SBC pump and the AUX battery

[VipZ]

Can anyone tell me if the SBC pump is run by the aux battery?
When I'm driving I can hear the pump kicking in and this evening I parked my car on the drive turned engine off and I heard the pump running.
The guy down at the Merc garage said it was normal for this occur because the pump is constantly making sure its working!
Any views on this?

 

[Dieselman]

It uses the small support battery and is active while the CAN is live.

 

[VipZ]

Sorry dieselman, don't want to sound stupid but what do you mean by CAN.

 

[Dieselman]

Control Area Network.

All the electronics of the car run on a network. The SBC stays working while ever the CAN is still awake, about 20 minutes after locking the car.
You can tell the CAN is awake because the dashboard LCD is on.

 

[whitenemesis]

Is it different for the CLS then? WIS shows the aux battery simply as a support for the main battery with no direct connection or function related to the SBC.

 

[mersum1es]

W211:
http://www.mercedestechstore.com/pdfs/W211_technician/319 HO Dual Battery (ACB - ICC) 11-29-02.pdf

I've thought that W219 is similar...

 

[whitenemesis]

W211:
http://www.mercedestechstore.com/pdfs/W211_technician/319 HO Dual Battery (ACB - ICC) 11-29-02.pdf

I've thought that W219 is similar...

So, pretty much as I understood from WIS.

 

[VipZ]

So going back is it normal to hear the pump noise all the time. It's not the quietest of noises. Is anyone else experiencing this?

 

[whitenemesis]

Not all the time. Should just kick in and out as required to maintain pressure. Can't say I've heard mine once the IGN is off.

 

[effbee584]

So going back is it normal to hear the pump noise all the time. It's not the quietest of noises. Is anyone else experiencing this?

It should not be on 'all the time' but its frequency of operation may be due to brake use in your driving style.

On my W211 220cdi, it did operate quite a lot, but less so on longer steady speed drives. SBC was really noisy when it operated, sometimes just turning on ignition on a quiet morning it sounded like there was a cow under the bonnet, and it was audible while driving - I learned to live with it.

The W211 320cdi was just about audible, which I understand was due to a different length and routing of piping to/from the SBC pump in a different engine bay layout, so much quieter that I forgot about it.

I understand that MB brought a modification to the piping that reduced the noise significantly. Can anyone add more info for VipZ.

 

[VipZ]

Thanks for that bit of info. I wonder if the SBC pump can be reset so it can learn my driving style. I've only had the car about 4weeks. So not to sure ow the car was driven previously.
Also Merc garage said they have some new piping which can reduce the noise down a little. I'll have a look in to that. Unless somebody has already had this replaced.
Thanks effbee. Great help. Confirms what I've read on the net and what I've been told by the Merc garage.

 

[Harrythedog]

It should not be on 'all the time' but its frequency of operation may be due to brake use in your driving style.

On my W211 220cdi, it did operate quite a lot, but less so on longer steady speed drives. SBC was really noisy when it operated, sometimes just turning on ignition on a quiet morning it sounded like there was a cow under the bonnet, and it was audible while driving - I learned to live with it.

The W211 320cdi was just about audible, which I understand was due to a different length and routing of piping to/from the SBC pump in a different engine bay layout, so much quieter that I forgot about it.

I understand that MB brought a modification to the piping that reduced the noise significantly. Can anyone add more info for VipZ.

http://www.mbclub.co.uk/forums/wheels-tyres/87806-w211-sbs-pump-noise-solution.html

HTH