W211 rear suspension drops sometimes but not always
- Thread starter 2006e280
- Start date
MercHorse
New Member
Hi all - I'm a newbie reading here lots of MB knowledge and experience particularly around rear suspension troubleshooting and resolution, as I'm experiencing similar sagging rear nearside air suspension on my 2004 W211. It just doesn't seem to want to rise to the correct height. I've been using a Foxwell i50TS scanner to collect data, very useful especially live data, and notice my lazy rear end drops even further during a journey, getting down to -42mm. The system wake up and pressurisation process is important to understand, including what it does during a journey so I continue to learn. For me it's about understanding the intricacies of EXACTLY how the system works, and relating it to what I'm experiencing. A very usefully read here Still got issues on 2007 E class estate rear self levelling air suspension. | Wheels, Tyres, Brakes & Suspension
MercHorse
New Member
Well I'm no further forward with understanding EXACTLY how this system is meant to perform and may never find out but I'm gaining more info and experience as I continue troubleshooting that I've catalogued below for anyone else suffering Random Suspension Paralysis RSP 
:-
I continued troubleshooting yesterday - car on the level, rear near side suspension very low, we'll call it flat. Opened driver door, car wake up on, compressor started, all normal - but no suspension movement. Fudged around getting scanner fitted, ignition on engine not running - rear ns suspension level reading -42mm but still no suspension movement. Started engine - no suspension movement. Opened passenger door...... REAR NEAR SIDE SUSPENSION INFLATES TO CORRECT HEIGHT which I've not seen for months! Foxwell i50TS suspension live data level reading +4mm - so went for a drive fully expecting rear ns to collapse, but it stayed inflated with live level data bobbing around 8mm, which is much better. Got home and suspension level looked level.
That was yesterday, the car hasn't been touched and is currently still looking level but for how long - I'm fully expecting repeat RSP but live in hope.
So, defo a random queer thing happening. I read "poor routine maintenance arrangements for the compressor" particularly related to the inlet filter and how it can disintegrate over time - filter particulate in solenoid valves would defo cause trouble. My compressor is no different, never been maintained I'm sure, and in fact, whilst it runs/works, it sounds like a bag of nails. A compressor service/overhaul will be my next job.
Another cause could be moisture in electrical connections/connectors particularly on my rear nearside airbag.
:-I continued troubleshooting yesterday - car on the level, rear near side suspension very low, we'll call it flat. Opened driver door, car wake up on, compressor started, all normal - but no suspension movement. Fudged around getting scanner fitted, ignition on engine not running - rear ns suspension level reading -42mm but still no suspension movement. Started engine - no suspension movement. Opened passenger door...... REAR NEAR SIDE SUSPENSION INFLATES TO CORRECT HEIGHT which I've not seen for months! Foxwell i50TS suspension live data level reading +4mm - so went for a drive fully expecting rear ns to collapse, but it stayed inflated with live level data bobbing around 8mm, which is much better. Got home and suspension level looked level.
That was yesterday, the car hasn't been touched and is currently still looking level
but for how long - I'm fully expecting repeat RSP but live in hope. So, defo a random queer thing happening. I read "poor routine maintenance arrangements for the compressor" particularly related to the inlet filter and how it can disintegrate over time - filter particulate in solenoid valves would defo cause trouble. My compressor is no different, never been maintained I'm sure, and in fact, whilst it runs/works, it sounds like a bag of nails. A compressor service/overhaul will be my next job.
Another cause could be moisture in electrical connections/connectors particularly on my rear nearside airbag.
MercHorse
New Member
Sad to report today rear ns suspension refused to inflate. RSP troubleshooting continues, when the weather is a little less wet-n-windy.
Wearsthefoxhat
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The filter, hoses and filter holder are a reasonable price from MB. The compressor can be refurbished, a company “ Bagpiping Andy” supplies new piston rings.
If one side is deflating randomly it is likely to have a small leak, sometimes the bellows collapse and seal the leak, sometimes they don’t, as explained to me by a knowledgeable gent.
If one side is deflating randomly it is likely to have a small leak, sometimes the bellows collapse and seal the leak, sometimes they don’t, as explained to me by a knowledgeable gent.
The 211 has a solenoid valve on the top of the air spring itself, and they are never a problem in my experience, so if it’s going down you have a leak in that air spring. The compressor can time out if it doesn’t inflate the air spring within a certain time, and it’s a wait before it will try again. Be mindful that the compressor isn’t designed to keep inflating the air spring from flat all the time, and you will knacker it if you keep doing that with it.
MercHorse
New Member
Thanks guys, I need to check the compressor and the relief valve and over pressure solenoids. Nice to hear the air spring solenoid valves are reliable.
With respect to a leaking air spring, I wish I could get air in it long enough to leak! Most of the time the compressor starts but the suspension either doesn't move or creepy up 1/2 in, with exception of a few days ago (that I wrote about above) where it inflated to the correct height and I drove it around for half an hour no problem. It even stayed inflated for almost 48hrs untill I drove the car the following day and within 1/2 mile the rear ns suspension was deflates again. All this time btw the rear off-side air suspension is at perfect heights.
Nice to hear the air spring solenoid valves are reliable.With respect to a leaking air spring, I wish I could get air in it long enough to leak! Most of the time the compressor starts but the suspension either doesn't move or creepy up 1/2 in, with exception of a few days ago (that I wrote about above) where it inflated to the correct height and I drove it around for half an hour no problem. It even stayed inflated for almost 48hrs untill I drove the car the following day and within 1/2 mile the rear ns suspension was deflates again. All this time btw the rear off-side air suspension is at perfect heights.
