I searched the forum and didn't find any issues similar to mine. Since the temperatures have dipped into the '20s the air suspension is doing wacky things.
My GL has Airmatic with ADS. I have come out in the morning and have found the left driver side down, on occasion the front of the car will be down. It will rise when it's started. The majority of the time the car will maintain its height until it's started then it will drop down on the driver's side left. On occasion, I can hear air hissing. The most troubling is when driving on the highway, traveling at 70 mph the car will dump all of the air out of both front struts. The ride becomes horrible. It then takes a long time to recover. I am not seeing any Airmatic warning messages. Eventually, the car will rise to its proper height and I can go about my day. Again, these issues are intermittent and only when it's very cold outside. The air compressor has become very loud too, only when it's cold. Once it warms up it quiets down. I don't think it's the valve block, when the car does maintain its height while parked and I open any of the doors I see and feel it rasing to the correct height.

Since I bought the car the compressor would bleed off air often. From my experience as a trucker when that would happen to one of my trucks it was because there was water in the system. I would simply drain the tanks to get the water out. I don't see that as an option on an Airmaric car. As we drove the car more it wasn't doing it as much. Now I am wondering if there is water in the system and it has frozen in the airlines. Has anyone ever experienced that? Are the front struts simply failing and need to be replaced? I'm not sure if the GL has the same brass fittings that connect the struts to the airlines if those are leaking. It's hard to diagnosis if there are no error or warning messages. I am either over-thinking the obvious, but I don't want to just throw parts at it either.

 

The sound of air being bled off is simply relieving excess pressure in the system.

Air compressors get louder as they get old and tired.

You should easily be able to see there are brass fittings there at the air bags, right? It's right there in the engine bay.

Your symptoms sound like classic symptoms, though, of what's been posted many times... one or more failing air bags. One failing bag can sometimes cause the entire front to drop. There's no way for the system to give you an error message and say that "air bag, front/left" or "air line X" is failing. This is where you have to do some basic, good 'ol mechanical/investigative work on your own. You know, the way it's been done for a long, long time! Get in 'there and listen for where the hissing is... use sopay water like I'm sure you've seen discussed in those threads you already looked at (no reason to repeat that).

Why is more prevalent now? Think... what happens to things in the cold? Also, when a bag has a small tear, will it fix itself or just get worse over time?

The compressor has probably been working harder (and wearing out sooner) for some time, now, trying to keep up with a slow leak that is getting worse and worse.

 

I agree with everything you said. Most likely it will be the inevitable replacing the struts. I was ricing them out and holy cow prices have more than doubled since September. I purchased a rebuild set for my S550 through Rebuild Matertech. They sent me a rebuild set and it was $279.00. Today They they are $559.00 They weren't offering a core buyback, but I sent them back anyway. I would rather let them have them and rebuild them and let someone else get them that's in need than throw them away. They do no one any good in a landfill. I was looking for a set for MY GL and they don't have any to sell. They have to be sent in to be rebuilt.

On Rock Auto Arnott is $476.00 per strut.
Cardone $405.00
Blisten is $440.00

I shudder to think what MB is selling them for. When I was looking for struts for my S Class in September Blistens were up there in price but were back-ordered 6 to 8 weeks. I couldn't wait that long. If I am going to spend close to a thousand dollars regardless of what brand I buy I will buy the Blistens.

 

Bilstein's are definitley good. Arnott are good for the front - do they still have a lifetime warranty since they no longer sell direct? I'm not advocating this brand, but I've had one of these for nearly 6 years now (knocking on wood as we speak)... RMT. They're quite a bit less expensive - or at least they used to be.

Are those prices for air struts with ADS?

Take a look at FCP Euro - see what brands they have in stock - they give a lifetime warranty on everything they sell and their customers service is very good.

 

Yes, those prices are for vehicles with ADS.
I used bought an Arnott conversion kitt for my Cadillac 13 years ago, 4 struts, and rear coil springs. The parts were of excellent quality. The car rode amazing. All these years later the guy that I sold the car to hasn't changed them.

 

A hiss is a leak - not normal
a whoosh is the valve block adjusting residual pressure - normal

a noisy compressor is not normal regardless of outside air temperature.

the system does have brass connectors in the lines, but they’re fairly high up in the system.

 

So now it's just a mess. Today's temps were in the 40's. I took the truck today. The front was down when I started it this morning. I had the hood open and listened for leaks, checked the fittings as best I could, and sprayed them down with soapy water. The truck leveled off. I drove it all day without issue until I put it in sport mode and things took a turn. Now it's not leveling off and I am getting the compressor needs to cool down message. I figured since the compressor was so loud that it was on its way out. The left strut is worse than the right. I'm not sure if the right one is leaking. Never the less I will replace both of them and the compressor. I have some clunking noises when I go over bumps. I'll have the shop I bring it to address that too. Just part of owning one of these fine cars. I did notice once the temperature fell to the low 30's the issues became worse.

 

If you’ve driven the car with the front down over a bump, you now have guaranteed leaks from pounding the bag into itself.

your compressor is also toast from trying to pressurize leaking airbags, likely the front ones.

since you have ADS you need to hang onto your struts if they are factory and not leaking.

Put new bags on those struts, do not trust aftermarket complete assemblies to replicate the ride quality you have with a properly working ADS.

 

They aren't going completely flat. they are a bit lower than sport mode. They will be flat by the morning. I was going to order a set of Blistens. I can keep the old struts, but sending them out to have them repaired while the car sits in the shop isn't an option. Who knows how long it will take..Best case scenario it's a full week. That's if there no shipping delays, parts delays, or manpower delays. Right now everything is delayed. I can't hold up a shops lift that long. I assume you think I should have the new ones rebuilt and hold on to them? I should do the same for the back shocks and airbags too when the time comes? I have been looking at air compressors. It seems the AMK that Arnott carries and FCP Euro carries is made in China. Suncore claims their AMK is OEM made in Germany, but ut of stock. Should I just go to Mercedes and get one? I see a bunch of cheap ones on Amazon but the reviews on the ones I looked at are pretty hit or miss.

I should also add I don't know if my Struts or Compressor are factory original to the vehicle. I have had the truck for about 8 months and have put just about 10,000 miles on it.

 

The Hillarity continued today. Came outside the front of the car down. Drove it to work. The left side is normal height right side is halfway up. The passenger rear bag looked to be losing air faster. I managed to get the car to lift all the way up with the height control. It raised to full height. I shut it off went to lunch and ran some errands on foot. When I got back to the car it was still the same height. No issues the rest of the day. I came home parked in the driveway and watched it get lower and lower over the course of an hour on my Ring Camera.

So now I'm wondering should I just replace the rear bags too. If I'm going to that should I just go all in and do the rear shocks too? What are the symptoms of ADS failure/ wearing out? Am I overthinking all of this!??

 

Start with bags. The rears are surprisingly easy to diy on a jack and stands.

i think you might be not overthinking; but overestimating the service life of airmatic components. They’re like tires or brakes, they wear and fail over time.

What you can do to isolate your leaks is to raise it, then pull the airmatic fuse. The corner that sags first has the biggest leak. If after a day no change, go rock the car back and forth, or re-park it elsewhere. Often the way one parks and the angle of the dangle can make a worn out bag seem ok by sealing up the holes, making troubleshooting a confusing exercise. This behavior is minimized with the car raised as the bag is on its tallest extension and has most of its surface area uncovered vice folded onto itself.

back to you having ads, don’t touch the rear shocks if they aren’t leaking. The fronts will have to come off and be partially disassembled to replace the bags.

 

One thing about my driveway is that it isn't level at all. Despite how even and flat it looks in the picture below, it is a nit wavy de to the incline and the manhole covers. There are two manhole covers and I live at the top of a hill. For years I thought my S Class had leaky airbags and it turned out it was just the way the car sat in the driveway. If I parked on the street that was level it was fine. I'm ordering a new set of Blistens and rear airbags. I'm still not sure where to get the compressor. The AMK Arnott sells clearly states that it's made in China.

 

The good news on that is that if it fails you’ll get a new replacement. It will likely be Chinesium unless they’ve changed their sourcing by the time that one fails.

 

So quick update, Front struts were leaking, rear airbags were not leaking. However, the rear shocks are shot. So, the consensus is to replace the rear shocks. I'll probably replace the rear bags as well just so everything is new. The front struts are in and the truck is nice and level now, and not leaking air. I had the shop order the new rear shocks.

 

Glad we finally got to the bottom of this.

Make sure that they are doing the rear shock replacement by the book if they are charging you the full book time. There is a cheat method that involves ripping off the third row armrests and hot gluing them back on to save the labor involved in removing the inner side panels per the WIS. If you’re OK with having them do that they should give you a revised time and labor estimate based on doing it this way, not the full book.

Also what are you replacing the shocks with, OEM or Arnott or other?

 

As long as they are available, OEM.

 

Recall I did a thorough investigation of this and found the non Chinesium compressor. Look for AMK.

On the one hand Arnott will give free replacements, but the replacement labor is not negligible. If you stay on top of the air bags condition, you can get over 100K miles out of a pump.

 

My 2012 GL350 at 91,000 today showed me a “Malfunction” message on the air ride information screen. I stopped in a parking lot and pressed the button on the console to lift and lower the car. With the car running I lifted the vehicle air bag system and pressed the button to lower the car. After completing the sequence, I noticed the message had been reset. When I drove home, approximately 20 miles, the “malfunction” message displayed once again. While in my driveway I checked the height of the vehicle body to the tires and all for heights were equal. I pressed the lift button and within 2 minute a message displayed “compressor cooling down” and the system continued to lift the the car to the maximum height. I pressed the lower button and lowered the car to it regular height. All messages reset and no usual sounds or hissing. Any ideas?

 

Your compressor needs a new compressor.

 

I was afraid of that! How difficult is it to replace and reinstall and where is it located on the vehicle? What is a good replacement compressor

 

You'll have to clarify that. Not sure what "too much" means - too vague of a description.

But, like mentioned, sounds like your compressor is getting old and tired. Taking 2 minutes to raise the car - and it sounds like you you're saying it still didn't finish? - is way too long. I suspect it's also louder than it should be.

 

Removed “too much” which I must admit was pretty vague! I checked Arnott for a compressor and noticed they carry (2) air ride compressors but it appears I can’t buy a part from them directly.

 

Some time ago they stopped selling direct. I believe Auto Zone and maybe Rock Auto will retail it.

 

The compressor is probably the easiest airmatic component to remove/replace. You don’t even need a jack the car up, but you might want to safeguard yourself with a couple of stands front and back. Crank the wheel full right or full left and remove the inner fender liner of the front drinker side wheel well and there is the compressor in all its glory. It sits on a couple of sprung suspension screws and they are a bit fiddly but other than that it is very straightforward. Again you should not be breaking any other airlines than the feed line from the compressor to the valve block so the car should not sink when you do this.

 

Thank Sir,
I have to admit never being a mechanic, I have always had my local mechanic do this type of repairs for me. I’ve learned on prior attempts to fix things, it costs me more to take my damaged parts in for repairs after I’ve broken it.
My question, what compressor do you recommend and confirming during the removal and installation of the new compressor there should be a loss of air pressure?
Thanks