2004 Mercedes E320 CDI Rear Air Suspension Issue

[Mar64]

Hi, I've got a 2004 Mercedes E320 CDI estate and have an intermittent rear air suspension problem.

The rear air suspension on both sides will drop at the same time. Always with the car parked and usually happens overnight, although the suspension will occassionally stay up for up to 3 days!!! I mistakenly took it to a Mercedes specialist who assured me it was the valve body and compressor. So I had these replaced and it's still exactly the same.

However I've noticed that if I disconnect the battery then the car does not go down at all, which suggests that it's an electrical issue.

So if it's an electrical issue where would be the obvious places to start looking in order to try and resolve this issue?

Thanks,
Mark

 

[alexanderfoti]

Most of the time its the rear air bags leaking, or the tanks inside the rear subframe.

Easy to check the valve body, spray the lot with leak detection fluid and see if its leaking! Should be very much clear cut. Compressors don't cause leaks though.....

 

[Mar64]

Thanks for the reply.

The car is not going down when the battery is disconnected. So I assume from that, that it's not a leak but some electrical issue on the car.

 

[alexanderfoti]

Does it do this every time, in different locations? Bags often don't leak if parked in a certain way etc......

if 100% then its likely that the car is waking up periodically and trying to level itself. If it has keyless, could be the handles waking it up, if not then 100 other things potentially.

 

[sidmon]

Hi, I've got a 2004 Mercedes E320 CDI estate and have an intermittent rear air suspension problem.

The rear air suspension on both sides will drop at the same time. Always with the car parked and usually happens overnight, although the suspension will occassionally stay up for up to 3 days!!! I mistakenly took it to a Mercedes specialist who assured me it was the valve body and compressor. So I had these replaced and it's still exactly the same.

However I've noticed that if I disconnect the battery then the car does not go down at all, which suggests that it's an electrical issue.

So if it's an electrical issue where would be the obvious places to start looking in order to try and resolve this issue?

Thanks,
Mark

Is this the vehicle that had a welding incident prior to the issues?

 

[sheryllee]

http://www.mercedesmedic.com/mercedes-lowers-drops-parked-air-suspension-self-leveling-problems/
Read it might help you

 

[Oldspanners]

I replaced airbags on a friends E320 which had a leak around the electrical connector to the valve on the air bag. This may be your problem in that disconnecting the battery stops the leak there.
Buy some gas leak detector much stickier than soapy water and spray it around the electrical connector and of course the air line on the air bag.

 

[Mar64]

UPDATE; So after 5 days with the battery disconnected the suspension still dropped at the rear!!! I drove it yesterday and when I parked it up - with battery connected - the rear dropped over the space of an hour. Again it dropped both sides at the rear, at the same time.

alexanderfoti; I have had the valve body replaced, so this shouild not be leaking. I will check it again though. Also if this was a leaking air bag issue then it would drop one side and then the other, as I would have thought it unlikely they would have the same sized leak. I have another Mercedes with a clear air bag issue and it drops only on one-side

sidmon; No welding has been done to this car from what I can see.

sheryllee; Thanks, the link was informative. I will check the rear level sensors.

Oldspanners; I've already checked around the bags previously and couldn't see any leaks. Although that is no guarantee that there isn't a leak. However when I've got the rear up I will have a look around the connectors.

Also just out of interest. The Rear Air bags that are advertised on Ebay, the ones around £100 from China. Are these any good? Has anybody any experience of trying these?

 

[sidmon]

If it's the car I'm talking about the issue was caused after an exhaust bracket was welded with the battery still on the car causing these issues. If you purchased the car within the last few months it sounds likely to be the same vehicle. That would rule out the airbag's being at fault and would point to an electric issue possibly an airmatic module/ECU issue?

 

[alexanderfoti]

UPDATE; So after 5 days with the battery disconnected the suspension still dropped at the rear!!! I drove it yesterday and when I parked it up - with battery connected - the rear dropped over the space of an hour. Again it dropped both sides at the rear, at the same time.

alexanderfoti; I have had the valve body replaced, so this shouild not be leaking. I will check it again though. Also if this was a leaking air bag issue then it would drop one side and then the other, as I would have thought it unlikely they would have the same sized leak. I have another Mercedes with a clear air bag issue and it drops only on one-side

The way the bags are plumbed, they can leak across the rear axle in one go, or both bags can have a leak!

 

[V6Matty]

I seem to remember they were occasionally known to chafe near the T join around the rear axle, as Alex though get yourself around everything with some leak detector to find where it’s hiding

 

[malcolm E53 AMG]

If they are the original airbags like everything they wear out I’ve seen plenty of 212s with ‘sagging posteriors’ with this problem in fact one parked up yesterday. The rear bags generally fail gradually and intermittently a lot of owners being perplexed as to why the car doesn’t drop when the car is stood only to drop the next time the car is used which is probably due to the variation in ground level when the car is parked up

 

[Mar64]

Thanks for the replays guys.

So I've inspected and sprayed soapy water underneath the vehicle at any airmatic connections and also around the rear Airbags and connections. All appears to be air tight.

I've also taken a look at the rear level sensor and connecting rod. It appear to be undamaged. However I assume that these can't be moved by hand. The reason I ask is that I wasn't sure if it was seized, as the rod and arm was stiff, which I assume is how it's meant to be?

I also briefly took a look at the compressor, however this is brand new as it was replaced not long ago, so I assume it's ok. I did notice that the air filter had not been attached to the compressor pipe when it had been fitted, but I connected this and the car still dropped to the rear overnight. Out of interest does anyone know where on the compressor is the valvebody. It's doesn't appear very obvious?

Also just out of interest. The rear Airbags that are advertised on Ebay, the ones around £100 from China. Are these any good? Has anybody any experience of trying these?

 

[malcolm E53 AMG]

Members on here have generally used Aerosus for replacement bags with success

https://aerosus.co.uk/mercedes.html

 

[pgh13]

Arnott also have a good rep. They have how to do it videos on YouTube too. I'd be wary of Chinese ones.

 

[Mar64]

UPDATE; It was indeed both rear airbags that were at fault. I used Arnott and replaced both. I inspected them afterwards and couldn't see any problem, however all I can assume is that over a long period of time they perish and fail to hold air.

Anyway thanks for all your help.

 

[Blobcat]

Good hit rate on the forum at the moment

 

[00slk]

UPDATE; It was indeed both rear airbags that were at fault. I used Arnott and replaced both. I inspected them afterwards and couldn't see any problem, however all I can assume is that over a long period of time they perish and fail to hold air.

Anyway thanks for all your help.

Have a close inspection of the old airbag and pull the airbag up, you will find where the rubbing has taken place. I too had the same issue and when I replaced the rear airbags couldn't see any damage to the old bags. You'll find a small part that has a very slight rubbing. That's where it is leaking under high pressure The car only has to be parked on very slight uneven ground and the damaged rubber seals itself against the top part of the airbag which stops the bag leaking which also makes it an intermittent fault.

 

[00slk]

Good hit rate on the forum at the moment

That's because we are very popular