Brake failure - the Mach-E is not reacting to the brake pedal

[Breinholm]

@Mach-Lee
I just realized that we have another specialty here in Denmark: Most of us have mounted a Tow-bar and I think it is present on the bus system as well.
Thanks / Peter

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[Breinholm]

@Mach-Lee
I just realized that we have another specialty here in Denmark: Most of us have mounted a Tow-bar and I think it is present on the bus system as well.
Thanks / Peter

@Mach-Lee
Forget about the Tow bar. I made a survey on the Danish Mach-E Forums. It shows that there are 60 % of us driveing with the tow bar that have had no brake problems and 60% with the Tow bar that have had brake problems - So it has no influence.

 

[Breinholm]

OK, I spent some time reading the Danish news articles and Facebook group about the issues. Here's what I can surmise:

• There have been several articles in the Danish press about the issue in the past few weeks.
• When it occurs, there is a lack of deceleration and owners report the brake pedal is either "hard" or "falls to the floor" (could be imagined due to panic)
  • Some have said they had press really hard on the brakes
• Only a small percentage of owners have reported an issue (~60 in a country that has 3600 Mach-E's)
• There is a strong correlation (~80%) with wet conditions, either driving on wet roads or after a car wash
• The braking issues were not prevalent last year.
• Some have reported the braking takes a few seconds "to kick in"
• Ford Denmark is trying to figure out the issue, but there are not enough detailed accounts and the dealers aren't finding anything wrong.
  • In the meantime, they are telling customers they may need to press the brake pedal harder if they experience an issue.
• There is a lot of fear and paranoia surrounding the issue, some people won't drive their Mach-E.

Based on the above, the most likely explanation seems to brake surface contamination, software, or a combination of both.

Because the brakes are not used much on the Mach-E, they are susceptible to surface contamination, rust, and lack "pad transfer" on the rotor surface which impairs the friction coefficient. Whenever I wash my car or drive in rain, there is quite a bit of flash rust on the rotor surface that needs to be cleaned off during the next drive. The best way to do this is to put the car in neutral (N) and apply the brakes a few times until the brakes feel smooth and quiet. Sand getting in the pads could also be another factor (I think they use more sand than salt in Denmark?).

The problems in Denmark are very similar to this topic: Wet brakes after carwash; I can’t stop my MME

Wet brakes will have less initial stopping power until the pads have had time to clear off the water. Soap or other chemicals present (e.g. road treatments) on the rotor surface could reduce friction further. A contributing factor may be the brake calibration on the vehicle, which can limit brake pressure in certain situations such as low speeds (to avoid abrupt stops and blend with regen). In a regular vehicle, if you had wet brakes you would just press the brake pedal harder and get a proportional increase in force, but with the electronic brake booster on the Mach-E, pressing the pedal harder doesn't always equate to increased pad force. You sometimes have to press the pedal WAY harder to get a substantial brake force output.

The latest powertrain/ABS software (6.6.0+) seems to be pretty good with the brake pressure curve and feel, so hopefully once that makes its way to Denmark the complaints will subside.

To summarize, I don't believe this is brake failure. It's reduced braking effectiveness under certain conditions. If you feel like the car isn't stopping, YOU NEED TO PRESS THE PEDAL HARD SOMETIMES to eat through the water and contamination on the pads and rotors.

I would also recommend scrubbing the rotors weekly by performing several 100-0 km/hr stops in Neutral (N) until the brakes feel smooth and quiet. Also do that if the brakes look rusty. This should keep the brake rotors in good condition for optimal brake effectiveness.

Also tagging @Klokkeriis

Thanks for your first-person report. To clarify, when I say last year, I mean before about June 2023.

I have a possible idea what might be going on. If you step on the brake pedal while the car is fully asleep, the pedal will be hard. When you wake up the car, the pedal will suddenly get soft and drop because the servos become active and valves open after the ABS hydraulic control unit (HCU) initialization (when you wake up the car, the cyclical clunking noises you hear are the HCU initialization). I'm guessing the pedal drop you felt was like that. Try sitting in the car for 15 minutes without opening a door, then start it, you'll be able to feel the pedal drop after you press the start button.

If you happen to be pressing hard on the brake pedal during HCU initialization, the pressure will prevent the valves from opening and the brake pedal will stay up and remain hard until you release pressure, then it will go down. This could potentially explain the "hard pedal" reports. I'm not sure if this "hard pedal" state will prevent pressure from reaching the caliper pistons or not.

If HCU initialization is the cause, the question is why is this happening while driving? It shouldn't. But, if there is a communication disruption on the CAN bus networks, that could cause the HCU to re-initialize. If you are getting CAN-bus communication failures while driving, that is an issue that should be investigated because that could cause the brakes to act weird. It could be buggy software or some kind of wiring/connection issue.

People that experienced the brake failure should be asked if they had any kind of warring messages about collision system, radar, or ABS system pop up on the screen shortly before the incident?

If anyone experiences a similar situation and pressing the pedal hard doesn't help, quickly release the pedal and try pressing it again.

I have done a survey on the Danish Mach-e Brake problem forum.
Questions:
1. Did you drive for a long period without using your brakes before the incident?
2. Were there a larger amount of water present at the incident?
3. Did you coast the car (releasing your accelerator) before the incident?
4. Did you have pop-up messages at or around the incident?

This is the resulting reply chart:

I also asked if the Mach-E had a tow bar installed. It turns out that 60 % have and have had the failure. 60 % have also the Tow-bar, but have NOT had the failure. So, lets forget the Tow-bar.

Hope this can be helpful.

Thanks / Peter

 

[MNevan]

I just had a similar experience about four hours ago during normal conditions (dry and daylight). I was approaching a red light that controlled an on/off ramp intersection where a rural road intersects a state Highway. I was on the rural road. As I started braking, the pedal almost
immediately felt soft. I kept pressing (never pumped) the brake pedal steadily lexpecting to feel more normal resistance. The brake pedal traveled more than double the distance that it normally does. I started to get some braking, but I don’t think I could have locked up the brakes if I wanted to. The emergency braking didn’t engage; however, there wasn’t a car traveling in my lane between me and the intersection. There were cars exiting the freeway and turning through the intersection immediately in front of me. Fortunately, I had enough brakes to stop just before the intersection. I had my wife and son in the car. I will be having the local Ford dealership look over the car. That incident happened 5-10 minutes after leaving my house. I had used my brakes during this trip prior to the incident. The brakes worked normally for the remainder of the 20 minute trip. Whatever is going on, isn’t right and although I never was dangerously close to an accident, if conditions were slightly different it could have been very bad.

 

[Shayne]

I just had a similar experience about four hours ago during normal conditions (dry and daylight). I was approaching a red light that controlled an on/off ramp intersection where a rural road intersects a State Highway. I was on the rural road. Started braking and the pedal almost
immediately felt soft. I kept pressing (never pumped). The brake pedal travel more than double the distance that it normally does. I started to get some braking, but I don’t think I could have locked up the brakes if I wanted to. The emergency braking didn’t engage; however there wasn’t a car traveling in my lane between me and the intersection. The cars exiting the freeway and turning through the intersection immediately in front of me. Fortunately, I had enough brakes to stop just before the intersection. I had my wife and son in the car. I will be having the local Ford dealership look over the car. That incident happened 5-10 minutes after leaving my house. I had used my brakes. The brakes worked normally for the remainder of the 20 minute trip. Whatever is going on, isn’t right and although I never was dangerously close to an accident, if conditions were slightly different it could have been very bad.

Please report this experience to the nhtsa for the rest of us. That is the only way the HVJB got addressed.

 

[MNevan]

Please report this experience to the nhtsa for the rest of us. That is the only way the HVJB got addressed.

I’ll report it today.

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