On purchase of my 04 E320 wagon the air pump was bad, blown fuse and no air. Somehow it was pumped up and took months to bleed down and now has a great Arnott pump, good fuses and now four years later at 180K miles it has bleed down, only on the right rear. The shock that gets all the potholes. But sometimes the bleed down is rapid and other times, (so I know its not the air bag) it will hold beautifully. I just went for coffee and it bled down strongly pumping every 20 seconds and then stopped leaking and now its sitting just fine for over an hour.
So in my analytical thinking this MUST be a bad check valve that is failing to work and hold pressure, then it grabs and does the job. A bad bag would always leak, and electrical issues (are the check valves electrically actuated?) And there is a check valve in the shock and also on the air bag?
Anyway I have the foxwell scanner that will actuate the air system and supposedly operates left and right sides. Releases pressure and lowers and raises the car...Anyway I almost sent for air bags but I see its not that now after it 'fixing' itself. And Its gotta be check valves Im sure, just the right rear...Help diagnosing and repairing the bugger? I know the experts out there are on top of this symptom and thanks so much for your wisdom and experience..

No check valves except maybe at the air pump. Each corner air bag or strut has 2 solenoid valves on the w211 one to fill and one to release pressure. Perhaps a solenoid is sticking??

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Thanks Dieselbenz,
Yes, then it must be one of these and to my thinking either valve, if stuck open or leaking would cause bleed-down. I'll see if I can locate them and also operate them repeatedly with the foxwell which will both fill and lower the shock perhaps to get them working better. I wish I could just shoot them with penetrating oil to perhaps dislodge a particle that might be causing a leak and stuck in the orifices under the valve seal..The right side by the battery has always been a bit lower and when I jack this up then I hear air venting from the front shocks.
Its a sunny day and we had a peaceful election, fingers crossed that these two awful wars can be de-escalated! God help us all...As Rodney King said, cant we all just get along?

So running the foxwell I find it cannot control L/R independently, ECU does not support that. It raised to a crazy height and I thought it would blow the bags but nope. They hold but seem to still be low on the right rear and I cycled repeatedly and will see if it helps. Looks okay right now. The major fill which lifted it to SUV height with about four inches above each tire should blow out any crap, corrosion or particulate, caught in the air valve on lowering!

OK narrowed to solenoid valve for the left rear shock as the leak-down source, but now Im asking if the vent valve is in the shock or the manifold block. Im imagining the air bag solenoid is internal to the bag where the wires plug in, and the other solenoid is in the block. And the valve causing the leak could be either one, the fill valve or else the vent valve. It seems either one might cause bleed down. And to replace the one in the air bag this means replacing the bag.

So no wonder the first step is often to just replace the solenoid block with the manifold. Seems likely..

Following this thread. I'm in the early stages of troubleshooting a small leak on the GL450.

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Jim

thanks engatwork, My car sat fine overnight, no bleed down. My next step is to spray and check the fittings at the manifold block and then all the lines. It did seem to help cycling the solenoids with the foxwell code reader and filling/deflating the system. I'll post the cure if I find it.
My system really bleeds down quite quickly when it does but then at times not at all. To me this indicates a sticky solenoid.

That is what it sounds like.

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Jim

A fellow from Benzworld did the troubleshooting and ended up at the tee fitting of the junction near the rear axle and located his bleed-down leak there. So in that case it was not a solenoid, and I suspect in mine it will either be here or at the manifold in the engine compartment..Currently getting a slow bleed down only on the left rear as shared..This afternoon when its warmer I will get after it! And the mechanics make plenty without our funds helping them, these forums are a great example of free, supportive and voluntary community which benefits us all.
Im kind of a 'lefty' and I enjoy sharing the idea of co-op work like the Amish barn raising that is practiced in traditional cultures world wide, but we call it 'socialist' and outlaw its mechanisms. (no offense to good hearted conservatives)

Tee fitting? Well to my thought the leaking fitting would not be so intermittent but a sticking valve would be, I suspect as the air pump wears that it sends debris into the lines and it can block the valve seat- sometimes. And since the manifold valve body is nearest the pump that would be my candidate for replacement. Hopefully learn more today..I just dont feel that a leaking tee fitting junction would at times hold perfectly well as this thing is now behaving.

We replace air suspension parts pretty much on a weekly basis. Especially on the GLs. Even intermittent leaks from the air springs are common. Sometimes the rubber may fold over the leaky part and sometimes it may not. Been through this hundreds of times. I would replace the air spring. For it to bleed down anywhere else is very uncommon.

That may very well be issue I have. As long as I don't "raise" car I don't get warning regarding leakage. Vehicle is at around 220k miles. All air bags were changed at around 100k miles and I replaced both front bags with Arnott bags at around 200k. May be time for rears again. I'll test folds on rear bags.

When the system is working correctly nothing rides better.

Thanks for heads up.

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Jim

Thanks for the tip Paul Roberts. So Im assuming one of the air solenoids is in the air spring, right where the wires plug in. And then if you replace the spring it includes the solenoid too. Probably not possible to replace that solenoid separately from the spring. I see these very reasonably priced by import mfgrs and it seems they're often Arnot style with no reservoir tube.

Anyway I feel in my case after messing with it a few days that it is the solenoid because after doing the raise/lower and setting the ride height a few times its now holding fine, no leak. And as I noticed before the 'fill springs' command sent the car to the limits of the travel WAY up and if that doesnt cause a leak then its not in the air spring..And in fact the higher pressure could help reseat a sticky solenoid. It bled down last night and then pumped and held today and continues holding.

I would suspect in replacing the bag the issue may often be the solenoid in fact but as a commercial shop its just smarter to get it fixed and not worry which it may be..

That's probably what I'll end up doing but for now Im good and just fortunate I had the code reader to actuate the system repeatedly. With no shop or hoist its a rough job to tackle, although very manageable.

X2

The air springs don't have a solenoid in them. The solenoid is separate from everything else, downstream of the compressor. It supplies air to the air springs via the air compressor. They rarely if never, leak. They usually have one of the ports that fails to deliver air when they go bad. The airmatic system on these is pretty simple and easy to trouble shoot if you have the right scanner. I would replace the air spring.