No sagging but Malfunction displays consistently on dash. I’m assuming the compressor is running too much/often!
Should I install a new valve block? Are the elcheapo ones on Amazon worth a try?
I installed four new Arnott suspension units a couple of years ago.

 

Pull the codes, but that error message is generally due to weak output from the pump. Look for, I think it is, 5503 Central Reservoir Taking Too Long To Refill.

 

Where do I find the central reservoir?
Will my I-carsoft reader pick up that code?

 

The malfunction warning on the dash is typically the compressor overheating because its working too hard to overcome a leak. I'd be rulling out all airbags first.

My Icarsoft scanner did pick up the code Eric mentioned. However, my experience with the airmatic is not to expect too many codes when things go wrong. Fixing airmatic systems is a process of elimination. My ML has the reservoir under the back seat.

Regarding your query on Amazon valve blocks, I wouldn't, unless you enjoy buying and installing them over and over. Arnott make one and I'd give that a go.

 

You need to interrogate the Airmatic system with your diagnostic tool. If it gives you that code, it is likely your pump is now weak.

 

Your reasoning on this is not quite right. Generally, Airmatic does not run the pump to adjust ride height. It will do so when instructed to go to off-road height, but in general it uses the reservoir, and refills the reservoir while you are driving, so you don't hear the pump running and can entertain the illusion that it is magic.

I also doubt that Airmatic monitors the pressure while adjusting spring heights, except to ensure that the reservoir does not fall below its lower limit pressure.

The system does not do much of a self diagnostis. For example, there is only one pressure sensor, and that is on the valve block. MB software and hardware engineers tend to make systems that are good enough, and then they quit. That's no good for motors; you have to think, how could this fail, and then work from there. This holds especially true for a supposed off-road vehicle.

GL reservoir is underneath, just forward of the rear bumper.

Amen. I installed a Chinesium (Ebay, but same holds true for Amazon; Bezos reports directly to Xi) valve block that was pure fakery.

Unless you live in a humid environment and have made a habit of running around on deflating springs, the valve block is very durable. It gets roont by the compressor's dryer becoming overwhelmed, and the compressor blowing moisture into the block. Which gets to the core point: Such pumps are good for a certain number of hours of operation, less if they are overheated or suck in dirt. Leaking springs consume those hours quite rapidly. A weak pump usually has a root cause.

 

I installed a new Arnott pump when I installed the four new Arnott suspension units a few years ago.
I guess I must assume there is a leak somewhere in the system.
So, soapy water and a flashlight will probably find the leak, right?
The car rides very well and at the correct height on all four corners and it doesn’t sag during the night YET!!!
Malfunction message (arrow pointing up) has gone from intermittent to permanent.

 

Unfortunately, Arnott sold two pumps. One is Chinesium, with a life, for me at least, of about 30k miles. That was with known good air springs. That pump model number is, if I recall correctly, 3214. The only pump I have heard of lasting is the AMK pump; all of which have a big AMK logo on the side.

If you are in a location in which you can do such work in mid January, certainly confirm with soapy water (lifted suspension, remember) the air springs and air hose connections. The reservoir is such a distant possibility it practically does not merit discussion.

If the pump has failed, and I am confident it has, find out what pump Arnott would send you as replacement; if it's AMK, go that route; if Chinesium 3214, order an AMK pump from someone else, e.g. Rock Auto, and simultaneously get Arnott to send you a replacement, if it's a 3214, and sell it on Ebay. Cut your losses.

 

I don’t want to screw around with this for the rest of my life (80 years old) so I bit the bullet and Arnott is sending me a new AMK compressor. At 160k the tranny, engine and all running gear on this rig seems good, i.e. engine uses zero oil between 10k changes and I just serviced the tranny for the 2nd time. 1st time when I bought it with 90k on the clock. My pervious ‘07 GL450 with lower miles used a quart every 750 miles which really messed with me! I determined it was valve stem seals and I didn’t want to tackle that so I traded it for this ‘12.
My hobby in retirement is to get 300k on this rig or until my Cyberbeast arrives.
Sorry for the long winded story and thanks again for the input from ALL of you.

 

That's AWESOME, you're 80 and still wrenching on vehicles. That's great.

 

Good for you, on all counts. I still would check out the air springs when the weather is agreeable. Do it annually (I am lecturing myself, as I have not checked my own air springs in 30k miles).

 

I changed my original MB compressor with an AMK. I sat then on the bench side by side and carefully inspected them. They are the exact same article, at least externally.

If you're doing the soapy water test, make sure your airbags are fully inflated to the highest level AND the car is resting on its own weight and not on jack stands. It may heed normal pressure to reveal a leak.

 

100%

Also, it has been said before, but since safety is involved: Never get under the vehicle without jack stands present, should one of the air springs blow while you are underneath. Lift the suspension, place the jack stands, then inspect the air springs.

People make a big deal out of not getting under a vehicle supported only by a hydraulic jack, but the air springs are more likely to fail than a jack.

 

Yes, jack stands in place for sure, but with as much weight on the wheels as practically possible. I never get under mine without them (I used to until I thought about it one day whilst under the car).

 

I have always used them religiously after watching Ruthie intentionally release the jack killing whoever (someone she needed to get rid of) was under the car in an episode of Ozark!
I still have nightmares about that scene!!! LOL!

 

It’s the Redneck way to go

 

Repeat, no sagging with old or new compressor BUT
now after about 50 miles with the new compressor the MALFUNCTION message displays again???
If I had an air bag leak I would get sagging in the leaky corner, right?
What’s next???

 

It might be necessary to clear the error code. In general the MB computers take some time (several drive cycles) to reset the errors. This can be aggravating when dealing with a misfire error, which shuts off the fuel injector to the afflicted cylinder; you swap the coil, but the error remains until you have gone through three drive cycles.

You can either hook up a scan tool - I am unclear on whether unidirectional tools such as MBII can clear module DTCs - or just go through the cycles and wait for the error to self clear.

It is also possible you have a leak at the air fitting on the pump, from the pump at the valve block, or to the reservoir at the valve block.

 

That is an error that comes on when you have a difference between the commanded position and the actual position.

Clear the code by either yanking the battery for a couple hours, or a DTC reader capable of doing it, and then see if it reappears.

With a new compressor that is audibly coming on and the normal wishing noises coming from the front right corner I would suspect that maybe one of your level sensors is giving a missing or erroneous input. so whatever position the car is being commanded to take it always reports a different one and that’s when you get the error.

 

Wait, how do you know what the error is? Are there different Airmatic dash error messages?

 

It’s evidently time to spray soapy water on the compressor outlet and on the valve body connections.
where is the reservoir?

 

I wouldn't bother looking at the reservoir. It is unlikely to be the cause. But for reference it is on the underside, fore of the rear bumper.

To check the air line at the pump, you have to ensure the pump is running. There won't be pressure in that line without the pump running. Press the dash button to lift the suspension to force the pump to start.

But you really need to get a diagnostic computer to see what the Airmatic DTC is. As @Max Blast suggested, it could also be "ride height is implausible". I don't know if the dash error messages are different for the different codes.

Or just wait to see if it clears itself.

 

there are two aromatic error messages that I have seen, one is stop driving car too low (I’ve only seen this in a w211) and the other is compressor cooling down with a picture of a car and an up arrow through it.

Both indicate that the car is not in the commanded position whether that be normal or raised.

 

Yeah, you're thinking of "ride height implausible".

There is also "taking too long to refill central reservoir" and "pump overheated".

 

yeah, that on the code side, I do believe the Dash read out only has the two that I mentioned.