Arrggh! Suspension now at full extension!

[ChrisHGTV]

Hello all

Well the good news is my S212 rear suspension doesn’t seem to leaking anymore (after new air bags, new compressor, new air lines and new valve block)

But the other day the offside suddenly pumped itself up to full extension and the malfunction message appeared. I immediately thought aha must be broken sensor arm, so duly ordered a pair. I then had a look and the arms on both sides are intact, the offside must have been replaced already as it has the newer metal arm. During the process of jacking both sides the car seemed to level itself out and then drove ok for a day, so I thought maybe just a glitch.

Then today it did the same pumping right up With the malfunction message.

I assume this is pointing to a failed sensor on the offside? I’ll check the connections tomorrow but anywhere else worth investigating? Just as I thought it was fixed!

cheers!

 

[E55BOF]

If you're getting a malfunction message, the system detects that something is wrong, so I would suspect it's not the level sensor.

 

[ChrisHGTV]

Hmm ok thanks. I tried testing the sensors both sides with the car on stands and the arms disconnected - moving the sensor arms manually I could get some kind of response so it does seem they are sending a signal. After lowering the car it seemed to level up ok on a short drive. Then on a second test drive the malfunction message returned and the offside pumped itself right up again. I’m going the check for any obvious damage to the wiring, otherwise it‘ll be back to the garage! I’m assuming if there is no signal from a level sensor (whether a failed sensor or broken wire) the default position of the car would be fully raised?

 

[Robin220]

Hmm ok thanks. I tried testing the sensors both sides with the car on stands and the arms disconnected - moving the sensor arms manually I could get some kind of response so it does seem they are sending a signal. After lowering the car it seemed to level up ok on a short drive. Then on a second test drive the malfunction message returned and the offside pumped itself right up again. I’m going the check for any obvious damage to the wiring, otherwise it‘ll be back to the garage! I’m assuming if there is no signal from a level sensor (whether a failed sensor or broken wire) the default position of the car would be fully raised?

Hi Chris. I'm a new member and a pretty new merc owner. I think I'm struggling with the same issue with my rear suspension and wondered if you managed to get yours sorted? All started a number of months ago when the rear suspension collapsed completely. Found that the plastic push rod on the o/side had snapped. Replaced it and all seemed ok. I don't feel it has ever been right since. On virtually every journey I make, at some point I get the malfunction warning, and the o/side pumps up to its full extension. All of this while the car is travelling! Its been in to a decent MB garage more than once about this but nothing shows up on their diagnostics. Last time they had it for a whole week and ran the car every day. Not once did they have any issue. Of course, the day I collect the car and drive it home it decides to pump the one side up again!! Any Ideas?? Just about ready to set it on fire..

 

[ChrisHGTV]

Hi Robin - well touch wood mine is all sorted now and doesn't move at all even left for weeks at a time. So i had basically everything replaced (apart from the ride height sensors) and as you saw mine would still pump up one side to full height. So i took it to a different MB Indy who i had used before and they were actually now closer to me since i'm working from home. I thought it was a dead sensor. But they discovered that the previous garage (still a respected MB Indy) had connected the air lines the wrong way round into the valve block at the back, so the signal from the ride height sensor wasn't matched to the correct side (i assume that's what was happening). I had bought a valve block from Meissner - so a non-MB part. They are identical however the non-MB part doesn't carry the colour coding - hence the garage had attached the right to left and left to right. This was causing one side to pump to full height. The new garage correctly installed the lines and all fine since. From what i can gather if the car pumps up to full height it's due to an issue with the signal from the height sensor. So if the signal is intermittent maybe due to a failing sensor, poor connection - maybe you hit a bump and it disrupts the signal?, or broken ride height arm. In my case there was a mis-match between the signal and the response as the L and R had been switched. Could it be that the garage did the same and switched the air lines over without realising? Otherwise i would say most likely an issue with one of the sensors (the side that pumps to full height).

 

[Robin220]

Hi Robin - well touch wood mine is all sorted now and doesn't move at all even left for weeks at a time. So i had basically everything replaced (apart from the ride height sensors) and as you saw mine would still pump up one side to full height. So i took it to a different MB Indy who i had used before and they were actually now closer to me since i'm working from home. I thought it was a dead sensor. But they discovered that the previous garage (still a respected MB Indy) had connected the air lines the wrong way round into the valve block at the back, so the signal from the ride height sensor wasn't matched to the correct side (i assume that's what was happening). I had bought a valve block from Meissner - so a non-MB part. They are identical however the non-MB part doesn't carry the colour coding - hence the garage had attached the right to left and left to right. This was causing one side to pump to full height. The new garage correctly installed the lines and all fine since. From what i can gather if the car pumps up to full height it's due to an issue with the signal from the height sensor. So if the signal is intermittent maybe due to a failing sensor, poor connection - maybe you hit a bump and it disrupts the signal?, or broken ride height arm. In my case there was a mis-match between the signal and the response as the L and R had been switched. Could it be that the garage did the same and switched the air lines over without realising? Otherwise i would say most likely an issue with one of the sensors (the side that pumps to full height).

Brilliant, thanks for that. Plenty to go at there. Fingers crossed for an easy fix.

 

[ChrisHGTV]

Brilliant, thanks for that. Plenty to go at there. Fingers crossed for an easy fix.

Good luck! I do find that the joy of seeing the car sat at the correct height each morning is worth the effort and frustration!