Is there a vacuum powered brake assist on SBC?

[Norse]

Hi.

Had a little scary experience during the christmas holiday. Started the car it was -20 degrees Celsius, let it idle for about five minutes before I started to drive, and when I tried to brake at the first intersection I had NO BRAKES.... Went to the dealer who of course had never heard about this before...
The guy I talked to said that maybe there was a lack of vacuum in the brake assist system.. I had been under the impression that the SBC brake system was pressure operated, and that there was no vacuum assist on the pedal..
Am I way off ? ? Or is he yanking my chains?

 

[Justin1600]

If the SBC system fails, then the brake pedal will go down a long way ( which will feel like it is going to the floor ) but there will be a hydraulic brakes at the bottom of the pedal travel that could lock the front brakes if enough pressure is applied

 

[corned]

Two things spring to mind here.

Firstly, I didn't think SBC brakes were vacuum operated.

Secondly, diesels don't have inlet manifold depression-derived vacuum in the first place (no throttle!), so there would need to be a different way of doing this, i.e. a belt-driven vacuum pump as an ancillary on the engine. As far as I can tell, there is no pump on the CDI engines, but someone will surely be along to confirm/deny that.

If there is no pump, then he's yanking your chain...

 

[Norse]

Yepp.. That's what happened.. But after that the brakes were fine, and have been ever since.. Just didn't like the whole incident.

 

[Justin1600]

Yepp.. That's what happened.. But after that the brakes were fine, and have been ever since.. Just didn't like the whole incident.

Did the garage carry out a Star Diagnostic short test on the vehicle, and check the service scope of the SBC unit, sometimes the unit needs to have it's software updated. Or the unit might need to be replaced, the Star diagnosis will tell them that

 

[Norse]

Did the garage carry out a Star Diagnostic short test on the vehicle, and check the service scope of the SBC unit, sometimes the unit needs to have it's software updated. Or the unit might need to be replaced, the Star diagnosis will tell them that

No.. No diagnosis yet.. Just went to talk with them.
I know I need to have on done, but wanted to hear what they had to say first.

 

[Satch]

SBC system depends on an electric pump to produce the pressure: that is the BRRRRRRRRR noise you get when opening the car up. The person you spoke to at the dealership clearly knew nothing about the SBC system but was happy to fob you off all the same.

Now it could be related to extreme cold in some way but even so first thing should have been to put it on a diagnostic and a mechanical inspection.

MB is very, very sensitive about SBC related problems worldwide and your dismissive treatment is nothing short of an utter disgrace.

 

[trapperjohn]

http://www.mbclub.co.uk/forums/whee...brake-failure-mercedes-c220-blueeffiency.html

^You are not the only one to suffer this safety issue Norse.