Brake Failure - Christmas Tree and Check Brake System

[KABQ]

First, I've done some searching and others have had similar issues, but in very different contexts. The vacuum line is a known issue on the 2.3, and removing the doors with the car on also causes a freakout. This is a 2.7 with the doors fitted.

Today I got caught in some construction and had to sit for about 5 minutes. A.S.S was on, so the engine was not running. After about 4 minutes I got a ton of error warnings (Service AdvancTrac, Check Brake System, Hill Start Assist Not Available, and Pre-Collision Assist Not Available) and the brake pedal vibrated several times then lost pressure. Since I was stuck in a one lane construction zone, I basically had to keep driving for several miles (at a HUGE distance from the car ahead of me) before I could pull over. When I could finally get it off the road and onto the shoulder, I had no pedal pressure and had to use almost the full pedal travel before the brakes engaged. When they eventually bit, it was full lock up. I shut it off for roughly 2 minutes, it made whole bunch of whirs and clunks, and was fine when I restarted it but the brake light on the dash was still on. When I tried to gently pull forward to test things out, it displayed that the parking brake turned off and the brake light went out. I had no problems for the rest of the drive and haven't been able to reproduce it. I'll call my dealer tomorrow, but I have a feeling they'll say "we can't reproduce the problem" and send me on my way. Any advice is greatly appreciated.

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[mj63]

Diagnostic trouble codes should be stored, if you get a good tech they might be able to figure out what caused the cascading failure.

 

[DesertRunner]

I have a similar issue with loosing power assist on the brakes (I had to push very hard to keep the vehicle from moving) but it would only happen intermittently on startup and usually after the vehicle had been sitting. Restarting the car would clear the errors and behavior. I took it to the dealer and they reflashed the abs unit, there is a tsb, but it still has the issue, only now it won't throw the error msg. It's back at the dealer but I'm not optimistic.

 

[Ford Motor Company]

First, I've done some searching and others have had similar issues, but in very different contexts. The vacuum line is a known issue on the 2.3, and removing the doors with the car on also causes a freakout. This is a 2.7 with the doors fitted.

Today I got caught in some construction and had to sit for about 5 minutes. A.S.S was on, so the engine was not running. After about 4 minutes I got a ton of error warnings (Service AdvancTrac, Check Brake System, Hill Start Assist Not Available, and Pre-Collision Assist Not Available) and the brake pedal vibrated several times then lost pressure. Since I was stuck in a one lane construction zone, I basically had to keep driving for several miles (at a HUGE distance from the car ahead of me) before I could pull over. When I could finally get it off the road and onto the shoulder, I had no pedal pressure and had to use almost the full pedal travel before the brakes engaged. When they eventually bit, it was full lock up. I shut it off for roughly 2 minutes, it made whole bunch of whirs and clunks, and was fine when I restarted it but the brake light on the dash was still on. When I tried to gently pull forward to test things out, it displayed that the parking brake turned off and the brake light went out. I had no problems for the rest of the drive and haven't been able to reproduce it. I'll call my dealer tomorrow, but I have a feeling they'll say "we can't reproduce the problem" and send me on my way. Any advice is greatly appreciated.

Hello there. Can you send over a message with your VIN and the name/location of the dealership you are reaching out to? I would like to take a closer look at your Bronco's brakes and error messages.

 

[rtazz17]

I would hope ford would not say we cant reproduce it. Not in this case at least..I would be afraid to put my family in that vehicle again or possibly hurt others on the road.

 

[KABQ]

Diagnostic trouble codes should be stored, if you get a good tech they might be able to figure out what caused the cascading failure.

I agree that it was a cascading failure starting with the braking system since all the other systems rely on the brakes to operate. This makes me think the problem started as a glitch in one module, then was detected by the others.

 

[mj63]

I agree that it was a cascading failure starting with the braking system since all the other systems rely on the brakes to operate. This makes me think the problem started as a glitch in one module, then was detected by the others.

All of those functions/features are within the ABS module. If the service department techs are able to pull snapshot data along with each DTC, there might be enough info to figure out which happened first and why.

What you felt was what is called "fallback" braking - basically you have to push through the pedal feel simulator in order to manually actuate the physical master cylinder (it is normally actuated by an electric motor & ball screw assembly in the 2.7l electronic brake boost vehicles). It doesn't feel good, but does meet all FMVSS requirements for minimum deceleration rates at the vehicle's max gross vehicle weight rating with failed boost.

 

[KABQ]

All of those functions/features are within the ABS module. If the service department techs are able to pull snapshot data along with each DTC, there might be enough info to figure out which happened first and why.

What you felt was what is called "fallback" braking - basically you have to push through the pedal feel simulator in order to manually actuate the physical master cylinder (it is normally actuated by an electric motor & ball screw assembly in the 2.7l electronic brake boost vehicles). It doesn't feel good, but does meet all FMVSS requirements for minimum deceleration rates at the vehicle's max gross vehicle weight rating with failed boost.

Thank you. That's exactly what I was feeling. The more information I'm armed with at the dealer the better.

 

[Jazer]

When you say ASS was engaged and the vehicle wasn't running, was it off the full 5ish minutes you were in traffic? If so that might be the start of the problem. Mine never stays off for more than a minute or so at a time, regardless of parameters.

 

[KABQ]

When you say ASS was engaged and the vehicle wasn't running, was it off the full 5ish minutes you were in traffic? If so that might be the start of the problem. Mine never stays off for more than a minute or so at a time, regardless of parameters.

I've trained myself to ignore the ASS so I don't recall if it stayed off the entire time, but the engine was definitely not running when the problem occured.

 

[Snacktime]

How many miles? Check you grounds?

 

[KABQ]

How many miles? Check you grounds?

About 1300 miles when it happened. I'll check the fuse box grounds and batt cables when I get home, but it hasn't done anything else weird and voltage is normal.

 

[Jazer]

How many miles? Check you grounds?

About 1300 miles when it happened. I'll check the fuse box grounds and batt cables when I get home, but it hasn't done anything else weird and voltage is normal.

This was my next suggestion. Check your fuse box bolts, battery terminals & grounds. On more than a few occasions this caused weird issues for people, usually at an intersection/stop. It's at least an easy thing to cancel out/start with.

 

[KABQ]

This was my next suggestion. Check your grounds, battery terminals & grounds. On more than a few occasions this caused weird issues for people, usually at an intersection/stop. It's at least an easy thing to cancel out/start with.

My hope is for something simple and obvious like that. Basically anything to keep it out of the dealership.

 

[Jazer]

My hope is for something simple and obvious like that. Basically anything to keep it out of the dealership.

I corrected my post, I meant to say "fuse box bolts, battery terminals & grounds". Good luck!

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