rich1552

The system designers dropped the ball. I love my 2001 S430. It is easy to work on and a joy to drive. I bought mine a couple years ago with 93K on it. Seemed cared for compared to many I looked at and so far it has been a reliable good looking ride. I do what I can myself having been a mechanic back in the day certified in various areas including brakes and heating A/C. A long time ago but it's something that never leaves you, the knowledge and curiosity and willingness to get your hands dirty. I cannot afford the stealership. So I am somewhat qualified to make the statement that this system ranks right up there with Renault brake systems when it comes to durability and longevity.
6 months after I bought my S430 I began to notice the car sitting lower, and lower and lower. Before I did anything I did research to learn what I could and spent lots of time reading posts here. Very helpful. But not all the hints and tips(well meaning I am sure) were from someone with a good understanding of the system. I had to wade thru a lot to glean some accurate advice. I settled on the diagnosis of my compressor being bad. I shopped and decided I would take a chance on the cheapo Chinese one for little over $200.00. I removed my old one, which looked like it had been put in not long before maybe 2 or 3 years before. Through in the new Chinese unit. Problem solved. Car pumps up to normal height, ride and faith restored. Operation normal. When I exit the car I wait to hear that slight hiss which tells me my 6'2", 215 lb frame exiting the vehicle has sufficiently affected the sitting height that the rear (rearly placed only as it is meant for overall ride height) load sensor has communicated properly the the car is sitting too high now. It hissed a few seconds settling into a new pose until morning.
So why am I dissing the design you ask? Glad you asked that. I have a good answer. As most of you know when air is compressed enough, water is released and converted to solid form or more accurately a liquid. No longer gaseous. Mercedes engineers, knowing this, have thoughtfully included a desiccant chamber in the intake after the air/gas filter. It is mounted atop the compressor motor. It's purpose is to remove moisture from air entering the compressor to prevent distribution of water to things like the valve body, reservoir tank, and of course the shocks. I contend it is a wholly inadequate system unless you live in mostly arid climates. Here in New Jersey we get lots of rain and lots of high humidity days. After installing my new Chinese compressor I decided to have a look see at the internals of the failed unit. I found the desiccant chamber laden with water. It was so bad it made it;s way into the body of the compressor motor and dissolved the varnish on the armature windings and stator casing rust and other disgusting things to form and grow halting all possible movement. Water, if allowed to get past the final protection offered by to desiccant, will be sucked and pushed into all parts of the electric motor and cause failure.
That experience was in Spring of 2015. It is now September 2016 and again my Airmatic is acting up. It has been riding high for a week, almost at the top of travel. I have not been hearing my comforting hiss 'on exit' so I knew something was wrong. The Chinese motor has exceeded my expectations by lasting almost 17 months. I knew what I would find when I dropped it and began tearing into it. Sure enough, bad design is drawing attention to itself again. This time I took some pictures. I tore it down, got rid of the crappy water soaked desiccant and re-assembled with new. I threw it in and everything returned to normal. Ride height and hiss have returned. I cannot really say anything bad about the Chinese unit. As with most of their stuff shortcuts are hidden. In the picture you can see how nasty the spring got when surrounded by water. The German spring was untouched by corrosion so I used it instead of the Chinese spring.
This design flaw, and it really is a big one, is probably causing at least half of all the symptoms I read about here. I am sorry if I offended anyone by disclosing this flaw. Oh, no not really. It needed to be said.

One other thing. If your Airmatic system does have a component that is leaking, even very slowly, not addressing it causes the compressor to put in overtime compensating for the continuous loss. Pushing so much air through overwhelms the intent of the design. It was not designed to cope with constant intake of ambient air due to a leaky shock. I got 17 months out of my Cheapo Chinese unit before needing to purge the dryer. Your mileage may vary.
I feel confidence that my Airmatic is functioning properly when 2 things occur. I hear that lovely hiss when I exit the vehicle and number two is observing the filling action by pressing my ride height button and watching the car rise, see-saw fashion. It should return to normal ride height in the same manner.

The gunk all over the brushes is what remained after I clean them off. You can see the magnet on the bottom in the picture of the housing has been pushed away from the outer wall to make contact with the armature. When I cracked it open it was full of water. All I can figure is there was a freeze and thaw condition that popped it loose from it's mounting. No way this was gonna be back in service. The particles all over the brush mounts was magnetic gook.

It took me 3 hours in my driveway using ramps. I think I'd prefer taking the whole assembly out in case water damage was more extensive to be able to really inspect it. Youtube has some good vids on removal.
Water invaded the bleed down solenoid also which is why my car would not come down. I blew that out, made sure the plunger was free to move. I suspect 85% or more of the situations complained about here are the consequences of this bad design. I am working on a solution now to add a buffer before the compressor desiccant canister so you can visually see the color of the desiccant and change it out. I strongly believe the stock factory desiccant is compromised within months if not weeks and if it was properly designed to address real world conditions the airmatic would not have the bad rep it has now. The compressor is constantly active, making adjustments as you drive. Exit at night, the car lowers itself (the hiss) but get in in the morning and the compressor runs to replace what was lost as the reservoir adjusts your driving height. If you are down on your stops and begin filling the system, you will see your car lifting see saw fashion, not left front, then right front as some have said. It fills either front or rear first then alternates back and forth till proper ride height is achieved.

tusabes

Awesome detailed thread , I don't think we have had anyone examine thedessicant

Yes we start seeing a lot of complaints in the winter , usually from the east coast , when water in the system freezes and valve blocks stick open causing the car to drop

In California Florida and Southern states , where 75% of these cars are its not an issue

ItalianJoe1

Nice write up. As a tech who currently works at Mercedes, I agree that they don't put much lifecycle thought into the systems. I really feel, and this applies across all the German brands, that they get to the point of "this will work" and stop engineering right there. Japanese manufacturers generally build things that are much more durable, the Germans seem to think that as long as you service it as needed, then it's fine. No matter how ridiculous the interval seems. Airmatic, ABC and some of the other very complex systems just have such glaring weaknesses, like the dessicant as a dryer, which as you show just can't possibly keep the air dry under normal, daily use.

Welwynnick

That's the best first post I've read in a long while.


It makes ABC sound well engineered.


Nick

rich1552

Thanks guys. Please don't get me wrong. I LOVE my S430. It is these little flaws that drive used car prices down to where I can afford to purchase it without worrying about going bankrupt. I can do all but the very complex and that work requiring a lift. To be honest this is the finest car I have owned even if it is 15 years old. They are a bargain.

tusabes

Exactly , in a strange way it's good these cars have these expensive issues because if they didn't , they would still cost $15000 used

Is the fix you are engineering something like the compressor air filter , but filled with dessicant? Something external that you can pop on and off when it fills with water ?

For example could we just use these instead of the gas filters typically used as compressor air filters

rich1552

What I am devising is a 3" diameter by about 6 or 10" long clear cylinder filled with color indicating desiccant crystals mounted in 2 straps attached to the top of the radiator mount. It will sit between the mount and the WW fluid/coolant containers. It will tuck in there nicely and provide instant visual notice that you are about to suck water. I intend to make it a serviceable unit allowing owners to refill with desiccant on their own. Each end will have a hose fitting allowing hoses to run down and connect, one to the fuel/air filter and one to the compressor inlet. There is no directional flow imperative at work here. It simply doesn't matter. No clamps should be needed as there is no pressure at either end although I may source and include some anyway.
End caps will be machined by me at first, later outsourced to make them prettier. I was trying to design one to mount right on the compressor. It was too difficult and costly to engineer plus the advantage of popping the hood and glancing at your protection level would be lost. I am also testing a bluetooth module that sits in the middle of the desiccant and communicates humidity/temperature via app.
It's gonna look good and do good. I have no idea about cost yet.
The amount of desiccant used in this system will be at least 5 times the amount the factory offers.

kajtek1

The drier is design to catch the moisture from air entering the compressor and dump the moisture out when the air is released from the system.
But with any leak you will have more wet air coming in, than dry air removing the water.
That happen on my W211 where new compressor piston ring ($16 on ebay) solved the problem for few months. Taking drier apart after few months I had it dripping wet and that was done during one of driest California summers!!!
But doing the compressor rebuild, I installed T on the tubing with pressure gauge. That allows me to monitor small leaks that computer will hide from you.
So 2nd time I hook up my shop compressor to the system and quality time under the car show me pinhole in the tubing right above the differential.
The tricky part was that it would hold 100 psi, would start leaking above, but would take whole compressor output at 140 psi.
I am considering purchase of W220 project tomorrow.
I think I'll be safe starting with $800 price?

rich1552

I am unable to identify any mechanism that drains the water once it gets past the drier. It appears to me that once the drier is saturated the compressor is actually pushing water soaked air through the valve body and then into the 4 shocks and holding tank. I am certain water is slushing around inside the ballast and I am also fairly certain there is no way it can be flushed since it is simply a tank and lacks a drain hole. I have several compressors at home and at work and they all must be drained periodically. The water does not ever seem to reduce in amount, only grow. I might buy a used one to replace the one in my car but not till after I have pulled 29.5 inches of vacuum on it for about 30 minutes. Your experience only confirms my suspicions. You, in dry Cali found your drier full of water. I never goes away. There is no place for it to go. Shouldn't call it a drier. Call it a collector.
Good luck with your purchase!

kajtek1

You are right that the drier under presented circumstances becomes collector, but than we are talking about leaky system.
Would we not have leaks, the compressor would work for very short periods to start with and the back-flow air would push the water outside.
The drier design itself might not be bad, but the computer controls that hide the problems before they become disaster are.
Now - after I fixed the small leak, my system holds 120-140 psi overnight and if the compressor comes for few seconds once a week, that might be all.

kajtek1

BTW don't know if you noticed, but the same exact compressors with the same driers are used in all luxury cars.
Maybach, Land Rovers, BMW, Jags
I wonder how many airbags are exchangeable as well.

rich1552

Correct. They are on many European and American luxury vehicles. Although never considered to be a serviceable item, assembly constraints allows them to be disassembled if one is so inclined. I will be addressing the W220 first, then others with a supplementary underhood mounted drier with high visibility indicating crystals which when installed should be done in conjunction with a cleanout of the compressor mounted drier. That way you know the system is getting a fresh start.

kajtek1

When there is no such thing as too much air filtration, I would put installing pressure gauge on the system as first priority.
Extra drier will help in dealing with the results of leaky system, but will not tell you about the troubles.

wallyp

While the larger, more visible drier is a neat idea, I don't think that the situation is quite so dire on most W220 cars.

If the system doesn't leak, a small amount of outside air will be pumped in perhaps once or twice each time that the car is driven. The drier will absorb (or adsorb) most of the moisture in that air. When someone leaves the car, or weight is otherwise reduced, that dry air will be released thru the drier, removing most, if not all, of the moisture.

If the system leaks, make-up air will constantly be pumped into the system, adding some moisture each time. The system air will still be released thru the drier, but in such a small quantity as to remove only a small part of the entrained moisture.

If the design was as faulty as proposed, there would be very few 100,000 mile-plus W220 cars on the road...

rich1552

Please correct me here if you think my understanding of the system is flawed. The air pulled into the compressor does not pass through the drier. It goes directly into the compressor piston, gets compressed and then passes through the drier, to protect systems downstream. My contention is the air being compressed overwhelms the drier too quickly in some climates and forces water laden air into areas it should not be allowed. My idea will offer considerable protection, if one pays attention to the little crystals. Compressing dried air is preferable to compressing whatever the day brings.
There actually are very few W220's on the road these days and the notoriously unreliable and expensive to fix airmatic system is the main culprit driving the resale value of this fine automobile into the dirt

Jack_88

I think Wally's point was that despite this possibility, it must not often cause a problem due to the apparent number of higher mileage S-classes on the market. When I was shopping, I found a whole lot of them were at 140k or more. It was hard to find a lower mileage example. I also think it's a great point that unless there is a leak, very little outside air is actually introduced with normal use, so the drier wouldn't have much reason to get saturated. Unless there is a slow leak.