Diesel-King

Hi,
I own a 2008 R320 CDI 4matic with the Airmatic suspension on all 4 wheels.
The front of the car is sagging every now and then after being parked and left unused.
Only the front is sagging. And both sides are sagging at the same time.
Some times the car sags just the next day, and sometime it takes 6 days until it drops to the floor.

I've changed the valve unit, but it did not solve the problem.

Could it be the front air bags? If so, why do they keep up for several days and do not sag immediately?

Why do both air bags sag at the same time?? It's not likely they went bad at the same time...right?

Today I "cought" the car lowering itself slowly...There was an air-leak sound
coming from the left front wheel area....I sprayed soap/water all over the place but did not find any bubbles...not from the air bag, not from the reservoir....
I started up the car, and it went fast to normal hight...turned it off and left it parked...6 hours has passed since, and it still maintains normal height....

Could it be something else??? Could it be an electrical problem, like a peel-off of a cable connecting to ground sometimes and the Airmatic
CPU opens the front valves?? Or am I becoming paranoid....???

PeteInLongBeach

Asked and answered several times on the other site (starting at post 44) :

http://www.benzworld.org/forums/w251...problem-5.html

Given your description, I assume you are the same person. Even though you are desperately trying to avoid it, just replace your front air springs with Arnott units.

Diesel-King

Yes, I decided to write a separate post with my problem so people can better trace the fault symptoms and solution (if I finally find one...)!!

And now to your second comment:
I know that I can change the air bags to Arnott ones...and I just might do that but only when I'm sure that it solves my problem..

houseofdiesel

If you want a proper diagnosis go to a shop that has the star system (dealer or really good specialists) and have them check faults and run an output test on the air suspension, I am not that knowledgable yet on the R class set up, perhaps if one side has a serious leak it drain the both, not sure. Rise your suspension to the high setting and recheck for leaks, wipe the front struts down with a wet rag to remove any little stones etc. Look for corrosion around the fittings (unlikely but possible).

Diesel-King

Thanks for the tip Houseofdiesel...

The other day, finally, I found a tiny leak in the front left air bag.
It was just above the "rubber fold".
I sprayed soap/water on it and out came small bubbles...

The strange thing is that sometimes , even with the damaged lair bag, the car can stay up several days.....sometimes just one morning, etc...

I've not managed to find the leak in the right front airbag....perhaps it lowers also when the left one does...perhaps as a "precaution mechanism" by the car itself???

I'll take out the battery nect time and see if it holds or sags, and report back in a day or so...

PeteInLongBeach

There is no such "precaution mechanism". Your air springs are old, used, leaking (even if you can't locate the other leak), and at the end of their expected life. Just replace them - you are only wasting your time playing with it at this point.

starbound01

I thought I woudl contribute something....

I had the rear of the R500 fall and replaced the rear with Arnott. Very easy with a little patience and only had trouble seating the tube into the unit. It popped out twice before I got it right. Use LOTS of pressure to seat it.

To add input to this thread; When i was diagnosing the proboem, I found information that spoke to the fact that the compressor itself can fail from running all the time as a result of ignoring suspension air leaks. In the case I read, the wire harness was also damaged along with the compressor. No clue what a wire harness would cost but I bet is very expensive and a compressor is about $500. Rear bags are under $200 each and it will take longer to jack up the car and remove the wheel than replace the bag. The front struts are $500 ea after core charge. Not sure how big a job it is.

PeteInLongBeach

Arnott has replacement instructions available for viewing online. For example :

https://www.arnottindustries.com/par...18_pid190.html

https://www.arnottindustries.com/ftp...%20REV%203.pdf

Gordinho80

Hello,

My parents have a 2007 R320 CDI. The driver side of the car has been lowering recently, 2" lower than the passenger side.

I've not had a chance to really look at their car yet. Last time I had a quick look, I thought I saw actual coil springs and not airbags.

Are there airbags as well as coil springs on these cars?

I can say with 100% certainty, if there are airbags, they've never been replaced.

Any help is greatly appreciated.

Mario

Diesel-King

Replaced front left stout with MB original part (bag + stout). Problem resolved!!

The car is not lowering on the right side when parked overnight, so I guess it's not damaged.
Seems that one OK strout can not take the car's total weight if the other air bag leaks..

Mario: It's either air bag or coil, but not both!!

starbound01

You might as well plan on replacing the other one too. These air bags get a lot of abrasion between the base of the strut/can. there is a lot of dust, sand, junk that gets in there and the rubber is almost constantly moving. People try to do the soap test but that rarely works becaues its dependant on the position of the body and how much of the rubber is exposed and the size of the pinhole.

Anyway, all the bags are exposed to the same grinding. Bag failure is inevitable and all cars, regardless of make, that have pheumatic bags experience this same problem. The rear on my R500 went to 90+K before failing and the failing was 1 oe 2 times over 2 weeks. I replaced both bags, problem gone. But I didn't use MB orig parts, I used Arnott. I think they have a lifetime warranty.

Gordinho80

Any idea what might cause driver side to be intermittently be lower than the passenger side (with coils)?

My father claims that if he sits with one leg outside and starts the car, it comes up about 1/4"-1/2", but not back up to level.

This one is strange. Add to that, we recently had the dealer give it a full inspection and repair some items that needed attention. They made no mention of the suspension.

Diesel-King

Yes, I'm planning (saving!!) to replace the other strout too. As you say, it will likely begin to leak soon as well...

I did not go for the Arnott bags since my strouts have 95.000 kms...and they were likely to fail soon due to gas leakage...It's a pitty MB does not provide strout + air bags separately....

Diesel-King

Have you checked the rear suspension?? Maybe you have air bags in the rear that have a leak....I've read that some cars come with auto-levelling system in the rear (=2 rear bags?)...I'm not sure though...Mine is Airmatic (= 4 bags, and no coils).

Gordinho80

Thanks! I'll have a look at the rear.

jmsar320

All,
I have read already about other similar cases where most of the recos are to replace the airbags with Arnott units.
Please advice if that is the same recommendation for this case:

R320 2008 that I bought with 72,000 miles started having air suspension problems at 110,000 by sagging on the right (Passenger) and the rear side. Problem has been intermmitent and started happening in late March at the end of winter. Sometimes, when parked, the car would lower only on the right rear side, sometimes it would lower both sides in the rear.
Also when the car is started, the car raises that right rear side that is sagging but it never makes it to the same level of the left side.
I measured height with a measuring tape and the difference is 1.75 inches lower on the sagging side. There is also a smaller difference at the front of about 0.75 inches.

I've used the car now for about 2 months with this issue since my local shop doesn't find the root cause of the issue and it is starting to wear the right front wheel uneven versus teh other left wheel. They have checked the compressor and air bags indicating that they are OK and they have replaced airlines and fittings in the airmatic system.

I have the dilema of replacing both Rear Air Bags using Arnott units versus converting to Springs??? What is your advice?
I am sick and tire of this issue and roads in Pennsylvania don't help.

Thanks,

JM

PeteInLongBeach

When the suspension starts settling like this, it is almost always a leaking air spring (rarely a valve in the valve body). "Checking" the springs (whatever they meant by that) is not always conclusive in finding leakage. At the mileage on your car, it is certainly air spring leakage (even if it isn't, they are due for replacement anyway).

The airmatic springs should be regarded as a consumable, like tires and brakes. Always replace them in pairs, as the other side will fail shortly after. The rears are simple to replace, the fronts require more mechanical aptitude. Arnott has detailed instructions and videos for the replacement procedures, and these must be adhered to. Make sure your service agent has experience in replacing these springs, especially the front units. Ideally, they should have a STAR machine in case recalibration is needed, but the calibration should be OK if the system has been disabled properly per the instructions.

jmsar320

Thanks to Pete in Long Beach,
Your recommendations worked perfectly.
We replaced the rear air springs with Arnott equivalent parts and the car has been riding perfectly for few days now. They also had to replace a leveling sensor on the passenger side in order to fix the 1.5inches height difference with engine and air compressor running, and the car is now perfectly leveled.
Thanks for all the hints and technical coaching.

JMS