Rear AirMatic issue - 07' S550 4matic

Drove to work this morning, no issues. I drove home for lunch today and on my way down my driveway, the rear sounded and felt stiff. I got out and saw both sides of the rear were lowered, Im guessing all the way, top of the rear tires behind the wheel well. Low rider! lol. Front was fine. I hooked up Star and ran the pneumatic tests. The pump and front level control valves passed, the rears both failed for the level control valves. I ran all the other tests and they all passed, including pump and leak tests. I then noticed you can manually go into each strut and add or bleed air to them. To my surprise I was able to pump the rear up. I re ran the tests and the rear passed this time. I left it for 10 minutes and it seemed to hold. Then I drove up the driveway and back down, a 30 second drive at best. When I returned to the garage, the rear was almost back to the floor again. Do I need new struts? Is it both of them? Big job or can I DIY? I was quoted $1800-2000 for both from a nearby mechanic. Im a newbie to Mercedes vehicles.

I pumped the rear back up via DAS again and let the car sit. It has been sitting in the garage for over 18 hours now and the rear has stayed up and level. What the heck? Maybe the struts arent bad but something else linking the two is?

I appreciate all your feedback and help with this. I would love to tackle this myself.

Comments

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ChannelZer0 made a comment.
1 year ago

To my surprise I was able to pump the rear up. I re ran the tests and the rear passed this time. I left it for 10 minutes and it seemed to hold. Then I drove up the driveway and back down, a 30 second drive at best. When I returned to the garage, the rear was almost back to the floor again. Do I need new struts? Is it both of them? Big job or can I DIY? I was quoted $1800-2000 for both from a nearby mechanic. Im a newbie to Mercedes vehicles.

I appreciate all your feedback and help with this. I would love to tackle this myself.

 
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ChannelZer0 made a comment.
1 year ago

I pumped up the rear around 3pm yesterday. The car has sat in the garage since then and the rear has stayed up and level. What the heck?

 
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ChannelZer0 made a comment.
1 year ago

May not the struts but something common to both the rear struts only???

 
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MercedesMedic made a comment.
1 year ago

Check both rear tires. If they have dropped both the same amount my guess would be that you have an issue with the airmatic valve block. If one side is slightly higher than the other you may have a bad airbag on the side that has dropped the most. If one of the airbags leaks it will bring the whole rear of the car down regardless due to the weight of the car.

If you have STAR diagnostic run a few more test. You can test the valve block and also active (raise/lower) each one of the air struts. Let me know what you find out.

 
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MercedesMedic made a comment.
1 year ago

Hey I just saw the rest of your comments. You must have a bad air bag. What you are saying is that the car starts to drop when you drive. In which case it may indicate that the airbag only leaks air when it bends a cerain way. For example if the damage was near the top. There is a small part of me that thinks that the valve block can not be elemenniated yet. The car adjustes the ride all the time. It is doen via the valve block and the release valve in the air compressprossor.

If I was you I would drive the car until it drops. Then when the problem does happened hook up your star diagnostic and perform all the test. Check air compressor, valve block and both rear airbags.

I got to say that this is tricky and any Mercedes mechanic will have a hard time narrowing it down. You are luck to have star diagnostics and carry some of the testing yourself.

 
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ChannelZer0 made a comment.
1 year ago

Thank you very much for your feedback. Yea its really tricky. I will try what you suggested and report back.

Does a bad airbag mean a new strut assembly? Would I replace both or just one if its faulty?

 
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MercedesMedic made a comment.
1 year ago

Yes by airbag I am refering to the air springs in the rear strut assembly. You need to make sure that the problem is one of the rear strut assemblies and not the valve block that is at the front. If you find that one of the struts is leaking, you can simply replace the failed one. No need to replace both unless you want too.

 
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MercedesMedic made a comment.
1 year ago

If you need to change the rear suspenion struts it is not that difficult. Check out the video below. They run around $250 each.

OEM Part Number

Rear Left:

2213202113
2213205513
221 320 21 13
221 320 55 13
A2213202113
A2213205513
A221 320 21 13
A221 320 55 13
AS-2604

Rear Right:

2213202213
2213203613
2213205613
221 320 22 13
221 320 36 13
221 320 56 13
A2213202213
A2213203613
A2213205613
A221 320 22 13
A221 320 36 13
A221 320 56 13
AS-2603

 
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ChannelZer0 made a comment.
1 year ago

Ok here is what I found out.

I moved the car up and down the driveway again, checking the back wheels every 5-10 seconds. They were moving down. When I got back down the driveway, they were nearly all the way down again. I hooked up SDS and found no trouble codes in the airmatic system. I then ran all the pneumatic tests and the left and right failed. It said "Component 'Y36/6y3 and /6y4(left and right rear level control valves)' is not operating properly or the line between the valve block and the suspension strut is not leaktight." With the level valve open, it would only build up to about 4 bar on each rear valve. I noticed before it does this part in the test, it checks the level of the suspension strut and adjusts if necessary. When testing the rear control valves, it stops for a second on this check and moves onto the next one. When I test the front valves, it will take more time and attempt to adjust the level, before moving onto the next check. Just thought I would throw that out there.

I also ran the following tests and it passed them all. the AIRmatic pressure release valve, leakage test between valve block and central reservoir and leakage between the compressor and valve block. I tried grabbing the rear wheel wells and shaking the rear up and down. The driver's side seemed more stiff than the passengers side, which moved a little more. Im still baffled.

I noticed your PO box is in Parkville. I used to live there up(Double Rock Park neighborhood) until 2+ years ago and moved up bel air rd 30 minutes to Forest Hill. You mentioned the part I might need. Are there local sources?

Thanks again!!

 
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ChannelZer0 made a comment.
1 year ago

i can add that when i press the vehicle rising button on the dash nothing happens, no led light or visual notice on screen. i did check it with das and i was able to turn the led on and off via DAS.

 

Also, i ran additional tests. when i tested component B22/3(rear axle level sensor) it was suspect. Signal 1 of the component only reads 0.45V and the range is 2.00-3.00.  for comparison i checked the two front ones and they fell in the acceptable range. 

 
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ChannelZer0 made a comment.
1 year ago

Thanks again for your help.  Earlier this afternoon I was able to solve this.  I was puzzled about both rear struts going at the same time and the ability to pump up the rear and then pass the tests.  It went down once I started driving but I never heard a leak then or when conducting tests via DAS.  I took that bad reading on rear level sensor and ran with it.  Both rears giving out once driving and not when parked was starting to make sense.  A couple of clicks later I had the location of the sensor and I jacked the car up onto jackstands.  Once underneath the rear, I saw the sensor.  Wiring was intact.  Then I saw the pivot arm that is attached to the sensor on one side and to a ground parallel cross bar on other.  The latter end was no longer attached.  (See pics)  I was able to zip tie it in place for now but I need to order a new part.  Can I just order the clip that attached the pivot arm end to the cross bar?  or do I need to order something else?

Once in place, I ran the tests in DAS again and the rear sensor passed with the correct voltage range.  I rant he pneumatic tests and let all the corners level themselves.  Not sure if I need to do anything further with this or calibrate or something?  I took the car for a ride and it smooth and normal.  Woo hoo!

arm off 2

arm off

 
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ChannelZer0 made a comment.
1 year ago

This pic is of an intact rear sensor I got off the internet.  I put a curve around where it looks like mind broke off.  Can I just get a new arm? rear

 
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MercedesMedic made a comment.
1 year ago

Great job on figuring this out. You probably just saved yourself a few hundred dollars on troubleshooting alone. And you didn't replace the struts for no reason. :)

The easiest thing to do is order a new level sensor which will come with the clip that broke. Online they run around $50 for a used one. Part number should be this but check yours to be safe: 0105427717 / A0105427717 / A 010 542 77 17

I would also call the dealer because it may not be much more new. The other option is to weld or remake the clip that broke if you want to go that route.

 
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CarCarePros made a comment.
1 year ago

Excellent troulbshooting. Some places you may have spend a few thousands dollars on new rear struts you didn't need.

 

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