Problem:
Left Rear Air Spring (Bag) SLOWLY looses air pressure when engine OFF. (Intermittently)

Car: 07 W251 R320 (4 corner Airmatic)

Diagnosis:
- No Air leaks at rear bag/or line. (Soap and Smoke test)
- Engine OFF - WAKING UP Airmatic Control Module (when opening a door) re-pressurizes and levels the low Left Rear Air Spring.
- W251 is Level when engine is running and pump does not constantly run with engine ON
- No CF Error codes
- Airmatic Suspension Links not broken or bent (but rusty)
- Cold or Warm conditions don't seem to make any change

Possibilities:
- Bad wheel level Sensor - but no errors and levels properly with power
- Bad Airmatic Control Module - but no errors and levels properly with power and "wake up condition"
- Replace Links - but they are not seized/bent/broken
- Replace Airmatic Control Valve - I hear the valve always blowing off sometimes even while driving (seems normal)

Question:
- If I replace the links do I need to use STAR to re-level?
- Is there a way to diagnose a bad Control Valve
- Is my diagnosis incorrect?

Appreciate your experience.

 

I do not have the Airmatic System (rear only) but the right rear sags now and then recently. My system does not level after opening the door (first thing in the morning) but I don't know if it should. My R does level after starting.

For you I think it may be the bag slowly leaking since the system seams to be able to correct itself and level. I see you did a leak test but this may not find the leak (bag on vehicle). I've read as I'm sure you have, that the leak may be under the bag or just not in a spot you will find it. Some guys have taken the bag off and did a complete submersion test (and sometimes not finding a leak).

It will be interesting to see what more experienced member offer.

 

You know R350-2007,
You bring up a great point, that perhaps the bag on the car may have the leak under a fold?

I'll try that!
and get back
Thank YOU

 

hi all,
i recently had "visit workshop" on my 2006 R500, and after replacing it w/ rebuilt strut and it working for 2 months, the error message is occasionally there. Further, when i shut off the engine, i hear leaking sound from the front right wheel well. However, whatever is causing it obviously stops at some point as there's no sag at all. I tried replacing it w/ another airmatic strut, and unfortunately the same thing occurs. Unfortunately, now there's the "visit workshop" message is on continuously AND the comfort/sport and raise/lower buttons no longer work.
Any help would be appreciated.
PL

 

The front right wheel well has 3 components that can leak air. The strut, which you say is new, The valve block. and the exhaust. The exhaust relieves the air pressure in the system when you shut off the vehicle. I'd look there first. In my case the hose cracked broke and it made a loud whooshing noise. If you look be hind the front wheel well guard (at the front), locate the compressor. There is a fitting sticking out of the compressor (about 3/8" in diameter). There should be a hose connecting to that that runs upwards and towards the. I think the hose is about 3 or 4 feet long. At the back of the inset and above it is a noise arrestor that the hose connects to. If its the original hose its likely done.


If that is good, then check the valve block. it's located behind the passenger side headlight. Open the hood before you shut off the vehicle. Shut off the vehicle and then walk over and listen to where the air is coming from. Those lines are plastic and there is also a larger plastic line from the compressor to the block. if the vehicle is not dropping, it's not going to be the lines to the corners. but it could be the line from the compressor - soap test. I remember someone writing once that they had a cracked line at the valve block. If its the compressor line, I'd get a new one rather than try to repair it.

 

Thank you.
Mechanic said there's hose that's leaking.
It's only $30 part, but 2 hours labor plus 3 weeks to get part on order?
Good news is it's not the valve block which is over $500.
Thx again.
PL

 

bzliteyear, what was the solution to the comfort/sport and raise/lower buttons not working? Were you able to get a resolution?

 

I'm guessing the system error has disabled those controls.

 

My 2008 R350 (W251 w/ rear airbags only) is still sagging rear right side. It started out intermittently being low, then back to normal, then low, then back to normal, etc. over a 6-week period. Then it got very low/near-flat (on the rear right side only) when the car was parked for an extended period of time. While driving or with the ignition in the on position, the rear right side would raise up to 2.5-3.5 inches, while the left rear side was up to 5+ inches in height.

Things I've done since the car when near-flat on the rear right side only:
- I've looked at the orange 40-amp fuse (which was not blown) located at the front right side (under the hood);
- I've replaced the $20 compressor relay (because I didn't want to test it) located in front of the 40-amp fuse;
- I've installed a new $170 Arnott airbag/air spring (which came with nearly fail-proof, instructions within the packaging...but be careful with the white, screw-on alignment plug...this is similar to a toggle for a toggle bolt but because it is made of plastic, the prongs can easily break after several failed attempts to hang the airbag in the proper alignment); and
- As of the morning of this message/reply, I replaced the $180 air valve which is located at the front right side (under the hood) in front of the right side wheel well (given only rear airbags, my valve has only 3 brass screws with a small color-coded, white, plastic lines: red and blue lines which go to each air bag in the rear and a brown line for the compressor/air tank line).

However, the car is still higher on the rear left (5+ inches) and lower on the rear right (3.5 inches). This must be sensor (either mechanical or electrical part) and/or it may require some calibration from some MB dealership tool/computer. Anyone have any options for me at this point or am I doomed to bring the car into the dealership?

 

OK....this could be my problem: Under my ID at the benzworld forum, I reference another thread and photo. It looks like the height sensor body is attached to the bottom of spare tire wheel well. The height sensor has an arm which is attached to some other bar/lever which is then attached to the rear underside of the control arm (behind the airbag). I don't know if the left sensor is overcompensating for a damaged/bent right sensor or bent/rusty/damaged right-side bar/lever.

I'll raise the car and compare both sensors and both bars/levers. Given the sensors do raise the car, I expect to see or measure that the sensor, the sensor's arm, or that the bar/lever is bent.

But this doesn't answer why the right rear goes completely flat overnight....unless I also have a small crack in the air line for the rear right side (color coded as red at the air valve block and the airbag).

 

Our whole rear end just dropped all the way down...I mean tail-dragging. Was fine this morning, 5 hours later it's down, with big red dash light "STOP car too low" F- it... drove it anyway. (humped along like a low rider!)
Bags replaced 1.5 years ago (gen-u-wine MB) Fuse OK, relay OK, Can hear pump clicking but won't run. Why did both sides suddenly drop together? Did the compressor blow a seal and bleed down? We'll find out after our Indy digs into it and let ya know.

[caution: rant ON]
So, typical of our LemonArr, every two months something expensive fails. Gee, what a reliable car. Of course it IS high mileage: 99,700. What'll happen next? Ooh, I can't wait to find out. Ahh, we only average 8,625 miles a year, so it might be a while.
You think I'm just whining?... In 34,500 miles, 4 years, we've spent $25,500 on repairs and maintenance. Yeah, you read that right. Are we stupid? Maybe. We keep saying "Well, that's fixed, so the car is running great!"
With the 20/20 hindsight that some folks have, we'd have gotten rid of it 3 years ago. Love/hate relationship. It's a real nice POS.
[rant OFF]

 

Lowrider Update:
Compressor dead. Fuse and relay OK (strange the fuse didn't blow with frozen pump). New MB compressor $795.00, labor, $255, + supplies, taxes etc... We've just put another $1,124 into the LemonArr. But that's fixed! And it rides better than ever!! Yay! I have the old pump for dissection.
Summary update: 4 years, 34,508 miles, $26,624 in repairs and maintenance. $0.77 per mile, not including fuel. Let's see... averaging 22mpg, that's ~1,570 gals, at, let's say, $3.10/gal = $4,867/34,508=$0.14+0.77 = roughly $0.91 per mile. wow. I wish I hadn't done these figures. But, the car runs nice now!

 

And this right there is why I converted ours to coil springs.... total cost... less than $500 and I will NEVER have to worry about it again... and it rides just as smooth as a rear air spring R.....

 

Good on you!
I was going to go to coils when the first bag leaked, but I don't have the facilities to do it myself, and the Indies around here wouldn't touch it... liabilities, they said.

And, after some thought, looks like we're just gonna keep the R and fix it as it breaks. 100k mi. right now, hope it doesn't cost another $26k to get it to 150k mi. All it took was a trip to the store today... the R rides, handles and looks pure luxury. Keeping a 2x4 handy for wood-knocking.

 

The wood grain trim inside is real wood, so you can just knock on that

 

handy!

Yeah, how many of you are thinking I'm nudts?

 

Yea, BS on the liabilities... As I posted in another thread...

Mercedes of Akron's service manager looked at my install and knows the M-Class springs that cross over (the same part# used in the non air Euro-spec R) so he could have it as an alternative. It is all Mercedes parts, and in other markets you could get the long wheel base R without the self leveling rear air springs.

See, I didn't do the Jeep spring thing. I actually faked that I had an R without coils and got the part number, I then crossed that part with other vehicles it fit, and what do you know... it came up under the M-Class.

 

A week has gone by, and the rear right air bag/air spring holds pressure. This means that there are no air leaks from the air block valve, to the air lines, to the air spring itself. Research indicated that when the car is parked, it does lower itself a few inches.
Also, I raised my w251 (2008 R350) and I saw no visible problems with the sensors, the link/lever, or its connection to the control arm. Both left and right sides appeared to be properly positioned and all parts appeared to be in working order (see attached photos)

You can see the Arnott air spring I installed in one of the photo.

PeteInLongBeach helped me out at another benz forum. To his point, I should replace the other air spring and take the car in for calibration. This video provided clarity as to what is involved with calibrating ride height using MB STAR software:

 

Good to hear that your problem seems to be gone now... replacing the other rear air bag would not be a bad idea, but in all honesty, I don't think you need to worry about doing it so soon either. As long as both sides are functioning correctly, it should be ok to swap out the left bag for the Arnott replacement a little later, too. Doing them both at the same time is usually just a good way to remember when they were done...since R&Ring those bags is such a simple operation, you don't need to feel like "well, since I'm already here, I might as well do them both"

about the car lowering itself, when parking, I did not realize the non-airmatic cars did that also. I've been trying to figure out the whole airmatic logic recently, and started a thread here: https://mbworld.org/forums/r-class-w...tic-logic.html
Does your rear end lower EVERY time you park it, or only sometimes...?

I notice that your rear lower control arm also has the extended stub that lifts the lower right angle bracket that the sensor link attaches to. I posted about that here:
https://mbworld.org/forums/r-class-w...ml#post6424996
Since your car is a 2008, I am now assuming that '08 and later cars probably have this revised lower control arm, as the lower bracket on my rear links attach directly to a flat surface on the arm...very interesting...

 

I feel like a fool (and I laughed at myself)…I finally fixed my suspension problem! My car is now measuring 18.5” on both sides (a height measured vertically from the center of the wheel up to the arc of the wheel well) and I didn’t take the car in for MB STAR sensor calibration!

Discovery, Cause, and Remediation:
I just replaced the rear left with the new air spring when the wife said that there was no harm in using my bottle of soapy water against the rear right air spring. I didn’t have a sprayer bottle of soapy water when I originally installed it. So, I sprayed the brass compression fitting, the air line, and the air connection at the air valve block. I started the car and let it run for 2 minutes. Yup…I got Bubbles! I failed to fully tighten the brass compression fitting against the rear right air spring! I removed the tire, grabbed a 10mm open wrench, and after a ½ turn, the bubbles stopped. That little air leak was holding enough pressure to fool me and keep the rear right side up for several hours.

So, lesson learned…..
The original rear right air spring very likely had a hair line crack. But I failed to properly install the new air spring because I thought I sensed resistance when initially tightening (I didn’t want to over tighten) the brass screw at installation. As a result, I spent about $400 more than I needed.

Final note:
I failed to properly determine air spring and airmatic differences between different MB models, chassis, and year of production. As such, I stand corrected in that my 2008 R350 on the W251 chassis is not programmed to lower itself when parked. My car was simply lower given all I’ve mentioned above.

 

Can you give me the information on converting mine to coil. Shock n Spring part numbers along with any other parts needed to complete the job. Thanks!!

 

Here is one thread..
https://mbworld.org/forums/r-class-w...onversion.html

Forum Search will get you more.

 

Thanks!

 

Does anyone know where to search these part numbers? I'm having no luck.

 

Umm... go to any of the OEM parts sites and enter the part number...