R230 ABC problem

[Calle1]

Hello,

A few days ago I got a problem with the ABC suspension on my 2002 SL500.
When driving on the highway it started jerking sideways like a boat on the sea.
I immediately suspected the ABC although there was no warning light on the dash!
So I stopped and checked the ABC fluid reservoir and indeed there was some fluid missing (dipstick on low).
I drove home carefully (about 15 miles) and when I got home I noticed that even more fluid was missing.
Nothing was showing on the dipstick however I could see some fluid at the bottom of the reservoir so at least it did not run dry.

Today I got some fluid and actually I only had to add about 6 ounces to fill the system.
Now the car rises when pressing the height button one and two times - but not as much as earlier.
I also noticed the front RIGHT wheelhouse being a bit lower than the rest of the corners. (about half an inch)

Later I hooked the car up to STAR diagnosis and all the values looks good and the ABC pressure sensor says 190 bar at idle which I guess is good so (hopefully) the pump is not broken?
I also did the rodeo test and the pressure dropped to about 140 bars when doing the test and after completed it rose to 190 again.
During the test a white ABC error message appeared on the dash "Visit workshop" and the fault code from STAR is the following:
C1531 001 - Left front suspension strut moves although locking valve is closed

After doing all the STAR tests and lowering/raising the car several time with the car on idle I can't see any notable amount of fluid missing so I guess it's a small leak somewhere but would it be big enough to cause the issues?
No signs of fluid under the car.


Any thoughts?
Should I also bleed the system and change the filter?

It's also worth mentioning that the white ABC message has appeared a few times before after having the car on idle for a longer time.

 

[LostKiwi]

It really needs to go on diags to read off the codes.

 

[alexanderfoti]

If the car body is moving randomly vs external influences there is a problem with either a lateral or horizontal acceleration sensor.

They can be tested in star but if they are intermittent it won't show up.

The ABC is doing what it usually does, compensating for body movements. It detects these body movements using these sensors.

If the sensors report the car is leaning when it isn't, it will do odd things trying to counteract a movement that is not there.

Suprise suprise they are usually affected by damp etc. Occasionaly it's a wiring fault or ecu fault.

 

[Flyinspanner]

Re the tiny fluid loss.
Just check the valve blocks, if you see any unions are wet, then try to just carefully tighten them.

Keep an eye on fluid level, - how is the colour of the fluid? Should be nice and clean. Has it ever been changed?

you can get a fluid level drop if one of the pulsation spheres has failed, (internal diaphragm breaks) - that could have been the cause of a sudden momentary pressure drop, which may have started the jerky body movement.

 

[Calle1]

The fluid looks good and the ABC error message goes away when the car is turned off and the fault code only remains as "STORED" in Star.

Also the Star tests seems all fine. I'm not an expert but I believe the values are good?

I guess I'll just have to start with replacing the front lateral and horizontal acceleration sensors as the problem seems to be in the front.
Does any one have the MB part number for those? I found this site but I'm not getting any results when googleling the numbers:
https://nemigaparts.com/cat_spares/epc/mercedes/1/fg/230454/65P/54/785/

 

[Craiglxviii]

First one I googled from looking at your Nemiga link returned this:

https://www.fixparts-online.com/en/mercedes-benz-acceleration-sensor-a0009056502.html

 

[ajlsl600]

Accumulators . 1 or more my guess. Diaphragms shot and fluid leaking past.yet no exterior leak seen and dont think that will show a code.DONT let pump run dry .expensive.

 

[ajlsl600]

Might show up on star if system put under stress wid"rodeo" ?

 

[alexanderfoti]

yes, as above, all the numbers will be normal unless is actively jigging about. It will be very hard to confirm the source of this fault Have you run through the accelerometer tests and not just looked at actual values/current faults?

 

[ajlsl600]

Stand to be corrected but faulty sensors,in themselfs are not going to explain fluid loss? Which seems to be a big contributing factor in this issue no ? My maybe incorrect,? Tis my understanding.,when accumulators screwed ride becomes like stranded whale thrashin about .

Unless good leak found around ,near where some kind of ,pressure , sensor is installed ..

 

[Flyinspanner]

That’s why I thought one of the spheres may have “popped” its diaphragm, the fluid would drop as it now takes up the space where the nitrogen once was. And it may have made the handling a bit “squirrely” for a while.

once you check pump pressure it would read ok.

may generate a transient warning (if you happened to be looking) for the pressure drop until the pump built it up again.

if it was a leak to atmosphere, you would have lost more than 6oz when it’s at 195bar. it would empty the system well before 15 mins were up. And you wouldn’t get a decent pressure in the system after.

The ‘accumulator’ spheres - think there are 3 one at the rear valve block, one at the front, and one at the pump called the pulsation damper to even out pressure ‘shocks’. You may need to take off an under tray to find the rear one.

 

[alexanderfoti]

yes actually quite possible above, but would have probably absorbed approx 0.3l of fluid, but the system will be full of after a sphere fails. It tends to blow fluid out of the breather then leave a lower than normal level. It will need bleeding with star to get all the air out and see if the behaviour goes back to normal, if so I would change all accumulators.

The pulsation damper on the outlet of the pump makes a groaning noise when failed, the others do not.

 

[ajlsl600]

When I ""fail "" I often make a groanin noise myself !
My money on accumulators esp if u top it up and level goes down with no visible leak. .op plse advise when resolved n good luck.

 

[LostKiwi]

I think any ABC failure is accompanied by a groaning sound, just not from the car!

 

[Calle1]

Thanks everyone!
The accumulators makes perfect sense and explains the fluid "loss".

I'll get a pair of Cortecos from autodoc as they are only 122 each.

It's a high milage car (22k miles) so I guess it would be time to change them anyways.
However it has been flawlessly maintained by an elder german gentleman who had it before me since new.
I've had it for almost four years now and this is the first ABC problem I have ever had so I guess I'm lucky.

 

[alexanderfoti]

Only for the two, don't forget the pulsation damper and the return one.

You will also need to flush (pitch) 12+L of fluid after rodeing 2x as the failed damper will have filled the system with rubber parts.

 

[Craiglxviii]

Thanks everyone!
The accumulators makes perfect sense and explains the fluid "loss".

I'll get a pair of Cortecos from autodoc as they are only 122 each.

It's a high milage car (22k miles) so I guess it would be time to change them anyways.
However it has been flawlessly maintained by an elder german gentleman who had it before me since new.
I've had it for almost four years now and this is the first ABC problem I have ever had so I guess I'm lucky.

22k is NOT high mileage for ABC. My CL is on 179k and hasn’t seen anything like this...

<dons helmet, ducks into trench and awaits incoming>

 

[alexanderfoti]

Not hight at all!

But age kills accumulators, and ops are 19 years old!

 

[Calle1]

I realize that I left one 0 out.
Should say 220k

 

[John Laidlaw]

I reckon op has missed a 1 before the 22? ie 122k
Anyway as said age won’t help...
Parts available here...
https://www.abcspecialist.nl/en