Loss of Brakes

[lolder]

I guess you'll have to replace the assembly.

[savngas]

Update

2000 miles (summer vacation trip) since 12v battery replacement and all is well.

Still make you wonder....

Harry

[lolder]

Update

2000 miles (summer vacation trip) since 12v battery replacement and all is well.

Still make you wonder....

Harry

Great! Good luck. The brake pedal assembly ( called a simulator,

I think ), is mainly a variable resistor and a spring and should be reliable. The computer that co-ordinates the re-gen and mechanical brakes and traction control and ABS is the heart of everything.

In the event of a computer failure, the brake pedal arm travels over an inch further down into a "U" shaped fork and physically contacts the mechanical brake master cylinder and applies the power mechanical brakes. You can get under the instrument panel and watch this as you press on the brake pedal with the car on or off. When everything is working correctly, the U fork travels just ahead of the pedal arm as there is an electrical actuator in the brake master cylinder.

[BKFusionHybrid]

When it seems you lost the brakes, mechanical brakes are still functional, just have to press on the pedal harder.

In my case I had to replace ABS module and it was fine after.

Edited November 26, 2016 by BKFusionHybrid

[bradhoy]

I had the same issue with my 2011 Fusion Hybrid...ABS, Advance Trac, brake lights came on and brake pedal went to the floor after a 3 point turn at 75,000 miles and many months of limited use due to COVID.  I replaced the ABS module, bleed the brakes after putting brake system in maintenance mode, then ran multi-Calibration and Regen Cal all using Autophix 7710.  To gain access to the ABS module I removed the plastic cover (cowling?) on top of the engine, removed the two nylon/plastic ball headed attachments that had retained the rear of the cowling allowing the AC line to be moved out of the way.  There is also a firewall mounted item on the far left side (viewing from the front of the vehicle) that was unbolted and pushed to the side to gain access.  I removed the ABS module (passenger side against firewall) leaving the mounting bracket in place.  I disconnected the hydraulic lines on the top and side of the ABS module using a 13mm flare nut wrench after removal of fluid from the brake reservoir. Have a rag handy to absorb any residual fluid when loosening the flare nuts. At this point remove the HCU connector by squeezing the lower part of the retainer and pulling up 90 degrees to release.  After this I backed out the rear bracket mounting bolt using an 18mm ratcheting stubby wrench reaching behind the unit....in the blind.  This bolt has a very thin head in a tight space that required the stubby to fully engage.  Once this bolt is fully backed out I used a 15mm standard stubby wrench to back out the two attachments from the ABS module on the base.  All 3 attachments go through rubber bushings that retain them after disengagement. At this point the ABS module and HCU attached to the rear of the module was easily removed.  Next step is removing the 4 screws holding the HCU on back of the ABS module.  Clean and inspect the HCU before mounting on the new ABS module.  Install unit in reverse order.  I used a power bleeder to bleed the brakes once in maintenance mode.  If the brakes are still spongy, bleed more.  When all wheels have been bleed and brakes hard you are ready to run the calibrations routines. Good Luck!!

[md40022]

So I am dealing with something possibly similar within the last week. Here is my scenario....

 

2010 FFH 118k

 

On Wednesday 8/18 I got a "check brake fluid" message on the dash. And sure enough the reservoir was virtually empty when I checked, the brakes felt fine though. Pressure felt okay and not making any noises. . I stopped off at the gas station and filled it up with Dot3 fluid and message immediately went away.

 

Checked brake fluid level on Sunday 8/22 just to see if any change from when I filled it up a few days ago. The reservoir was maybe a half-inch lower than where it was when I filled it up before. My assumption was that there's a leak somewhere, hence why I was low in the first place. I topped it off that extra half inch and was planning to take it in for service as soon as I was able to

 

Now today (Tuesday 8/24) I just got numerous lights popping up on the dash all at the same time.... "Check Brake System",, "Service AdvanceTrac",, "ABS",, "the little stability control swerving car icon, and the "BRAKE" icon that you get when you put the emergency brake on. These all popped up at the same time, but oddly enough the original "check brake fluid" message did NOT pop up. When I check the fluid, it is once again about a half-inch lower than where it was when I topped it off, but by no means is it low - at least not yet. Brake pressure feels fine still. Brakes not making any noises.

 

So my assumption is, I got a leak somewhere in the brake system and I will address that. But I'm worried about all these other messages that have since popped up. Initially I thought maybe some air got in the system when I topped the fluid off and now the computer is acting wacky and I need to bleed the air out?  But the 12 volt battery thing that was mentioned earlier in this thread and seemed to solve the original poster's problem is making me think now...... I did have the car sitting in "park" with the A/C blasting for about 30 minutes while I was on an important phone call earlier today. It was going back and forth between EV and 12volt several times over those 30 minutes. I would have thought the alternator would be keeping the 12v charged during this time (the ignition was fully on), and my god would it be awful coincidence that the battery would be the cause of this just a few days after the brake fluid being very low, but given all of the circumstances - now I'm really curious.

 

Opinions??

 

** UPDATE** - Just tested the 12v battery with a multi meter. Car had been sitting for only about an hour and a half though. 12.4 volts with the engine off, 13.6 with the engine on. Those voltages seeeeeem okay, but since it was only sitting for an hour and a half I suppose that 12.4 could be lower if I tested it after letting it sit overnight..... Also, no trouble lights came on the dash at all when I tested, though I only let it run for a few minutes so maybe they would have come on if I gave it more time. I'm really wondering if this is a 12volt battery issue given the similarities to the original post. But MY GODDDD would that be freakish luck given that I just noticed a probably leak in the brake lines a few days prior.

Edited August 24, 2021 by md40022
Adding more info

[akirby]

Could be the battery but it’s more likely the leak messed up a wheel sensor or it’s in the ABS system.

[md40022]

Got it at the shop right now. They are saying a leak at the rear calipers - so they are doing the rear pads, calipers and rotors for me now.

 

I am also replacing the 12v battery just because I know it's probably about that time (measured at 12.1 vdc this morning after sitting overnight) - whether that factored in to my situation or not, who knows.

 

Hopefully their diagnosis is accurate. I guess we'll know more within the next day or two.

[akirby]

Make sure they test/check the sensor and tone ring - may be damaged.

 

As for the battery if it’s more than 3 yrs old just replace it.  But you can’t go by voltage.  Get a SOLAR digital tester that measures CCAs.

Edited August 25, 2021 by akirby

[drolds1]

Quote

I would have thought the alternator would be keeping the 12v charged during this time (the ignition was fully on),

Just an FYI: the Hybrid doesn't have an alternator, per se.  The 12V battery is charged by the HVB using a DC to DC converter to drop the voltage down to around 14 VDC.