SBC pump, pumping
09-11-2008, 06:24 PM
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2015 GLK 250 BT
SBC pump, pumping
Curious question about our SBC pump. On occasion, while stuck in traffic, having to depress the brake, creep forward, depress again and repeating this countless times in traffic. I noticed that the SBC pump will turn on and pumping up the brake lines, about every third depression of the brake. My question is why? I wouldn't think the brake pressure have "leaked out" anywhere so why would the SBC pump go on so frequently. If the pump switches on repeatedly within a few minutes, the pressure would seem to be to high 'cause there's no where for the brake fluid to goto??? Is not like when we release the brake, the pressure is released out of the system, ie. its a closed system.
09-11-2008, 06:30 PM
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It's a pretty mysterious system for sure, but the warranty on it is extended to 10 years so they'll fix it if this turns out to be a problem.
09-11-2008, 07:36 PM
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2005 E500, 2011 ML350
Normal, it is building pressure for the brake assist. Take a normal brake system car, stop on a hill and shut off the engine then roll forward.....the first time you brake it will be easy, the next time the pedal will be harder, than the next it we be very difficult to depress......
Why? Because all the vacuum assist has been drained. Restart engine and car will stop fine again. SBC pump is doing the same thing....
I hope that made sense
Why? Because all the vacuum assist has been drained. Restart engine and car will stop fine again. SBC pump is doing the same thing....
I hope that made sense
09-12-2008, 06:51 AM
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E350 Sport Package
09-12-2008, 09:04 AM
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03 E500 and Corvette
The sbc pump supplies pressure to the braking system and to prevent continuous operation and short pump life there is an accumulator. The purpose of the accumulator is to store pressure (sort of like a big spring) so that immediate pressure is available when the brake pedal is depressed when the pump is not running. If the accumulator is not at the correct pressure the pump will activate frequently. Yours might be "normal?" but it might also have an issue with the accumulator. I would suggest let the MB dealer check this out since it is your primary braking system and a potential safety item.
09-12-2008, 09:59 AM
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Eurocharged 2004 E500, Eurocharged ECU/TCU 2005 SL600, 2010 Caddy SwaggerWagon
Mine does this as well and it's completely normal. It will even do it in Park. Test it, while in park pump the brake pedal 3 times and hold it on the 4th. You'll here the SBC pump.
