y2b4sure

I've noticed that with my key turned to the final position before starting the engine, that my SBC unit is making a whurring / buzzing noise. I've read all about the various noises that SBC makes, but is it right that this noise continues for as long as the key is in that position?

I thought the noise might come on when the driver's door was opened, or last a few seconds after switching the ignition, but this noise just carries on?

Thanks in advance.

y2b4sure

I've just looked a bit closer, the noise is coming from a black 'thingy' in front of the sbc pump. It has two pipes and an electrical connection. The writing on it says Bosch PAD 12v. What's that?

TPAbnz

Normal.

SUNILP

totally normal on SBC systems

konigstiger

To deminish the humming/buzzing noise during pressure buildup from SBC system:

Under warranty:
Mention DTB P-B-42.46/27e the single suction damper is being replaced by a suction hose with integral double suction dampers (part # A2114208826). In the process, they will bleed the SBC system with Star Diagnosis.

Out of warranty:
Make sure all service campaigns and recalls have been applied to your vehicle, have the SA check your VIN in VMI. Normally only service campaigns and recalls do not expire - honored always. DTBs are only honored under warranty and/or extended warranty. However, in this case a part was modified for better brake performance (i.e.: eliminate noise) therefore, it may be worth your while to request a no cost goodwill repair from dealer and MBUSA.

If you want a copy f the DTB to present to your SA private mail your email address.

Television

The SBC pump is on the wake up circuit, when ever the car thinks that it is going to be driven, the pump will charge the system, just in case

y2b4sure

I did a bit more research and it's not related to SBC. It's the coolant recirculating pump. I think it is related to the REST feature, that I've never used.

I'd never noticed this pump running when the engine wasn't before. I found some articles that suggested it would run for a while after the engine has been running to prevent hot spots, that sounds fair enough. I'm going to see if the pump runs when the engine is cold, if it does, then that's daft.

Miguel

I'm looking for the reason why my w211 220cdi does not start. in fact that pumps runs too much time when the key is turned (before ignition). is there any possibility of having a leakage in the pipes? do you have any scheme showing that circuit?

Diesel Benz

I did not find any post about your car starting problems, hopefully comes on a separate thread.

You should be able to check the brake system pipes for leakage but if that was the case, you would also see it from the fluid reservoir. It must be more internal leak from the SBC pump valves.

The SBC brake system spare parts are the same as on other models (brakes may be different). If you look at EPC, you can find the right part for your car and also see which other models use the same part.

A bit outdated EPC copy hosted by this Russian site if you cannot have on-line access:
http://www.detali.ru/cat/oem_mb0.asp?TP=1