Airmatic suspension problem on w205 C class C350e estate (2016)

themadsinger

New Member
Joined
Oct 27, 2020
Messages
5
Location
Kettering
Car
2016 Mercedes C350e
Wonder if anyone can provide some suggestions for the cause of my suspension problem

I have a C350e which is 4 1/2 years old. DOne just over 60K miles

2 weeks ago when driving the children home from school the back end suddenly became very bouncy. No warning message on the dash board. I pulled over and checked and the suspension was right down on both back wheels. Looked fine on the front. I got back in the car and switch the ignition back on and it came up vehicle rising on dash display. Suspension came back up to normal level and drove home fine. I went out it in later in the evening and was all fine.

Next morning, on the way to school, got a dash message stayin STOP VEHICLE - VEHICLE TOO LOW. Before I had a chance to pull over that disappeared and when I did pull over (maybe a minute later) The rear and front suspension looked fine. Even when the message was on the car drove fine leading me to think that it was a false warning but I dont know for sure.

On the way home from school that evening, it did the same thing it did the evening before - back became very bouncy, no warning message but rear suspension low (wheel arch over the tyres). Again came back up when I stopped and started and pressed the suspension up button. I could hear the compressor kick in so that seems to be working.

The car was not used from Thursday to Tuesday due to the issue, during which time the suspension stayed up where it should, so it seemed the issue isnt a leak on any of the air springs. Similarly, when I switch the car on on Tuesday to take to get fault codes read, I didnt hear the compressor kick in.

On the way to the garage (less than 5 mins from home) the dash warning message to stop again came on and this time the rear suspension definitely dropped right down. Again, though, when I pulled in and pressed the raise suspension button, it came back up and was fine for the remainder of the 8 mile drive to the garage.

The code reading didnt give any errors for the rear which is what has been dropping. Apparentlly there were codes for out of range for both front sensors and also an error for the compressor taking too long to raise the height.

Based on the symptoms, and that the compressor seems to be working and raising the car, and that it is an intermittent issue, my conclusion (before error codes read) was that it was either a sensor issue - system thinking rear is too high and dropping the rear, but doesnt pick up the change and therefore keeps trying to drop it. However, the fact that the error codes dont indicate a problem with the rear suggests that is not right. The other possibility was that it was a discharge valve sticking open - the system was maybe opening a valve to lower the suspension and that was sticking, leading to the read dropping completely. That would then lead to the compressor taking to long fault as it would be trying to bring up but the air put in goes straight out. However, the fact that the car was not warning when the system was too low the first 2 times it happened would suggest otherwise, unless, of course, it is both.

The technical info which the guy at the garage has managed to get apparently points to the compressor leaking somewhere but I cant quite get that unless, I guess, there is a valve sticking open which is allowing air to feed back from the rear springs and causing them to drop.

After it was looked at it was OK for a day and then it gave the stop warning again but this time it was the front which had dropped not the back. Got the codes read again next morning and the same three as before were there (cleared them before). It happened afew more times since then to both the front and the back separately both never at the same time. Each time when the car is switched off and back on I get the car rising message and it comes back up within the time frame you would expect bearing in mind that it is completely filling two bags 30 secs or so.

The fact that it is switching from front to back leads me to conclude that it cant be a leaking air bag or supply line, and there is no reservoir - the compressor connects direct to the valve manifold. The only common outlet for the air bags is therefore the discharge valve and I am therefore concluding that this must be staying open beyond where it should, either because it is stciking or because the controller is holding it open longer than it should, The compressor is then taking too long to refill due to that valve being open. What I cant reconcile with that is fault codes on the two front sensors.

I am thinking this is one of those issues that if someone has seen the combination of symptoms before they might be able to help.

If anyone has any thoughts with logic to link it with the symptoms I would be very grateful. If you agree with what I say which would you lean towards - the valve or the controller (apparently although the valve is a separate part connected to the compressor it isnt available as a separate part so would need to replace the whole compressor even though that seems to work OK.

I have also read somewhere that there can be a leak inside the valve manifold but cant see that is the issue here and the car does not drop when left standing but again if anyone thinks this could be the issue please let me know how that would cause this.

Thanks
 

Farmer boy

Active Member
SUPPORTER
Joined
Sep 7, 2015
Messages
278
Location
North East England
Car
S205 250 AMG Line
I had to have my 2016 50k miles S205 recovered to dealers earlier this year as car went down on all 4 corners and was not drivable. Mobile recovery (RAC) did a code reading showing compressor cut out after running longer than system allows. Car went off on flatbed to dealer. Call later that day car fixed was compressor at fault so new compressor and it’s relay fitted. Even though car was a year out of warranty MB chipped in with 50% of the cost so just over £300 to pay. Picked car up and drove home keeping to the 50mph speed limit. 20 miles into journey yellow warning vehicle low and ride went hard, slowed down to 30 mph and continued. Three miles later and only 1/2 mile from home the dreaded red stop car warning came on. Called dealer who arranged for another rescue. I discussed possible fault suspecting the valve unit as the car had a new compressor and that all 4 corners failed so unlikely to be the air bags. Dealer said the new valves rarely fail ( EBay has plenty of replacement parts for sale so there must be a market for them).

The following day car was ready for collection so went and collected it. Discussed fault which was apparently a faulty replacement compressor so a new one and it’s relay fitted. I asked if the valve block had been changed and was again told no need as the new design is reliable. I said it was a good job they had two compressors in stock the service manager said we have done a number of them. As MB parts have a warranty no charge for the replacement part or labour. Drove home expecting to have problems again but all well and no problems in the last 5 months despite the car sometimes not moving for over a couple of weeks.

So what did I learn? W205 airmatic compressors fail at low miles, QC on replacement parts suspect, overheating or stuck compressor may blow a high amp fuse and relay, the valve block is separate from the compressor.

What could cause the front end to go down some times and the rear at other times? Faulty valve block? Faulty airmatic electronics box? Sticking compressor relay, sticking pressure relief valve, damaged/ corroded wire from level sensor(s)? Without fault codes swapping out parts could prove very costly. The relay will be about £40, valve block £70, electronics box £300? Then labour on top. Sorry to ramble on I hope you get sorted.
 
OP
OP
T

themadsinger

New Member
Joined
Oct 27, 2020
Messages
5
Location
Kettering
Car
2016 Mercedes C350e
I had to have my 2016 50k miles S205 recovered to dealers earlier this year as car went down on all 4 corners and was not drivable. Mobile recovery (RAC) did a code reading showing compressor cut out after running longer than system allows. Car went off on flatbed to dealer. Call later that day car fixed was compressor at fault so new compressor and it’s relay fitted. Even though car was a year out of warranty MB chipped in with 50% of the cost so just over £300 to pay. Picked car up and drove home keeping to the 50mph speed limit. 20 miles into journey yellow warning vehicle low and ride went hard, slowed down to 30 mph and continued. Three miles later and only 1/2 mile from home the dreaded red stop car warning came on. Called dealer who arranged for another rescue. I discussed possible fault suspecting the valve unit as the car had a new compressor and that all 4 corners failed so unlikely to be the air bags. Dealer said the new valves rarely fail ( EBay has plenty of replacement parts for sale so there must be a market for them).

The following day car was ready for collection so went and collected it. Discussed fault which was apparently a faulty replacement compressor so a new one and it’s relay fitted. I asked if the valve block had been changed and was again told no need as the new design is reliable. I said it was a good job they had two compressors in stock the service manager said we have done a number of them. As MB parts have a warranty no charge for the replacement part or labour. Drove home expecting to have problems again but all well and no problems in the last 5 months despite the car sometimes not moving for over a couple of weeks.

So what did I learn? W205 airmatic compressors fail at low miles, QC on replacement parts suspect, overheating or stuck compressor may blow a high amp fuse and relay, the valve block is separate from the compressor.

What could cause the front end to go down some times and the rear at other times? Faulty valve block? Faulty airmatic electronics box? Sticking compressor relay, sticking pressure relief valve, damaged/ corroded wire from level sensor(s)? Without fault codes swapping out parts could prove very costly. The relay will be about £40, valve block £70, electronics box £300? Then labour on top. Sorry to ramble on I hope you get sorted.
Thanks. All the parts are pretty accessible to should take too much time to do. The fault codes are not very helpful to diagnosing the issue. I know if I take it to Mercedes their "technicians" (aka fitters) will just throw parts at it at my expense and not actually get to what the issue is but "fix it" by replacing everything with a ridiculous labour charge on top of a premium price for the part so I am not rushing to take it to them.
 

Users who are viewing this thread

Top Bottom