Intermittently sagging wagon
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2005 E320
Intermittently sagging wagon
Our 2005 E320 wagon (no Airmatic, just air springs in rear) is intermittently losing pressure, the right side usually drops more . It can go a day or two without a problem, then drops overnight. This morning it was up at normal height all night. Then an hour later with no one touching the car, it was down. I started the car, it pumped up, shut off car-right side drops, I hear a hiss. Leaking bag, right? I started the car again, it pumped up, shut off engine, no hiss and it stays up. Can this be a leaking valve or hose? I can't see how a bag with a hole would act this flaky. I would like someone to explain the system and its valves, lines, etc. I have seen some pdfs but they don't show a schematic of the air path, valves (electric and not), etc. I don't want to buy new bags from Arnott only to find there's a cracked hose or intermittent valve, etc. Also, I note that Arnott's rear air springs for the wagon reuse the old valve-that gives me pause.
Thread Starter
Junior Member
Joined: Nov 2012
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2005 E320
Sags no more!
I installed Arnott replacement springs and reused my old valves-so far so good. I noticed the leaking spring (right side) was original (Mfg date 2004), while the left side was dated 2008 and looked a little different. Replaced both anyway. It took me a while to figure out how to depressurize the springs (both were holding air just fine when I began work)- I applied five volts to the valve solenoids with the main air line under the car at the union that feeds both rears disconnected. The system is pretty simple-compressor applies pressure to the air lines to both wheels, computer opens valves to add or reduce pressure in each independently. A leaking bag will not deflate the other side as long as valves are sealing when car is off. I had a couple of problems with the new springs-the cap on top had the mounting holes drilled a little too far apart-just opened them up a little with a drill bit, solved that. The machined billet aluminum bases of the springs would not drop into the suspension arm-ended up filing, sanding them, even then it took a lot of muscle. Tricked the suspension into thinking it was sagging with a jack and jack stand under each wheel-bags inflated, car driving great!
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Joined: Dec 2011
Posts: 58
Likes: 2
From: Minneapolis
w211 E63
hi can you tell me ware did you get from those 5 volts?
I installed Arnott replacement springs and reused my old valves-so far so good. I noticed the leaking spring (right side) was original (Mfg date 2004), while the left side was dated 2008 and looked a little different. Replaced both anyway. It took me a while to figure out how to depressurize the springs (both were holding air just fine when I began work)- I applied five volts to the valve solenoids with the main air line under the car at the union that feeds both rears disconnected. The system is pretty simple-compressor applies pressure to the air lines to both wheels, computer opens valves to add or reduce pressure in each independently. A leaking bag will not deflate the other side as long as valves are sealing when car is off. I had a couple of problems with the new springs-the cap on top had the mounting holes drilled a little too far apart-just opened them up a little with a drill bit, solved that. The machined billet aluminum bases of the springs would not drop into the suspension arm-ended up filing, sanding them, even then it took a lot of muscle. Tricked the suspension into thinking it was sagging with a jack and jack stand under each wheel-bags inflated, car driving great!
Thread Starter
Junior Member
Joined: Nov 2012
Posts: 30
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2005 E320
I used a 5 volt power supply I had lying around; a supply from an old modem or the like would work. For all I know battery 12V MIGHT work. But if a computer's directly controlling the valves, 5V seems as high as you should go. You don't want to fry the valves-you can't get them except with a new set of MB bags! Arnott's bags do not include them.
Junior Member
Joined: Dec 2011
Posts: 58
Likes: 2
From: Minneapolis
w211 E63
thanks for the fast replay
I used a 5 volt power supply I had lying around; a supply from an old modem or the like would work. For all I know battery 12V MIGHT work. But if a computer's directly controlling the valves, 5V seems as high as you should go. You don't want to fry the valves-you can't get them except with a new set of MB bags! Arnott's bags do not include them.
if i app a 5volt strait to the bag it going to open the solenoid?
Thread Starter
Junior Member
Joined: Nov 2012
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2005 E320
Yes, the wiring to the top of the air spring disconnects near it-there is a two pin connector. I used small test leads. Meter probes would work fine, just don't short them together or you could blow your power supply.
