
There's a bunch of issues going on. Cause of leaking, the Solenoids could be clogged / the servos inside the solenoid could be aged and damaged/ not seating properly on the block due to clocking
As far as what's causing leaking from the Solenoids ? Obviously the seals are compromised but what's important is what's the cause / correlation between leaks and strut action?

"Are control valves interchangeable"? Not all of them. There's 2 different types on each block

Another thing owners don't understand about the ABC system is aging fluid contamination. As an example I flushed my system while doing multiple tests and Rodeos with > 9L and replaced the filter 3x but when I dismantled the system, fluid in the front was clear but chassis/rear lines were Black. Unless you use the rear bleeder fittings to the struts and open the lines you'll never get a decent full system flush. A closed loop flush does nothing for 80% of the system.

Tom Manning

If you have the black rubber backing rings, they need to be replaced
That is very important: the old black rings delaminate over time and shred little bits of plastic which lodge in the side of the O-rings.

Are control valves interchangeable"? Not all of them. There are 2 different types on each block
All four control valves are interchangeable, and all four blocking valves are interchangeable.

Hary Gahtoe

????
Maybe you mean both of each” type” of Solenoid is interchangeable cause neither will work in the opposite type banks of Solenoid locations on the same or either block;
But, yes you could use a shorter/long version in the same block location at the rear valve block but you can’t swap Solenoid banks

Tom Manning

Shorter valve is the blocking valve. They're all interchangeable.
Longer one is the control valve. They are also interchangeable. You can't swap a blocking valve for a control valve though.

elMacko

My friend, when the ABC gets old and wore out, when you repair one issue, shortly thereafter another one comes around.....if you want to enjoy the car instead of spending your golden years fixing the ABC, bite the dust and switch to coil overs!

Hary Gahtoe

You said ( in a very Fair Dinkem way) they're All Interchangable" What is it? " "They're all interchangeable".BUT; "You can't swap a blocking valve for a control valve though".
That's what I said to begin with, so are you saying all eight can be swapped ("They're all interchangeable") ? Orrrr are saying the same thing just in Ozzy speak ?

Tom Manning

Tedious.

We have control valves, and locking valves. Correct nomenclature always helps. OP asks can he swap control valves to diagnose. Yes he can.

Post #18 is all he needs to know.

Stein Norway

Thanks a lot for all the feedback. It helps. I’ve just bought a used valve block with a set of valves. The stein step is now to take apart both front and rear Valve blocks and separate all valves from the blocks. Then I was hoping some of you knew how to measure that the valve operates as it should (is there a voltage/Amp I can put on the valves to see they operate as they should?), before carefully re-assembling everything (making sure as best I can that the valves are inserted as they should be - at the right angles)

MikeJ65

I would just replace the suspect valve and keep your valve block and other three solenoids. You can check coil resistance, but they usually don't fail electrically and if they do, you should be getting codes for that. Replace the o-rings before you waste your time putting it back together.

Blocking valves are just solenoids and are open with 12V, closed by the spring when not powered. The control valves are actually servos and shift from fill to drain based on polarity and current. You can test them on the car based on how fast the car will raise or lower with a given current. There is no simple way to test them on the bench.