2007R350guy

Hello all,

Does anyone know what part in the front engine compartment may be making a hydraulic pump inflation noise? This happens when I start the car after it been sitting for a few hours or so. I also hear a deflating noise in the front engine compartment a few minutes after the car is shut off. Any ideas?

Thanks,

Will

carpersn

If you have Airmatic, that's what you're hearing. It preps the car for driving, then lowers after you turn off. Otherwise, you could be hearing the electrical system powering on and off and mistaking that for hydraulics, as it is loud as well. Good luck figuring it out, but it definitely doesn't sound like anything is wrong

ct_r500

Yeah, I think it's the airmatic - I hear the same thing. I think there's a service bulletin on this issue.

T-B-32.22/65 Discharge Noise from Airmatic Compressor

So there might be a fix for it. Have it checked out and let me know.

lkchris

According to the text of that DTB, the "fix" was implemented in production as follows:

It's normal for the noise to occur, the DTB is just something to make it quieter.

chilledbenz

I had the same question, so during a service visit I questioned my service adviser who told me that from 2008+ all R class's have a version of the airmatic system and the noise that comes from the front end is the air compressor. The airmatic system isnt as complex as the old airmatic package, where you could raise and lower the ride height yourself, rather it does it automatically at certain speeds (highway driving lowers, in town raises). I've yet to find anything backing up this statement from MB other than the window sticker that claims "air leveling rear suspension".

veppe

I would say it's not doing the lowering/raising at certain speeds. If it's only for rear suspension, there's no reason to do it at certain speeds just for rear. So I would say it's just the auto leveling based on load. So basically the same feature since W123s but with air instead of hydraulic

y2b4sure

I thought all R-class had air leveling rear suspension, not just the newer ones. There is no scaled down version of Airmatic that I'm aware of.