W205 C-Class C350e Estate Airmatic Suspension Issues (2016)

[WordSmith]

I was hoping someone may be able to help me figure out what's causing my suspension to be shaky.

My C350e is 45 months old this year. Almost 60,000 kilometers.

About two weeks ago, the ride home from school with the kids was rather bouncy in the back. There was no warning light on the dashboard. I had to pull over to make sure the rear wheels weren't touching the ground. First impressions were favorable. After turning the key again, I climbed back into the car, and the dashboard screen showed that the vehicle was in motion. The suspension returned to normal, and the trip home was uneventful. I was quite comfortable going out later that night.

On the way to school the next day, I saw a warning that said "STOP VEHICLE - VEHICLE TOO LOW" displayed on my dashboard. Before I could stop, it was gone, and when I finally did, the front and back suspension seemed unharmed. The fact that the automobile continued to function normally while the alert was shown makes me suspect that it was a bogus message.

Back became quite bumpy, no warning sign, but rear suspension low (wheel arch over the tyres), same as the previous evening on the way home from school. When I hit the suspension up button and began driving again, the vehicle once again rose. The compressor engaged as expected, based on my hearing.

Since the suspension remained in its normal position when the vehicle was parked from Thursday to Tuesday, we can rule out a leaking air spring as the cause of the problem. Similarly, I didn't hear the compressor start up on Tuesday when I turned the key to take the vehicle in for fault code reading.

Less than five minutes from home, on the way to the garage, the dashboard warning message to stop illuminated once again, and this time the rear suspension absolutely sank straight down. However, when I stopped and clicked the button to lift the suspension, it went back up and rode smoothly the whole eight miles to the garage.

The back end, which is the part that has been falling, did not register any problems in the code reading. Codes for both front sensors being out of range and an error for the compressor taking too long to increase the height were apparently present.

Based on the symptoms, and that the compressor seems to be working and raising the car, and that it is an intermittent issue, my conclusion (before error codes read) was that it was either a sensor issue - system thinking rear is too high and dropping the rear, but doesnt pick up the change and therefore keeps trying to drop it. This, however, seems unlikely given that the error codes do not point to an issue in the back. The mechanism might have been opening a valve to lower the suspension, but it could have been stuck in the open position, causing the read to drop to zero. The compressor would run too long because it is attempting to raise pressure yet the air it is fed is escaping unimpeded. The fact that the vehicle did not issue a warning the first two times the system voltage dropped too low suggests otherwise, unless both explanations are correct.

The technical data the mechanic at the garage has obtained seems to indicate that the compressor is leaking in some kind; yet, I still don't understand why the rear springs would be deflating in this way.

After being looked at, it ran normally for a day before flashing the stop warning again; this time, however, the front end was the faulty component. I had the codes checked again the next morning and the same three appeared (even though I had already deleted them). Since then, it has occurred a few more times, always to the front or the back but never both at once. When I turn the vehicle off and then back on, I always receive the "car rising" message, and the car always rises again after around 30 seconds, which is about what you'd anticipate given that it's entirely filling two bags.

I have ruled out a leaky air bag or supply line because of the compressor's direct connection to the valve manifold and the fact that it is alternating between the front and rear. Since the air bags all share the same discharge valve, I've deduced that it's staying open for longer than it should, either due to a strike or the controller's insistence on keeping it that way. This is causing the compressor to take too long to refill. The error numbers on the two front sensors are what I can't explain.

In my opinion, this is the kind of problem that may be resolved with the assistance of someone who has encountered the same set of symptoms previously.

I'd be thankful for any suggestions that use logic to connect the cause to the symptoms. If you agree with me, would you put more faith in the controller (despite the valve being a discrete component attached to the compressor, it is not sold separately, necessitating the replacement of the whole unit, even if it seems to function normally) or the valve?

I've heard that a leak within the valve manifold would be to blame, but I don't believe that's the case here; the vehicle doesn't tip over while it's sitting still. If anybody thinks this might be the case, however, please explain how that would come about.

Thanks

 

[TDudette]

My 2016 S205 with 50,000 miles on it fell down on all four wheels and was not drivable, so I had to have it towed to the dealership early this year. The compressor stopped working because the mobile recovery (RAC) team let it run for too long. A flatbed truck took the car to the dealership. In the end, the problem was the car's compressor, so the next day the mechanic came and replaced it along with its relay. There was still slightly over £300 to pay after MB's contribution, even though the vehicle was out of warranty by a year. We picked up the automobile and drove it home, according to the speed limit of fifty (50). After 20 miles, the rider saw a yellow caution truck, slowed to 30 mph, and kept going. After driving for three miles, but still less than a mile from home, the red stop vehicle alert illuminated. Dealer was called, and a second rescue was set up. Although the air bags were a remote possibility, I mentioned that the automobile had a new compressor and that all four wheels had failed. The dealer assured me that the new valves almost never break down (there are lots of aftermarket options available on eBay, so there must be a need for them).

The automobile was ready for pickup the next day, so I did just that. Compressor replacement was discussed; after discovering the problem, a new compressor and its relay were installed. When I inquired as to whether or not the valve block had been updated, I was assured not to worry since the new design is foolproof. When I remarked that it was fortunate that they had two compressors on hand, the service manager said, "We have done a number of them." Since MB components are covered by a guarantee, there will be no fees associated with replacing them. I drove home fearing further trouble, but the vehicle has been running well for the last five months, despite often sitting for more than a week at a time.

In that case, what have I discovered? Overheating or a jammed compressor in a W205 may burst a high amp fuse and relay, and the valve block is disconnected from the compressor, so repairs can be expensive.

Why could I lose traction in the front sometimes, but the back on other occasions? Valve block malfunction? A malfunctioning airmatic electronics box? Is there a problem with the compressor's relay, the pressure relief valve, or the level sensor(s)? It may become expensive if you had to replace components without error codes. What is the approximate cost of a relay (£40), valve block (£70), and electronics box (£300)? And then there's the work. I've rambled on enough, I'm sorry.

[WordSmith]

Thanks. Nothing about this is particularly difficult to do or time-consuming. The error messages do not aid in problem identification. I am not in a hurry to take it to Mercedes since I know that their "technicians" (aka fitters) would simply throw parts at it at my cost and not truly get to the root of the problem but instead "fix it" by replacing everything at a premium price with a ludicrous labor fee.

[Matt865]

Excuse me,

I'm experiencing something quite similar and was hoping you might share your solution. Currently having troubleshooting with mechanics who have ruled out compressor and leak problems. The airmatic failed twice, both times while doing school runs (the vehicle would sit on its wheels and display a warning message). Outside of this, getting the kids to school went well.

In the first instance, all four sides collapsed, but in the second, just the back collapsed. After waiting around for ten to twenty minutes in each instance, the vehicles were able to resume regular operation and go back on the road.

This problem occurs so seldom that the garage can never reproduce it.

[VWDaveBMW]

The same thing is happening to me; the automobile keeps dropping in height as I drive.
Is it working properly now? How did this problem get fixed, exactly?

[VWDaveBMW]

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Edited August 7, 2023 by VWDaveBMW

[WordSmith]

I forgot to inform everyone here. As of the first of December, you will be able to witness for yourself the nature of my problem. I switched out the relay and it appeared to fix it. However, the issue returned more than a week after a new relay was placed. I was able to obtain a replacement compressor pump from Miessler in Germany and have it sent to my address in Dublin within 24 hours. Have had no problems since installing it before the holidays.

It's possible that a new relay (which shouldn't cost more than twenty pounds) might solve your problem if it's identical to mine. Alternately, you might pay extra to have a new relay and compressor installed simultaneously. You must also replace the relay when you swap out the pump on a compressor.

I ordered a compressor pump from Miessler Automotive, and I'm quite pleased with the service I received. I was amazed at how soon everything came and how quickly my questions were handled.

[VWDaveBMW]

I appreciate the prompt answer; I have an extended warranty and think this will be covered.
Using the warranty to attempt a repair.
We appreciate you taking the time to explain this in such depth and bring it up here.

[WordSmith]

After a month of online study, I've concluded that MB should repair this at no cost to me under the terms of the guarantee. MB is aware, as far as I’m aware, that the original Wabco compressors have a somewhat short lifespan.

[TDudette]

After the one-year warranty expired, MB nevertheless gave me a sizable contribution toward the cost of a new compressor. When the dealer has many in stock, you know they sell them.

[jennycarlotta]

Howdy, Farm Boy! Was it a Mercedes warranty or one from a different company? My 2015 C250 is experiencing the same problem. Both the front and back halves fall at the same time. The situation often escalates. After a few attempts, the fog clears up and I'm able to drive normally again. My appointment with the dealer is set for next Friday. Have you had the official distributor work on it? In gratitude