Problem with 2016 C350e Airmatic Suspension

[Basdeosing Persand]

Hi Martin, I got a mercedes c350e too, year 2016 and i got problem with my airmatic suspension last week. while driving i got the display "stop vehicle too low" , i stopped my car and i was able to raise the vehicle. But the next day i found my vehicle sitting down completely. The vehicle did not rise at all when i pressed the raise button, I could hear the compressor working so i try to look for air leak. I checked the pressure from the compressor and i found it too low as i was able to stop it with my finger. Tested it with a gauge and found the pressure to be 1.5 bar. I removed the compressor and found the discharge solenoid faulty as it was not clicking when i applied a 12 V dc current. the problem was that the valve in the plunger of the solenoid was stuck. with the help of a pin I pushed the ball ( seem like one as it is very small) in the valve and could then feel it having a springing motion. i tested it again with a 12 DC volt and could hear it clicking. tested the pressure again and could it it rising fast to 10 bar. Fitted the compressor and vehicle restored back into service. See if this might help you

 

[Martin Hedges]

Thanks for the info. The fact that mine is intermittent makes it more difficult to diagnose. All the sensor connections have been clears and resealed and at the moment it seems to be OK. The compressor seems to have decent pressure, but of course havent been able to check it when the issue is there, but will bear this in mind if it happens again. How did you remove the compressor? Did it need to go on a ramp for that?

 

[Basdeosing Persand]

If you have access to a ramp its better, I had to jack it up and put the safety stand before i went underneath the car to remove the compressor.

 

[Martin Hedges]

If you have access to a ramp its better, I had to jack it up and put the safety stand before i went underneath the car to remove the compressor.

COuld you by any chance let me have a couple of photos show how the suspension sits over the wheels. I think mine looks high but of course I have never really taken much notice of it before and dont have a comparison. ALternatively, let e have some measurements - say from the top of the rim of the wheel (rather than the tyre) to the top of the wheel arch so I can compare?

Thanks

 

[Martin Hedges]

Well a further update. HAs been fine for a couple of days and then tonight going to pick my son up I had the red "Stop - suspension too low" warning on the dash, I pulled over and check and the back looked fine, and then I noticed the front was down!!!!!! first time that has happened. Switch the ignition back on and got the vehicle rising message and after about 30 secs was back and OK.

I am wondering if it is the discharge solenoid which you mention which is sticking and then releasing. I am thinking car is saying drop XX (front or rear) suspension, discharge solenoid opens and then sticks open so suspension drops completely. Reservoir empties when it tries to fill with the valve open and then it closes and suspension refills. That would also be consistent with the taking too long to come back up error code.

Thoughts?

 

[Basdeosing Persand]

COuld you by any chance let me have a couple of photos show how the suspension sits over the wheels. I think mine looks high but of course I have never really taken much notice of it before and dont have a comparison. ALternatively, let e have some measurements - say from the top of the rim of the wheel (rather than the tyre) to the top of the wheel arch so I can compare?

Thanks

I've measured it and right now it is 14 cms.

 

[Martin Hedges]

Is that the same on all the wheels? From the highest point on the actual wheel itself, rather than the tyre, to the highest point on the bottom of the wheel arch (straight up from the wheel) ?

 

[malcolm E53 AMG]

I am wondering if it is the discharge solenoid which you mention which is sticking and then releasing. I am thinking car is saying drop XX (front or rear) suspension, discharge solenoid opens and then sticks open so suspension drops completely. Reservoir empties when it tries to fill with the valve open and then it closes and suspension refills. That would also be consistent with the taking too long to come back up error code.

Thoughts?

It’s quite possible there is an intermittent problem with the pump, either a design or batch problem - I’d certainly look into that it seems like the next logical step to take and should be relatively inexpensive.

 

[Martin Hedges]

The fact that it was the back first and then the front to me suggests that the issue is with some common part for both the front and back. Both the front or both the back have dropped quite suddenly and not come back on their own. I think this poretty much rules out a leak on one of the air bags as it would be consistent on that bag.

It therefore seems there is either a leak on a common supply line or one a valve. I am told by the mechanic that there are no valves on the bags themselves on this one. Basically has the individual bags, tubing from each feeding back to the compressor and valves and that is it. No reservoir apparently.

MY logic for the symptoms is this - the system is deciding the back (when the back dropped) or the front (when the front dropped) is too high and is instructing to let some air out of the two back or two front bags as appropriate by opening the discharge valve which I believe is a single discharge valve for all 4, with the valve block controlling which ones are connected and hence which ones lose air. However that discharge valve is not then closing when it should. It seems to be me this could be for one of two reasons - (a) the discharge valve is sticking intermittently allowing more air out that the system intends. This would then explain the error code that the compressor is taking too long to raise the car because if the valve is open then any air it puts in is lost out the valve.

(b) that the system controller is the issue and it is keeping the valve open when it should have closed it leading tot he same results as (a).

I assume that the solenoid valve would be normally closed, which would be the sensible way around. so that it needs power to open. Each time that the suspension has dropped it has been whilst the car is being used. The suspension has not come back up straight away. each time I have switched the car off and when I have switched back on I have the vehicle rising message and the suspension comes back up in about 30 secs at a guess, which I understand is about right. Switching the car off will kill the power to the controller and hence if the solenoid is being held open by the controller, the power holding it open will be cut and hence the solenoid will return to the normally closed position.

Is that more lilely than the solenoid being mechanically stuck and unsticking itself each time the car is switched off.

I had the codes read again this morning after the occurance last night and it was the same 3 codes - front left out of rangem, front right out of range and compressor taking too long to raise car (or something like that).

I am trying to logically link the fault codes to the symptoms but I cant explain the front sensors out of range errors unless both front sensors are faulty.

Any thoughts?

 

[Martin Hedges]

If you have access to a ramp its better, I had to jack it up and put the safety stand before i went underneath the car to remove the compressor.

Can you tell me where the compressor is located and how did you get it off (looking at pictures of them looks like it is a pipe and an electrical connector plus mounting screws).

Also, is the discharge solenoid changeable on it do yo think?

I am very much thinking my issue is that the discharge solenoid is being opened to drop the front or back a bit and then not closing when it should. The question is whether it is sticking or whether the controller is doing something strange and not closing it when it should (my reason for wondering whether it is the latter is because each time the issue has occurred (about 6 times now - twice the front and 4 times the back), when I have switch the ignition off and back one (which would kill power to the controller and hence the solenoid valve) the compressor has kicked in and raised the dropped end, indicating (a) that the car knows that one end has dropped, and (b) that the solenoid must have closed to allow the compressor to re-inflate the deflated air bags.

 

[Basdeosing Persand]

Can you tell me where the compressor is located and how did you get it off (looking at pictures of them looks like it is a pipe and an electrical connector plus mounting screws).

Also, is the discharge solenoid changeable on it do yo think?

I am very much thinking my issue is that the discharge solenoid is being opened to drop the front or back a bit and then not closing when it should. The question is whether it is sticking or whether the controller is doing something strange and not closing it when it should (my reason for wondering whether it is the latter is because each time the issue has occurred (about 6 times now - twice the front and 4 times the back), when I have switch the ignition off and back one (which would kill power to the controller and hence the solenoid valve) the compressor has kicked in and raised the dropped end, indicating (a) that the car knows that one end has dropped, and (b) that the solenoid must have closed to allow the compressor to re-inflate the deflated air bags.

The compressor is found on the front left side of the vehicle. To get access to it you have to remove the plastic covers underneath the vehicle. Yes the discharge solenoid can be changed. The control valve unit is found next to the compressor. May i suggest that you check the valve control unit and the wiring too.

 

[Martin Hedges]

The compressor is found on the front left side of the vehicle. To get access to it you have to remove the plastic covers underneath the vehicle. Yes the discharge solenoid can be changed. The control valve unit is found next to the compressor. May i suggest that you check the valve control unit and the wiring too.

Thanks. As I understand it there is the compressor and the valve manifold which to which the feeds to the various bags connect as well as the outlet from the compressor (there is no reservoir correct?) Is the discharge valve you are talking about on the compressor or on the manifold? And you dont need to remove the wheel to get to the compressor etc?

The other question is do you know where the control unit for the air suspension is located? I am wondering if this could be the issue as it would explain the intermittent nature of the fault if it has some damp in it or something. I want to check the part number as there are some I have found used but working for around £30 which at that money it would be worth trying if they are the right one

 

[Basdeosing Persand]

You right. I dont think there is any reservoir as there is one flexible pipe connected from compressor to the control valve unit and four pipes to the airbags, two for the front suspension and two for the rear one. The discharge valve is on the compressor. No need to remove the wheel but you have to remove the plastic covers. Here two links which can give you an idea where the units are located

 

[Martin Hedges]

Well got the compressor off and the discharge valve is definitely in a pretty poor state. I guess it is moisture coming out of the compressed air which has caused corrosion. Pump itself also showing signed of wear in similar way so ordered a new one and see how we go then

 

[Rudders]

Sorry to resurect this but did the new compressor solve the problem???
I have same year & model & very similar problem, to the effect that I can no longer use the car. The tyres all round are almost touching top insides of mudguards!
Compressor runs, says vehicle rising please wait, stops after just over a minute the Red warning stop vehicle too low.

 

[Martin Hedges]

Hi Mate,

Yes, the replacement compressor fixed mine, although I do seem to have a small intermittent leak on one bag now (If I dont use it for a couple of days the one corner will be noticeably lower but rises back up as soon as I use the card and then stays up so I havent dont anything else about that at the moment).

I would say the fact that it is down on all four corners, the vehicle knows it is down and tries to raise it but it doesnt raised definitely points to the compressor. Depending on how mechanically handy you are, you can take the compressor off and wire it directly to a 12V supply and see what the pressure output is like. If you can lift the car up (at least the front left corner) it is quite easy to get to. There are piston kits you can get as the common thing is the piston wears and doesnt give the required compression. Otherwise you can get a replacement compressor from ebay for about £300.

I would say what has likely happened is the suspension dropped due to the colder temperature (universal gas law, P*V/T = constant so if temperature drops and volume stays the same then pressure drops). Next time you went to start the car, sensors said suspension was low so fired up the compressor and opened the valve block to feed all 4 corners, but because the compressor was not working properly, the pressure from the bags back releaved through the compressor resulting in all 4 corner dropping into the stops. It is possible that you have a leak as well but I would definitely look to the compressor first and once the car is rising then see if it drops overnight on any corner. You may need to replace the relay for the compressor as well (new compressor will come with a new relay).

Let me know how you get on

 

[Janchee]

Just as an update to this thread, I have a 66 plate E class that’s just had a new pump fitted after it failed. Mercedes paid 50% and send them back to Germany for remanufacturing (known fault in these models)

 

[Rudders]

Thanks for that Martin, like yours it has had had some issues lowering whilst driving, stop & switch off, start back up & been okay for a day or 2. Cold could have been a contributive factor finishing it off as it started about 2 weeks ago when the snow was around!
Tried to get some info from Mercedes dealers but their not the most helpful to be honest, more interested in getting it on diagnoses for £200 ish. But the parts dept did say there is not a compressor in the country or Germany at the moment, if I pay the £411 + vat they will put me one on back order!

It looks like a fine day so I will look at raising the car somehow & get it off, incidently which fusebox is the relay in?

 

[Rudders]

UPDATE for those interested!
I struggled to get a new compressor from any MB dealer, all on back order. To cut a long story short I decided to buy a repair kit off ebay for £29.99, DONT DO IT!!!
Spent a lot of time, nearly impossible to split the top of the piston which holds the seal, although it tells you to be gentle you would never get it off. any way after some time consuming work & refititting guess what? It still wouldnt work.
After a couple of weeks MB dealer phoned and they are back in stock £395 + vat & £72 + vat back for partex, oh and £12 for new relay.
Purchased, spent only an hour rmoving old one (again) bolted up new one everything works with no issues.

Hope this helps anyone with similar problems.

 

[Adrian Lewis]

I have had exactly this problem on my C350e 66 plate this month, although the first experience was the red "Vehicle too low - Stop" message. All four corners were right down. Nothing would fix it so I called recovery service, but after about 30 minutes playing with the raise/lower switch, turning on and off etc, the car suddenly fixed itself so I cancelled the recovery and drove home. Then yesterday after driving off, no messages but I could feel the rear bouncing as if I had square wheels. Took a look and rear only had collapsed both sides. Took it my local indie garage who got the same fault codes as above ("front too low" - no it wasn't!), and then suddenly while the car was up on ramps, it fixed itself again.

I bought this car 2nd hand and it has an RAC extended warranty still active, but I believe that "intermittent" faults don't qualify. Is everyone so far happy that replacing compressor and relay fixes this for good? Any advice on how to approach the warranty?!