Mercedes air suspension issue

[Scuzi]

Hello folks,

Car is a 2010 W251 Mercedes R350L CDI.

For the past few months, I would regularly come out to my car with the rear suspension on both sides collapsed the morning after driving it. This would happen daily for a period. Then for no obvious reason it would just stop and be completely fine.

Ever since earlier this week, the right side only would collapse and it does so relatively quickly, about 20 minutes after stopping.

I had it checked at the local Merc specialist during a service when lockdown started and they told me that the compressor is working fine so just see how it goes. They were just closing down and furloughing everyone at the time so I think they just wanted me out the door.

What do you think it is? I’d have thought an air leak would have consistent symptoms rather than intermittent.

 

[MatteH Oxford]

Get it running and spray some car shampoo over the lines, connections and shocks etc, you'll soon find the bubbles if there's a leak. If you are getting different sides randomly collapse, that would suggest a valve block issue.

 

[Nasher]

Pretty common with air suspension. They start leaking after a while.

 

[[TW]Fox]

Pretty common with air suspension. They start leaking after a while.

Well that's really helpful, thanks - I bet he hadn't realised it was leaking.

With ABC it's generally the struts or the compressor if you've not had a warning on the dash.

 

[-Ad-]

Don't forget there's a valve block as well where all the pipes feed back to. This is also known to be a leak/failure point. Have a good browse online regarding valve block leaks and how to access them.

It could be the struts/bags, but for it to happen just on the right side with both front/rear failing would be unlikely.

I'd be looking at the valve block.

Have a browse there's some decent guides and pdfs out there for Air suspension systems and how troubleshoot them. Try and get the suspension back up on a quiet day and listen in with your MK1 ear with the wheel off, that's a start at least.

 

[gailjon]

Father in law's E class estate with air suspension has had multiple issues with the suspension air lines corroding and leaking. (Owned from new, 2014)

The car would sink overnight then take and age to lift back up for the day then sink again with no use.

It has had the lines replaced twice so far and has been booked in again for another set to be replaced. All of thi is under the two year warranty you get with replacement parts as he had to pay for the first set of lines when it failed just months outside the original 3 year warranty.

I would suggest that the lines are the first port of call for you to look at replacing.

 

[geekman]

Get it running and spray some car shampoo over the lines, connections and shocks etc, you'll soon find the bubbles if there's a leak. If you are getting different sides randomly collapse, that would suggest a valve block issue.

This is by far the best way of diagnosing air suspension issues at home, and it's generally not too difficult either. You definitely want to get it fixed ASAP as a leak will overwork the compressor, which will lead to premature failure.

 

[MatteH Oxford]

Not knowing the system past about 1997, I'd check the electrical connections on the valve block too. It used to be just the one multiplug connector but my intimate knowledge is confined to pre 1997 cars I don't think the system has changed that much apart from the cars with the dynamic chassis control?

 

[Scuzi]

Thanks for the replies. I was out in the car today and when I started it, the suspension rose as expected but it remained uneven, with the near side a good 10-15cm higher than the off side. I previously had the “level sensing rods” replaced about 3 years ago. I wonder if they are playing a part?

I’ll look into the valve block as it seems the most likely.

As much as I love this car, it has a terrible habit of throwing up issues like this for a few weeks which then disappear never to be seen again.

 

[MatteH Oxford]

Thanks for the replies. I was out in the car today and when I started it, the suspension rose as expected but it remained uneven, with the near side a good 10-15cm higher than the off side. I previously had the “level sensing rods” replaced about 3 years ago. I wonder if they are playing a part?

The level sensors shouldn't affect the suspension when the vehicle is stationary and not running i.e. if you park up with everything fine and then later return to sagging, that suggests a leak.

 

[rpmmatt]

Had a similar issue with my 2005 E-Class, but mine was only air at the rear. As said will be either the bags, lines or valves. Use the soapy water trick to try and find the leak yourself, but be careful, don't do what I did and end up burning out the compressor by running the car to much without fixing the leak. My leak was very slow, like over a few days to drop a couple of inches, but it was enough to gradually wear out the compressor until I was driving along one day and lost all the air, bottom of the car was nearly touching the road.

From what I remember, the airlines/valves were pretty cheap fix, but the airbags were £800 a pair and had to replaced as a pair. Ended up replacing the airbags with a coil spring conversion kit from I think, Arnott. Was half the price of new airbags and no need to fix the compressor. Not sure if similar kits are available for an R-class? I didn't notice any difference over the airbags, unless very heavily loaded as obviously there was no self leveling.

 

[Scuzi]

Problem diagnosed. I busted out the soapy water.

Nearside rear air spring:


Offside rear air spring:

Pair of new springs fitted is £550 at the local specialist. I can buy pattern parts for £80 a corner but I don’t have the tools or the will to do it myself.

 

[-Ad-]

Wow, 2 gone at the same time, that's unfortunate.

Hopefully they cure the ills and then the sofa like air sus will be right as rain.

 

[DXP55]

Good find- A lad I worked for had a bill for £8k but fortunately he had took out 12 months insurance on it.

 

[Jez]

Dont drive it too much more like that Scuzi, it is mentioned above but you'll overrun the compressor and end up replacing that too. It sounds as though it has been leaking for a while.

 

[Scuzi]

Wow, 2 gone at the same time, that's unfortunate.

Hopefully they cure the ills and then the sofa like air sus will be right as rain.

It’s only the right side that’s gone but the garage said they have to be replaced in pairs. It seems these commonly go at about 100k miles so it’s only a matter of time before the other one goes. Might as well pre-empt it.

Dont drive it too much more like that Scuzi, it is mentioned above but you'll overrun the compressor and end up replacing that too. It sounds as though it has been leaking for a while.

Yeah, the compressor is runnning a lot and I don’t want to burn it out. I’m debating whether or not to drive to the garage (30min ~12 miles) or to call the RAC and have them flatbed it there.

 

[Jez]

If you have the cover, why not get them to flatbed it. I wouldn't pay though, if you will incur cost then 30mins more is probably not going to do much harm.

 

[Sirrel Squirrel]

I had both mine go on my 2005 E Class at 150k miles, they had to change the compressor too.

If I remember rightly it cost about £700 total.

 

[jpaul]

Do the vehicles not alert you if the compressor is running more than expected ? ie. just when the user requests a ride-level/firmness change
compared to parking ovenight, any leak losses during driving, whilst working the suspension, must be large in comparison

 

[Jez]

Nope, the first signs are that the car might come up with a red "STOP - CAR TOO LOW" message when the leak (or compressor) gets bad. Most will sink when parked quite early on as the pressure keeps them up, so you'd usually spot this early.