i got this message this week, I scanned with DAS tool, the pump not producing enough pressure and the systems detects a leak between the pump and valve block line.

so now i'm not sure if to get the AMK Pump or the Arnott

 

i replaced my pump and it cleared all the Errors/Leaks/Codes

 

Just goes to show you that troubleshooting airmatic is really a visual and aural game - don’t trust DAS to tell you exactly what it thinks is going on. Go look at the line, listen for leaks.

it may well have been just a weak compressor that wasn’t putting out enough pressure to test the line - so it also then thinks you have a leak.

or did you find a leak?

 

OK...let me join the discussion. 2008 GL550 175,000 miles. So far have replaced all four struts, the compressor, solenoid valve/valve block, springs and bushings. Still getting the Airmatic malfunction message. What's left to check here? I'm getting frustrated and am out of ideas. Ride height seems normal. Any ideas? Thanks.

 

Level sensors failed? What code is causing the message?

 

Has anyone ran into this issue? I’ve driven our GL550 a handful of times with a cargo box on, and on this recent one we had the “ride malfunction” error pop up. I took the car to a recommended shop and they ran tests on the car and found I needed to replace the yaw sensor and one of the speed sensors (both were causes errors and faulty). They replace the two parts, take the car for a test drive, and ride malfunction still pops up…finally they decided to try out and remove the roof box. They take the car back out for a test drive afterwards, and no ride malfunction error.

I’m curious if anyone’s been in the same situation because it’s weird that a roof box is causing the airmatic malfunction error on the car.

Air compressor and rear suspension air bags were replaced less than two years ago.

 

I'm curious about the errors or logic which pointed to the change of the sensors.

I don't have a box, but I've hauled 2x4×10 and 1×6×10 on the OE airblades (look similar to the air blades Thule makes) and had no issues. Make absolutely sure that you cross bars are located where they are intended to be mounted on the rails. The front location is marked by two barely visible indents. Better observed in shade than in direcr sunlight on the chrome rails. See photos below.

Troubleshoot by moving weight around the box and see if the errors come back. Are they the same codes and components?

How much is the total load of the box and cargo, hopefully not over the intended limit of the rails/bars. IIRC, 90 lb.



Rear crossbar

Front crossbar installed beyond the intended mounting point. I do this to lower wind noise when the sunroof is tilted up. Not for use with loads.

Mounting indicators for the front crossbar. The bar ahould be equally between the indents. Indents are visible on both rails (front to back rails supporting the crossbars.)
visible indentations on the inside of each rail. Just past the sunroof's glass. The sunroof should tilt w/o any intrusion from the cross bar. The rear is mounted in the little "window/gap" over the rear door.

 

absolute horse****. It’s not the roof box, it’s the added weight it enables you to carry, which accelerates the leaks that are in your system.

Your 550 has ADS, the fault is in the struts, the sensors or the wiring harness.

 

I use a rooftop cargo box a couple times a year. Mine sets right on the roof (it gives it more contact points than using the bars). But I would estimate that I put about 200 to 300 pounds in there. My wife likes to take a lot of things on vacation! I've never had an issue with that. I've carried more than 90lbs on the bars, too. If that's truly the limit that MB specs, that's crap. 90lbs is nothing.

 

The error only comes on when I’m driving on the freeway, and the car seems fine after being parked overnight (doesn’t sag down). So I don’t know if I just have a small leak from the struts. I thought it was my compressor giving out again (I just got an Amazon brand replacement)…but when the shop did the tests, the compressor activated fine with no overheating or errors.

 

Do you think this jives with the speed needed to lower the car? I wonder if the level sensors are hanging up? Maybe try popping them off, inspecting, cleaning, grease and reinstall?

 

Yeah I can't see any way this would correlate to a roof box, they have to be missing the actual issue.

 

I do not agree with that. The basis is the connection to the original diagnostics. I emphasize the original diagnostics. Because with the original diagnostics, anything can be checked and controlled. I can drain and fill each silencer separately. At the same time, monitor the height of all shock absorbers, or separately with an accuracy of 1 mm. I can only test the compressor and monitor the pressure in bar. Be careful not to say that I do not need hearing and sight. Diagnosis itself can also refer me to visual and auditory control. With the help of soapy water you can see a leak that cannot be heard. The problem is if the technician can connect the diagnostics and only load the errors. And it can erase errors. It cannot perform a variety of airmatic tests. He won't help you much. Not even non-original diagnostics that do not have these functions, or have only a part of them.
The reason for my disagreement is that it is often a calibration error. Then you can have ears like a hare and it won't help. as well as for problems with the height sensor.
It happens that one height sensor "stays hanging" value. The car inflates normally. If you take a meter and measure the height of each wheel - you will know nothing. Everything will be okay, because only the value remained hanging. It wakes up when you start using the diagnostics to operate the damper manually. You can see which sensor it is right by the values. Sometimes the height sensor really jams, for example 3 mm below the correct value. Sometimes it can be repaired, sometimes it needs to be replaced. There are repair kits for the air compressor. From basic - WABCO compressor dryer filling and sealing. Up to different seals depending on the vehicle type. E.g. Repair kit for air compressor piston AMK Mercedes S, R, ML, GL, CL. It is also possible to buy a Compressor cylinder Wabco V1 nrbo V2 etc. If a small pressure is detected in time, all you have to do is replace the seal on the compressor piston. It can be understood as a piston ring = it is rubber. Always replace the dryer. If the system reports a fault, there may be no DTC. You need to find out by the actual values. I also do this by removing the compressor relay so that it does not blow out. And in a few hours, sometimes minutes the defect can be better seen. Therefore, always connecting the original diagnostics is the first step - if it does not immediately identify the fault, it will lead you to it. Of course, hearing, sight and nose are the diagnosis of any good technician. Take the situation that you do not connect the car to the diagnostics. You measure the height with each meter on each wheel. You will find that, for example, the right front is 1.0cm / 10mm / lower. What will you do next without diagnostics?
Image: basic repair set. Dryer only. Repair set for S, R, ML, GL, CL. Set for w211.

Image: Cylinder V1. Cylinder V2. Check valve + compressor spring

 

Just wanted to give an update. I had to drive the car from SoCal back home to NorCal with the error message on. Loaded with the fam, roof box, and luggages.

I set the ADS on sport mode, that way the suspension was still stiff and it would minimize the stress on the airbags. The car was definitely sitting lower than it should and I was worried the whole drive of the “error, vehicle too low, stop driving immediately”. Fortunately the drive was uneventful.

I took it to the shop as soon as we got home the next day..and sure enough, it was the air compressor causing the issue. I don’t know why the damn thing worked when the shop in LA was testing it. I’m guessing it had just enough juice for one last hurrah, then finally gave out.

The car seems fine now after burning through my wallet between the “repairs” done in SoCal and the repairs done back home. Hopefully that is it for now.
This car has given me more headaches than any other car I’ve owned…but we still love it 😂

 

FYI This compressor tested OK in DAS.
but it was noisy and would not raise the car to its upper position (non-EORP).



why? Because half the pressure it was making was dissipating out the back end due to a failed end cap bolt.

 

Holy moly, the bolt broke?!?

 

Yes. It yielded until failure in the z-direction (EDIT: nope, fatigue crack - two very different failure modes.)

or broke, in plain English.

this bolt having failed was the root cause of my airmatic system being unable to raise up, and becoming very noisy.

when I ran all the tests in DAS, everything tested OK.

get your eyes on the components and see for yourself, or listen for leaks.

 

Wowee. Did it break inside where it was threaded into the aluminum pump housing? Or just outside?

I believe that cylinder is just a rotating DC motor, turning in axis parallel to the bolt. Torque on the motor? I wonder if the pump itself seized (or became higher friction) and so the whole motor housing twisted violently. In other words, the leaking was the cause of the bolt failure, not a result.

 

The failure was in the thread section at pump interface - I.e what was left of the bolt sat slightly proud of the housing and appeared to be a fatigue induced failure now that I look at the picture - the failure is near perpendicular to z-axis and NOT a yield type failure as I stated earlier - which would have resulted in a cup and cone type failure site.
I doubt that pump puts out enough bars to stretch and fail these bolts.

fatigue will do that over time.

 

Good observation.

I would love to do a failure analysis on that pump. Either the bolt was not tightened adequately, leading to fatigue, or it had a defect in the metal, or the pump had some internal failure that resulted in dramatically different resistance to turning - the momentum of the motor essentially twisted the housing.

Remember, copper is a few bucks a pound now. Might want to salvage the windings from inside the motor. And get a peek inside the pump while you're at it.


People say rebuilding those pumps doesn't work. I wonder if that is because of cylinder wall wear. Maybe if the rebuild was done before the pump failed?

Pity MB never figured out how to use the combustion gases to fill the air system, amirite?

 

I am adding a manufacturing defect or a material defect to the analysis.
If the compressor growls, it can be easily repaired. The problem is that everyone buys a repair kit first. The cheapest, of course. Then he removes the compressor and replaces the rubber bands. Unfortunately, sometimes this is not enough / it can be a worn cylinder. First I take out the compressor and look at the extent of the damage. I will order a repair kit or a new compressor accordingly. If there is a problem and it is fixed immediately = just replace the rubber bands. If in a week - the cylinder will be damaged. If in a month - then the driver will have to hit himself on the head with a compressor because he is an idiot.
If I need to buy a cylinder and a piston

 

Interesting. I was not aware replacement cylinders were available.

Replace the motor brushes, too? That's the only other wear item I can think of.

What is the cylinder lined with?

 

.

 

Anyone know how to replace the relay for the aromatic suspension in a 2012 GL 450?

 

It just pulls straight up and out. No tools needed. May I suggest something? If you're asking about how to pull a relay out, you may want to seek help before doing any electrical work - I don't mean that in a negative way, but it's good to know where one's strengths are (and are not) to avoid causing more damage.