Bronco Badlands - My Brakes are Releasing from a Stopped Position - When on a Hill

[mrdibbles]

Hi Forum,
My Bronco Badlands (SAS + LUX) is at the Ford Dealer and has been there for going on the 3rd day. It has less than 600 miles on it and it was selected by Ford at random for a 20-mile quality control check (there was a piece of paper in my glovebox citing this) at the factory.

Anyway, I took it into the dealership after experiencing, at least a half dozen times, my Bronco's brakes releasing, from a stop with my foot on the pedal, causing the vehicle to slowly "slide" down my driveway. At first I thought is this right... is this supposed to be happening. Then... I realized heck no... this should never happen.

My driveway isn't what I would call steep, but it is on a slight hill, and given this is Florida (no snow or ice) and also given my driveway is made of pavers that are dry, there is no reason my vehicle should give me a sensation of "sliding" while I am depressing the brake pedal sufficiently. The scenario as I explained it to the Ford Service Department:

1. Backing slowly, or pulling out Forward slowly to the edge of the street.
2. Coming to a slow stop with the foot gently and adequately depressed on the pedal.
3. Checking right and left for cars and/or pedestrians before proceeding.
4. The vehicle would cease being stopped, the pedal would go soft, and the vehicle would go into an uninvited slow & stuttering roll into the street.
5. Yes I did have, on two occasions, cars transiting behind my vehicle.
6. The Bronco only took my command to stop when I mashed the pedal to the floor as in an emergency stop.

Thus far the Ford Service Department is suggesting the culprit is electrical with the ABS, they did replicate this, and they are trying to chase it to figure out what is at fault.
Has anyone else experienced this?
Thanks,
Matt

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[JediMcMuffin]

Ummm.. yikes.. Keep us posted! I assume you're driving in normal mode in 2H?

 

[Captain nSANEo]

When the Bronco starts to "creep" does your break pedal go squishy? If so could be air in the brake line.

 

[mrdibbles]

I will keep the forum posted. Yes on me driving in 2H and the Ford Service Department ruled out Master Cyl., air in lines, and/or leak in brake lines.

 

[ATLBronco75]

vacuum leak

 

[TXNavy]

Or another ABS module going faulty. Seems to be a common occurrence lately but I know that is not true, just a factor of reporting bias to an enthusiast forum. Does look like maybe Ford got a bad batch of ABS modules from a supplier though.

 

[R.A.N.M.J.]

vacuum leak

My first thought too.

 

[mrdibbles]

The Ford Service Department manager just called me. Ford's Technical Hotline, which is the centralized forum for Ford Service departments to consolidate Bronco mech/tech issues, appears to be citing the Electronic Brake Booster as the culprit. He will call me back later today with more on that and a lead time on when that will arrive. He does not have that part in stock.

 

[mrdibbles]

Check out this report from Ford Authority. Sounds like a similar issue on 2021 Ford F150. The description of the situation seems to closely align with my experiences.

https://fordauthority.com/2021/07/2021-ford-f-150-recalled-over-safety-issue-with-brake-booster/

 

[WuNgUn]

My first thought too.

You were still have mechanical hydraulic pressure on the brakes, just not boosted.

 

[WuNgUn]

Unfortunately you will not with EBB systems as an electric actuator drives it and the brake pedal is basically just a signal. There is a chance to move it manually but it is very very hard to do so.

You mean there isn't a hydraulic master at the pedal??

 

[Paul Gagnon]

Unfortunately you will not with EBB systems as an electric actuator drives it and the brake pedal is basically just a signal. There is a chance to move it manually but it is very very hard to do so.

I don't think the regulations allow that. The mechanical braking system has to be fully functional if any electronic component fails. You may have to push the pedal harder but you should still have brakes.

 

[flip]

The pedal is still mechanically connected to the reservoir. EBB only supplies assist like the vacuum set up. For the OPs issue, I'm going to go with a bypass or dump valve open in the HCU. Could be a mechanical issue or initiated by a faulty reading from one of the sensors/switches/motors in that system.

A loss of assist will not cause creep, just a hard pedal or increased pedal effort. Creep is caused by leak, air or part of the system bleeding off fluid pressure from one or more of the circuits.

 

[The Pope]

All I'm going to say it that a Mechanical Hand Park Brake Leaver would have been nice to have had in any vehicle that this type of situation can even remotely happen......

@Ford Motor Company, you now that you messed up when you went the "lets electrify as much as possible route..."

 

[flip]

This is what I'm seeing in the WSM.

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