Hi everyone, after a 12 or so year break (my last Merc was a W126 420SEL!) I've recently acquired a 2001 '51 plate' S320CDI, just over 91k miles and only 2 owners before me. Needless to say, it came with a few little errors. Most were related to the PSE pump, a quick strip down, clean, fuse replacement and reassemble sorted those out (great YouTube tutorial by a French chap 'I Fix My Benz' or something is the channel name), but it has an odd suspension issue.
Visually, the problem is that the front of the car sits a little higher than the rear. I can comfortably fit 4 fingers in the front arch gap (I have quite big hands...!), where I have to angle 3 fingers to get them in the rear (scientific, I know - pic of the car attached, albeit not at the best angle to see what I'm on about)
Aside from a few bulb warnings which I will get round to replacing, the only error displayed on the dash is 'Display Defective ABC Visit Workshop!' (pic attached). This strikes me as being odd, as I have the airmatic suspension
Here's what I've done so far in my troubleshooting process:
Unhooked the battery (and put it on charge, I know they don't like low voltages!) and left the car for 12+ hours to see if the suspension dropped at all. No movement from the suspension, arch height from the floor in all 4 corners hadn't budged a mm.
Checked all of the wiring in and around the compressor and valve block - all perfect, no corrosion or broken wires.
To check the above, I jacked up the drivers side (RHD car) front wheel and in doing so, air was released out of the brass fitting around the air line at the top of the strut - is that normal? I removed the brass fitting where the air line goes in, (whilst the wheel was up in the air), replaced the o-ring for good measure and reassembled it. I did it again after the 'rebuild' and it was exactly the same. I jacked up the p/s front wheel at a later date and it didn't do it over there.
While it was up in the air, I took the rods off the level sensors and checked they weren't seized up. They moved fine, exactly as I would have expected them to.
With the air out of the shock, when the car is let back down, it collapses right down (as expected). I leave it on the jack so it doesn't fully compress and when I turn the ignition key on (engine running or not), the compressor kicks in, raises the front of the car up, I get a little 'psssssst' as (I assume) the pressure relief valve kicks in, the front drops slightly and it settles.
On that note, I removed the pressure relief valve as I wanted to test it - there was a very small pssst as I removed it, but not much air came out - is that normal? I had put some blocks down under the jacking point for the car to settle on to, but it didn't drop. I half expected it to let all of the air out when the valve was released? Anyway, it looked immaculately clean so I hooked it up to my 12v bench PSU and it pulled the little piston in (and subsequently launched it, along with the spring across my workbench when I removed the power... doh!), so that all looked fine.
None of the dash buttons relating to the suspension do anything.
Other things of note: It seems to have the 'later' style struts, with the full mastic/epoxy top. I'm guessing these either must be replacements or have had the repair kit - as according to the w220.ee website, cars out of the factory didn't have these until 2004? The compressor has also been replaced at some point as it's not an OE Mercedes unit.
So, my main questions are:
Why am I getting an ABC error message when I have airmatic suspension?
When I remove the pressure relief valve, should it have lost all air pressure, or is there a failsafe in there somehow?
Anyone got any ideas what else I should test, before I look for someone with a Star diag machine (ideally someone mobile and local to me on the Derby/Notts border as the car has no MOT currently!)
Apologies for the long, rambling post after a lengthy absence from the forum!
Cheers, Martin
P.S. Yes, I agree, the wheels look awful in black and will be getting repainted soon!
Visually, the problem is that the front of the car sits a little higher than the rear. I can comfortably fit 4 fingers in the front arch gap (I have quite big hands...!), where I have to angle 3 fingers to get them in the rear (scientific, I know - pic of the car attached, albeit not at the best angle to see what I'm on about)
Aside from a few bulb warnings which I will get round to replacing, the only error displayed on the dash is 'Display Defective ABC Visit Workshop!' (pic attached). This strikes me as being odd, as I have the airmatic suspension
Here's what I've done so far in my troubleshooting process:
Unhooked the battery (and put it on charge, I know they don't like low voltages!) and left the car for 12+ hours to see if the suspension dropped at all. No movement from the suspension, arch height from the floor in all 4 corners hadn't budged a mm.
Checked all of the wiring in and around the compressor and valve block - all perfect, no corrosion or broken wires.
To check the above, I jacked up the drivers side (RHD car) front wheel and in doing so, air was released out of the brass fitting around the air line at the top of the strut - is that normal? I removed the brass fitting where the air line goes in, (whilst the wheel was up in the air), replaced the o-ring for good measure and reassembled it. I did it again after the 'rebuild' and it was exactly the same. I jacked up the p/s front wheel at a later date and it didn't do it over there.
While it was up in the air, I took the rods off the level sensors and checked they weren't seized up. They moved fine, exactly as I would have expected them to.
With the air out of the shock, when the car is let back down, it collapses right down (as expected). I leave it on the jack so it doesn't fully compress and when I turn the ignition key on (engine running or not), the compressor kicks in, raises the front of the car up, I get a little 'psssssst' as (I assume) the pressure relief valve kicks in, the front drops slightly and it settles.
On that note, I removed the pressure relief valve as I wanted to test it - there was a very small pssst as I removed it, but not much air came out - is that normal? I had put some blocks down under the jacking point for the car to settle on to, but it didn't drop. I half expected it to let all of the air out when the valve was released? Anyway, it looked immaculately clean so I hooked it up to my 12v bench PSU and it pulled the little piston in (and subsequently launched it, along with the spring across my workbench when I removed the power... doh!), so that all looked fine.
None of the dash buttons relating to the suspension do anything.
Other things of note: It seems to have the 'later' style struts, with the full mastic/epoxy top. I'm guessing these either must be replacements or have had the repair kit - as according to the w220.ee website, cars out of the factory didn't have these until 2004? The compressor has also been replaced at some point as it's not an OE Mercedes unit.
So, my main questions are:
Why am I getting an ABC error message when I have airmatic suspension?
When I remove the pressure relief valve, should it have lost all air pressure, or is there a failsafe in there somehow?
Anyone got any ideas what else I should test, before I look for someone with a Star diag machine (ideally someone mobile and local to me on the Derby/Notts border as the car has no MOT currently!)
Apologies for the long, rambling post after a lengthy absence from the forum!
Cheers, Martin
P.S. Yes, I agree, the wheels look awful in black and will be getting repainted soon!
