Hello fellow MB enthusiasts,

Unfortunately after reading so much at the boards and gaining valuable experience,my first post will be on an ABC issue.I read almost all of the ABC related topics here and on other forums,but couldnt find a case with symptoms like mine.

After a short drive a couple of nights ago,upon parking on a curb and locking the vehicle ABC fluid started to spurt from the reservoir.That was no more than 0.5 liters.After pressure went down to normal and the spurt ceased, i checked the fluid level and it was low as expected.I filled around half a bottle of fluid.At first it showed the red ABC drive carefully warning constantly,then as i cycled through ride heights and turned the steering wheel both sides it disappeared.Then the other day after a 2 km drive to a mechanic it flashed the "ABC drive carefully" for milliseconds when driving onto bumps.The ride expectedly was a bit loose. I plugged it on a Star Machine and it showed "C1525-064 - System pressure too low " stored.At first i thought the pump is going bad.However when performing almost all tests the Star Diagnosis is providing i figured out that the pump is producing 180 bar constantly,and when rodeoing a bit lower 115-130-150 bar.Pump makes no excess noise.I unfortunately heard the unbearable groan of a failing pump in a friends S600,so i think thats not the case.I next observed the ABC reservoir.The level of the fluid was constant either with the engine off or at idle.I didnt check it during rodeo,because i was afraid it will spurt out once again.There are bubbles in the fluid reservoir,which may suggest air in the system,which cant be forced out.Then when scrolling through the star options i messed with adaptations of the ABC control unit and after successfully performing level calibration i proceeded to plunger sensors and it said plunger sensor values are not within tolerance or something like that.That for itself caused a blue "ABC visit workshop",with the error "unsuccessful plunger sensor calibration".I did that only out of curiosity.The car did not drop level, or lean, or sink on one side.I remember these calibration values are hard to guess and it was a pain when i messed around them on my SL55 and my W220 S (although its an airmatic),but i proceeded anyways - stupid me.However just to confirm and again out of curiosity, i risked having an error on the SL's dash and performed a calibration on the R230 with the same values i tried with on the CL and the system calibrated the level sensors and the plungers succesfully - so there must be any fault with the CL plungers or ride height sensors,although i have never experienced a calibration issue or fault on the display before i messed up with the Star afterwards.Next i put the CL on a lifter to inspect for a leak around struts or hoses.I found no such external leaks.I inspected the struts and all but the front left felt pressurized and were very hard to move.The front left shock could be moved by hand as car is on the lifter.Then i tested the strut on the star - actuating the release valve and then pumping it back to level.I think the test went ok.
Although it may be out of the point my cruise control (not distronic) and the speed limiter are not engaging at all (not flashing or working until some speed).I observed that around 6 months ago.It may have been longer as i almost never use it.No fault codes in the ESP module and tested the cruise control/limiter switch via star and it was working.Following the unsuccessful plunger calibration i come to think that the two faults may be interconnected.

I have never done any ABC work on the car since its in my hands.There are no records of ABC interventions in the service book and the invoices i got from the previous owner.I flushed the system when i bought the car 5 years ago at 165,000 km for prevention and got new fluid and cap filter.Now the car has around 215,000 km.Again out of the point, on my SL55 i had an even harder splatter like the above mentioned (maybe 2-3 liters of fluid everywhere in the engine bay)and was prepared for a new pump, as then it was obvious that the pump wasnt circulating the fluid - i had the tuna boat ride,constant "ABC drive carefully".It turned out to be an o-ring which cracked and allowed air in the system.It was a 30$ fix.

Excuse my long post and offtopics,but i want to make all the circumstances clear.Any help and ideas would be greatly appreciated.
Thank you and i wish you faultless and trouble free MB motoring (if thats possible with nowadays Mercs)
Stan

 

You can help this link, some noise is heard?
https://mbworld.org/forums/cl-class-...blems-abc.html

 

Hello Matias,
Thanks for your reply ! I actually read your thread before posting mine. I have not heard any excess noise when in motion,nor when the ABC is raising and lowering. I just started the car and it rises in 5 seconds between levels. Another thing which i noticed just now is that when i cycle through ride heights directly from the lowest to the highest (double click the ride height button), the RED "ABC DRIVE CAREFULLY" flashes for a second.However the car rises immediately without any noises.

 

checking the suspension accumulators
https://mbworld.org/forums/cl-class-...c-problem.html

 

I dont have the syptoms of shot accumulators,which are described.Anyways is there a star test which points out accumulators or any other physical test ?

 

When accumulators rupture, the symptom you are having rears its ugly head.

Check your accumulators.

 

Thanks for the answer awiner,but i didnt quite understand what you mena by "having rears its ugly head".Can you please clarify that.Thank you

 

you get fluid overflow from the reservoir.

 

Yep.I have seen it spurt myself.Now the car will raise/lower no problem,doesnt lower an inch overnight,the pump works at 180 bar,the fluid doesnt or barely changes level with engine on and i still get system pressure too low upon driving on bumpy roads

 

A little update on my issues guys.
I plugged it in again today and performed pitch,roll and rodeo again,observing the live data on pump pressure.The actual values showed the following :

On engine idle : 180 bar without any test car sitting level
On engine idle : Flucutating pressure between 60-200 bar and sluggish pitch,roll and rodeo
At 1200-1500 rpm : 190 bar without any test car sitting level
At 1200-1500 rpm : Pressure still fluctuating but within higher pressure 130-160 bars - quite dynamic pitch,roll and rodeo (as it should be)

When Driving through bumps :
Driving in auto mode (low rpm) going through a bump at 30 mph applying no throttle : drop in pressure and flashing red ABC drive carefully
Driving in 1st gear at 2-3 rpm, going through the same bump at 30 mph : no ABC warning

Cycling quickly through suspension heights from the button - directly from the lowest to the highest :
Level 0 to Level 2 (lowest to highest) at idle (600-700 rpms) : drop in pressure just before reaching Level 2 (and the warning flashed)
Level 0 to Level 2 with light throttle applied 1200-1300 rpms no drop in pressure and а very smooth rise

So what now ? Is my pump no good ? Why is it prone to a drop in pressure when at idle,and not when applying throttle ? Can an internal leak or an air lock contribute to that behavior ?

 

I meant by the 'burping' your reservoir experienced it likely indicates you had one of your accumulators rupture.

I had this happen when my first accumulator ruptured. I didn't think much of it as the vehicle still operated without issue.

I had a ABC beep go off everyone in a awhile, which logged a low pressure code.

I had the reservoir 'burp' again when the second accumulator ruptured. At that time, the car was undrivable due to under pressure warnings and I have to replace both accumulators.

Moral of the story, replace them before they rupture as it will save wear on your pump and associated lines.

 

Thanks a lot awiner.I will have an indy check them tomorrow.He unlike me is quite experienced at ABC.I will update on what happened.The first "burp" as you call it on both my CL500 and SL55 was accompanied by the "tuna boat ride" and constant "ABC drive carefully" was solved by some o-rings (forgot which).I never replaced accumulators on both cars,and i very much doubt that the previous owners have.Anyways i will keep you up to date on the resolution.Thanks once again.
Stan

 

It turned out to be the front accumulator.Although the car was not that bouncy,the accumulator was full of abc fluid.System sustains pressure and i performed calibration with no issues.I consider replacing the other three.My parts supplier only had one in stock.
Thanks for your expertise guys !

 

If one went out the others will be shortly behind. Consider doing it before it burps again :-)

 

I will definitely replace the other 3.I would have done that already,but neither my part supplier,nor the dealer have them in stock currently.I will also replace my fluid and filter as it may have particles from the ruptured accumulator.Thanks once again for the suggestion on accumulators.At first the "ABC master" indy approached the issue by trying to calibrate the plungers (which i came to know is impossible if the system has low pressure).He plugged in different struts and came to the conclusion that my right front strut is faulty.I mentioned him the acumulators,especially the one in the front - and he said "thats the dumbest thing i ever heard".So i went to the dealer and they said "front left strut,right rear strut,and ABC pump".I told them to change the accumulator first - they said they will but there is less than 1 % it solves the issue.The dealer didnt have the accumulator in stock,so i bought it from my supplier (the last piece he had) and changed it myself.After all your expertease really saved me from changing parts which are not faulty.When speaking to both the indy and the dealer i felt like i was much more competent than both of them,eventhough my knowledge is based on reading forums only.What a shame.