2005 W211 320D 'groaning' on unlock.

[johnDut]

Hello all. Am returning here after years away. A recent purchase of a 2005 W211 320D Sport saloon with 33000 on the clock and full indy history is going well (was), until a few weeks back the car started to 'moan and groan' on unlock, i.e. before I get near the ignition, some very noisy 'pump' is running for 5 to 10 seconds under the bonnet. The noise repeats sometimes on medium to long journeys but much more briefly. It always happens however on car unlock. Any ideas? I've owned 3 other W211's but never heard such a thing before. It made me wonder if there is air suspension fitted, but the paperwork does not mention it and there are no switches relating to it inside the car.

All thoughts very welcome. Thanks in advance and hello!!

 

[220estate]

I can´t tell you what it is (maybe a vacuum pump?) but I had exactly the same thing on my previous car, a 2003 W211 270CDI. Seems to be normal, the car did this every day for the 4 years I owned it.

 

[whitenemesis]

SBC pump is on it's way out? The system will pre-charge the braking system on unlocking and occasionally during driving.

 

[PaulG]

Hello all. Am returning here after years away. A recent purchase of a 2005 W211 320D Sport saloon with 33000 on the clock and full indy history is going well (was), until a few weeks back the car started to 'moan and groan' on unlock, i.e. before I get near the ignition, some very noisy 'pump' is running for 5 to 10 seconds under the bonnet. The noise repeats sometimes on medium to long journeys but much more briefly. It always happens however on car unlock. Any ideas? I've owned 3 other W211's but never heard such a thing before. It made me wonder if there is air suspension fitted, but the paperwork does not mention it and there are no switches relating to it inside the car.

All thoughts very welcome. Thanks in advance and hello!!

As stated by @whitenemesis it sounds like it is your SBC pump. Mine does the same thing at startup and also during some driving too. On the W211 all pre-facelift cars (2002-2006) had the SBC pump fitted. When it goes it will cost quite a lot to get it fixed. I had my pump reconditioned last year.

As for your other W211's. If they were facelift versions you would not have heard the noise as Mercedes removed the pump and in the USA offered a 25 year guarantee on the pump.

 

[MD5]

I have an 04 E500 estate with full airmatic. It groans for a few seconds when unlocking after a period of non use. I've always assumed it's the compressor priming the air suspension, which it occasionally does whilst on journeys.

 

[johnDut]

Thanks all.

As stated by @whitenemesis it sounds like it is your SBC pump. Mine does the same thing at startup and also during some driving too. On the W211 all pre-facelift cars (2002-2006) had the SBC pump fitted. When it goes it will cost quite a lot to get it fixed. I had my pump reconditioned last year.

As for your other W211's. If they were facelift versions you would not have heard the noise as Mercedes removed the pump and in the USA offered a 25 year guarantee on the pump.

all the others were after 08 so that explains that. Sounds exactly like the SBC then. I'll get a diagnostic run on it locally and see if there any fault codes, if not, learn to love groanng!

 

[johnDut]

and to complete this thread, Local MB indie confirms all the above, and the diagnostics show nothing wrong. Apparently MB released a vehicle that groans loudly when you unlock it. Who know that was possible??

So I'm puzzled by at least prepared to live with it. I just cannot imagine MB signing this off. Maybe the pump is silent when new and starts getting noisy as age sets in. The car is 19 years old I guess, so??
Anyway. Thanks for all the help.

John.

 

[mersum1es]

Yep, SBC pump ensures you have enough pressure in brake system when car is waken up. Its totally normal to do that, though if it does it every time no matter how short time it has been sleep, it might point some minor leak in system. It is not fully silent even as new, and there was 'silencer' kit available for first lineup models but I would think it is already installed from factory to 2005 cars.