So I picked up a 2007 S550 RWD for 5K, absolutely beautiful car, has all the options I want, the guy that owned it took really good care of it, and got lucky as the engine is just out of the serial number range for the balance shaft issue somehow. I got it home and started sorting some smaller issues it had (fuses, fuel filter, etc), scanned it with my Xentry laptop and cleared miscellaneous codes to see what would come back. When I came back out the next morning the front of the car had dropped to the ground, rear was perfectly fine and didn't even need to air up at all when I drove it again. So I grabbed my laptop again and started going through the pneumatic tests, at first it said it had a leak between the central reservoir and the valve block, I peaked and the output line from the compressor was barely on, tightened it up and everything seemed happy for a bit and it aired up way faster. Then while I was driving the error light came on and the code was for recovery time too long or something similar. Broke out the laptop again (finally glad I bought one), did the pneumatic tests all over and it said all were good (all were leaking with varying levels of severity, but not bad enough to fail the test) except that A9/1y1 was not functioning properly from the front left level valve, I know this usually means it's something in the wiring or the compressor is just old, but this compressor is from Arnott and was manufactured in March of this year so I don't think it'd be bad already. I went ahead and sprayed the valve block and both front struts all around and didn't have any leaks at all. When all the other struts are airing up you can hear the compressor run, however, when the front left (the one that triggered the level valve error) is airing up there's an audible hissing noise coming from the relief valve while the compressor is running. The noise plus the A9/1y1 code makes me think it's the compressor, but why would the relief valve only leak that bad with that one strut? This is my first W221, but I have had several W220s so I feel like I'm fairly comfortable with Airmatic and it's issues, this is just a very abnormal one for me. If anyone has any helpful tips I'd love to hear it, I've searched several forums and it doesn't seem like anyone has posted the same issue as me.

 

Pro-tip.... Arnott is hit and miss at best. I’d have known to be good used parts before fitting new/rebuilt Arnott products.

 

I actually got frustrated and called Arnott hoping they would have an idea what was going on and to also see if they would honor the warranty on the compressor if that was the problem. The "tech" then felt the need to poorly explain the entire airmatic system to me like I was a toddler. I could believe their products being hit or miss based on that alone.

 

Yep Arnott is the answer.

 

When the car front suddenly goes down over night it means you have air leak.

This leak is either one of the struts or the tube to it.

When front is all down it does not mean both struts leaked. If one is not strong enough to hold the front up then the whole front is down but you should be able to measure which side is lower but if it goes all down then it bottoms out both sides and measurement does not show it. You should be measuring it while it is going down before bottoming out and you should see difference in measurement.

The compressor not being able to raise the car in time limits or overheating is a sure sign of a leak.

 

Ok, Airmatic, one of the things that makes me question why Mercedes' slogan is "The Best or nothing" as this is not always the best. But id have it any day over ABC......

I had to replace a strut on the front of my car and here is how my diagnosis process went:
- Check for VERY audible hissing from the car, if its super loud on a part you can identify then replace it.
- If nothing is jumping out at you check the air lines (as I'm sure you know) they are made of fantastic brittle plastic!
- again if nothing is wrong there, the compressor may be going out. It's just underpowered for the job, literally the size of a shoe box. Anyways, it should have a very quiet humming sound, not like an air compressor you use for your tires. If it sounds like it struggling or the volume of it goes up and down it may be that. If you replace the compressor get a new valve block to, since you're there.
- if ALL of those items check out, get a new strut. I get all my parts from FCP Euro, they gave me an Arnott strut which has been perfect. Only about $5-600 out the door. The job only took 1.5-2 hrs to do for me.

Good luck!

 

Tyler be sure to spend some time in a 222 car with MBC before dismissing it. MB has come a long way from ABC in 220 cars.

 

I defiantly think ABC works great, honestly almost Rolls/Bentley quality, & reliability. When the first ABC cars came out they worked great until they got to be 20 years old. That's probably not to much of a fault to Mercedes but just the fact that plastic & rubber degrades overtime and causes problems with the system. An S-Class or any other high end MB with ABC is likely already a very complex car with lots of other things to worry about. I personally would not have patients to deal with it once it starts leaking everywhere, and it will, just like air suspension does.