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Brakes dead while battery dead


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6 replies to this topic

#1 OFFLINE   CMax-Traveler

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Posted 04 August 2014 - 01:45 PM

Had a bit of a scare with my C-Max during one of my dead battery occurrences.

 

The dealer recommend I tow the car to them, without jumping the car.  So, after much hassle (ex: the tow truck didn't fit into my driveway; the shift lock release isn't where the manual says it is), we managed to load it onto a flatbed and off to the dealer we went.

 

Got it to the dealer and it was time to unload it from the flatbed.  Stepped on the brakes to gradually ease it off the flatbed and released the e-brake - the regular brakes don't work!  Fortunately we were able to grab the e-brake before my rapidly-accelerating car slammed into the car behind the flatbed. *WHEW* :drop:

 

So... if your 12v battery is dead, be forewarned - the regular brakes will only work once.  After you apply the brakes once, you'll only be able to use the e-brake.  Seems like a bit of a design / safety flaw to me.









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#2 OFFLINE   fotomoto

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Posted 04 August 2014 - 02:10 PM

You still had brakes as the e-brake sort of proved.  What you didn't have was powered brakes.  You'll really need to mash HARD on the pedal to get any stopping power just like you have to crank hard on a steering wheel without power assist.  


  • JAZ and hybridbear like this

#3 OFFLINE   wab

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Posted 04 August 2014 - 05:14 PM

You should see our

Blue Ox Patriot Supplemental Braking System

Cycle 3 times during the setup process  every time we tow the cmax.

Check this YouTube from Blue Ox, it looks JUST the same on our C-Max.

 

https://www.youtube....VlCE_H3HNY#t=20

 



#4 OFFLINE   CMax-Traveler

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Posted 04 August 2014 - 11:30 PM

You still had brakes as the e-brake sort of proved.  What you didn't have was powered brakes.  You'll really need to mash HARD on the pedal to get any stopping power just like you have to crank hard on a steering wheel without power assist.  

 

I'm not sure about that... I stomped HARD and I'm pretty sure it went all the way to the stopper without resistance, and without any braking.  But I'll have to try it out again next time my battery dies to be sure.



#5 OFFLINE   jdbob

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Posted 05 August 2014 - 12:44 AM

Here's what little the ABS operation part of the workshop manual has to say:

 

"During certain braking events, the friction brakes can be applied directly by the driver. The brake booster push rod is equipped with an adjustable stop, once the brake pedal travels far enough to engage the stop, the brake booster push rod is forced into the master cylinder and the conventional friction brakes are applied."



#6 OFFLINE   hybridbear

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Posted 05 August 2014 - 09:38 AM

You still had brakes as the e-brake sort of proved.  What you didn't have was powered brakes.  You'll really need to mash HARD on the pedal to get any stopping power just like you have to crank hard on a steering wheel without power assist.  

I agree. The vacuum pump in the C-Max is electric. So with no 12V battery you didn't get the vacuum assist. The brake pump is the buzzing you hear when you walk up to the car & unlock it. Usually when the car has been sitting for hours the pump will engage when you unlock it so that the brakes will have pressure once you turn the car on.

 

This is no different than what would have happened in a conventional car with the ICE off. You just have to mash the pedal to the floor and you'll get limited stopping power.

 

My first car was a 1998 Chevy Lumina with almost 200,000 miles. One day I was driving along and stepped on the brakes only to find that I had to really press hard to stop. After driving a few more blocks I could tell that I had a vacuum leak and thus wasn't getting the assistance I was used to from the vacuum system to apply the brakes. I found that by shifting the car to Neutral & revving the engine I could create enough of a vacuum to stop safely by using my right foot on the gas & left foot on the brake. I turned off the busy road I was on at the first safe place to do so & called my Roadside Assistance through my insurance company to tow the car. That was a scary experience.



#7 OFFLINE   drdiesel1

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Posted 05 August 2014 - 10:30 AM

No power.........No brake assist. It's simple and just the same as any other car on the road today.

You had one assisted brake application due to the remaining vacuum on the booster. After that

was used it became unassisted.  Conventional ICE vehicles are the same way. Without running

the engine you have nothing to produce more vacuum and the booster will only hold enough for

the one brake application. The C-Max had no way to activate the vacuum pump without 12 volt power.


Edited by drdiesel1, 05 August 2014 - 10:35 AM.







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