ertech

Rear of the car is real low after one hour parked on both side.
This is what i did so far to diagnose.

1-used the search function

2-sprayed soapy water on the fitings at the pump, rear bags, rear reservoir ( no bubbles)

3-used my mb star and did all the tests in airmatic section ( no problem)

In the back the 3 lines ( l and right back and reservoir )go into the floor .

Where do they go?

On a side note when i jacked the car from the hitch the botton of the left bag was not seeted and could be moved around and not hard or inflated.
Can this be my problem?

If one bag is bad can this cause both sides to lose air?

Thanks for any help or guidance.
Erick

What should i check next

alx

Could be a few things.

However, the airbag should be impossible to move/ remove when installed even if that wheel is off the ground. The bag should be wedged there. If you can move it by hand then there is no pressure in it.

And yes- failure on one side can lower both sides- however one will be lower. Park on flat surface and when happens check height sensor values in das. The offending side will be a couple mm yet lower.

One thing to do is perform automatic leveling in das and see if it finishes successfully.

My take is that you either have a bad airbag or valve block and you have a slow leak somewhere at or between those two components.

It is also possible that you have a leak at the air dampers.

Get a mechanics stethoscope and listen around the valve block or the airbag - especially around the hose fitting.

ertech

Is the block right under he headlight?
What is the dampers?
Where in das is the auomatic leveling?
Thanks

alx

do not know where the valve block is on the gl - but historically it has been a failure point for the airmatics hence my suggestion

the dampers are a pair of reservours. #8 on the diagram

http://www.parts.com/parts/2007/MERC...agramCallOut=1

the automatic leveling is under "airmatic", "actuations", "move towards .... (Automatic)". it will take a few minutes for the calibration to finish successfully during which time the truck will move up and down. be patient and wait for the "complete" message.

vntgspd

Valve block is directly above the pump which is located in front of the passenger front wheel.

You have to pull the fender liner out and you will see it but it's hard to get to. I was able to leak test mine without removing it though.

Are you getting a "airmatic message" or error code?

ertech

No error code
Thanks

ertech

Just found the problem had a real slow leak from the fold in the rear air spring
Only leaks when the tire is on the ground
Thanks for the help

KrustyKustom

Have you replaced the whole air spring assembly yet? Curious as to how difficult it was?

alx

It is very easy, but you need das to depressurise the airmatic. That is if your airbag is still holding air. If it is leaking or has exploded and is shredded to pieces this obviously is a moot point

Once done, you remove the air hose connector. Then put a little jack with suitable adapter under the center of the airbag in the bottom (the lower control arm has a hole in it so you can push though it) and jack up to dislodge the airbag from the lower control arm. The airbag is usually stuck on your lower control arm.

Then unscrew the plastic guide on the top- those are single use and you need a new one which usually comes with the new airbag. They can be also have for pennies from the dealer.

When installing the new airbag make sure you don't cross thread the air hose adapter- it is very finicky and easy to cross thread and then you will need another airbag.

Lastly via das pressurize the airmatic or just raise the truck from the dash.

To summarize- if you are replacing a functional airbag- you need das. If airbag is dead and does not hold pressure- you can get away without das.

ertech

Will order the parts monday
Looks pretty easy from what i see the best place to raise the car for this job is from the hitch
Will let you know how it does
Thanks

KrustyKustom

I like the airmatic system, however I have wondered if you could convert to steel springs? I know the ML and the new Jeep share the same rear end and they have steel springs. Interesting to think about.

alx

You can. There are kits. But you lose the ride height control and also the rear gets -very- bouncy.

One last thing- if you are going with aftermarket airbags you need to calibrate the airmatic with das. If you are replacing just one oem airbag with another oem airbag- you can get away without calibration.

Do not mix up oem with aftermarket airbags. If going with aftermarket- replace both.

KrustyKustom

Thanks for your input on mixing a aftermarket bag with a stock Thyssen Krupp bag. Anyone studied a OEM and one of the american made aftermarkets? Are they a good quality bag and assembly? I am a fix it once right guy and keep my rides for a long time (try to get my moneys worth!)

Brand X DAS systems mostly the same also? Gotta get one..dont know which i should trust?

vntgspd

Here is some basic information that is nicely laid out:

https://www.arnottindustries.com/fil...620&Size=SMALL

My understanding is that you don't need StarDAS to do this repair, although it is preferable.

After lifting and securing the vehicle and removing the compressor relay, you can deflate the bag by SLOWLY loosening the air line fitting until air begins to escape. When air has normalized you can remove the fitting and air line completely and then compress the bag for removal.

Also, I realize that ALX has much more experience than I but I do not understand why reprogramming is required after bag replacement??? The bag pressure is based on ride height as measured by the ride height sensor. The system will inflate and deflate the bags via the pump and valve block until the desired height is achieved. It doesn't care about nominal differences in bag volume which is why replacing only one side would be okay as well (although I personally prefer to replace all springs and shocks in pairs).

alx

The airmatic is far more than a simple inflator. It is a dynamic system that can react fairly quickly based on multiple sensors input. The deflection rate and firmness of each airbag brand is different at the same psi. When you calibrate the airmatic the software tests rebound and dampening of each airbag individually based on slow and quick changes of pressure.

If you just replace one airbag you will have asymmetrical dampening / stiffness and in addition airmatic will not be aware of the different behaving airbag. This might affect negatively the handling.

vntgspd

ALX - great explanation. So perhaps this would explain why the car feels floaty and soft during city driving but fairly tight and capable in mountain driving and high speed freeway ramps, etc.

So, you CAN replace bags without the StarDAS but you won't be getting full performance out of the system. Those with a calibrated butt dyno and like to DRIVE (like me) may notice the difference but I suspect the average driver (like my wife ) may not.

Good thread. Hoping there will be more of these as time goes on...