No brake pressure after track sessions.

[Questionable]

So you had the issue on stock brake setup, then your still having the issue with the new V-Maxx big brake kit. Have you contacted that vendor to see what they say? Have you done temp paint to see how hot you are getting calipers and rotors?
https://alconkits.com/support/install-tips/99-using-brake-temperature-paint

The stock MC wasn't designed to take the loads you are putting on it, adapting a Wilwood could be the next approach. Or an ice mode, but can't you pull the ABS fuse to remove that from system?

I have some of the Alcon caliper temperature stickers, and I should try them on the V-Maxx calipers just to see how they compare. But I think you're right with the idea that I'm overtaxing something upstream from the calipers. Either the master cylinder or the ABS module/programming (I'm still thinking it's electrical since I've "fixed" the issue before with sensors).

I think the ST200's from the other side of the pond have a uprated master cylinder. @ron@whoosh was gonna look into it but I don't know if he ever got a chance.

Now that's interesting. I'll see if I can find anything about that, because I'm curious if anything else is different.


As an aside, does anybody know if we have actual pressure sensors reading what the master cylinder is doing or did Ford decide that switches attached to the pedal was enough to determine the driver's intention? I'm reading up on the Mk60 standalone ABS kits available and they use pressure sensors on the MC in addition to wheel speed sensors.

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[kevinatfms]

I have some of the Alcon caliper temperature stickers, and I should try them on the V-Maxx calipers just to see how they compare. But I think you're right with the idea that I'm overtaxing something upstream from the calipers. Either the master cylinder or the ABS module/programming (I'm still thinking it's electrical since I've "fixed" the issue before with sensors).
Now that's interesting. I'll see if I can find anything about that, because I'm curious if anything else is different.
As an aside, does anybody know if we have actual pressure sensors reading what the master cylinder is doing or did Ford decide that switches attached to the pedal was enough to determine the driver's intention? I'm reading up on the Mk60 standalone ABS kits available and they use pressure sensors on the MC in addition to wheel speed sensors.

Have you tried running a track day with the ABS fuse pulled? From the sound of it the Torque Vectoring is your issue.

Also, an LSD would work wonders to reduce the intrusion of the Torque Vectoring.

 

[Woods247]

Are you activating ABS? I wonder if you have air in the ABS module.

 

[Questionable]

Have you tried running a track day with the ABS fuse pulled?

I haven't. I would rather have the ABS than pull the fuse and maybe have the computer freak out on track. That was something to try before, but now I'm just mad at the whole system.

[ ... ] From the sound of it the Torque Vectoring is your issue.

Also, an LSD would work wonders to reduce the intrusion of the Torque Vectoring.

I've had an LSD for two years. It did help.

Are you activating ABS? I wonder if you have air in the ABS module.

That has occurred to me. I wasn't hammering ABS, but I did activate it at the end of the front and back straights.

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[Questionable]

Update! I fixed the problem! Again!

By replacing the cruise control switch.
Again.


After the last event, I got my car to the shop that's been prepping/repairing my car. They bled the system, bled the ABS, and added check valves to the calipers (~2PSI to keep the pads from knocking back supposedly). That helped, but didn't fix the problem. They also pulled codes and got "C0040:64-68/CMDTCs Brake pedal switch A".

So I ordered a new Brake Pedal Switch A (the blue/cruise control switch). It arrived today and I installed it. And after removing the vacuum bleed-off setup my brakes are back to normal.


I should have read my own thread before doing anything and ordered another switch. I have *2 more* fresh switches ordered just to keep on hand with camshaft and crankshaft sensors at the track. Because this time I'll learn.


To any future Fiesta drivers trying to solve this issue: SWAP THE BLUE SWITCH ON THE PEDAL FIRST. IT'S $5 AND TAKES 5 MINUTES.

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[Intuit]

For matters of safety, brakes are supposed to be among the most simplistic of systems on the vehicle. Anything approaching this level of stupidity just proves that technology in the braking system has gotten out of hand and become too technical.

Is there such a thing as a legal ABS delete? (legal means you won't have dash lights and computer codes)

 

[Ford ST]

For matters of safety, brakes are supposed to be among the most simplistic of systems on the vehicle. Anything approaching this level of stupidity just proves that technology in the braking system has gotten out of hand and become too technical.

Is there such a thing as a legal ABS delete? (legal means you won't have dash lights and computer codes)

Absolutely agree. What's sad many vehicles today have brake by wire no mechanical linkage at all. That's just plain nuts.

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[TaylorGoesFast]

Update! I fixed the problem! Again!

By replacing the cruise control switch.
Again.


After the last event, I got my car to the shop that's been prepping/repairing my car. They bled the system, bled the ABS, and added check valves to the calipers (~2PSI to keep the pads from knocking back supposedly). That helped, but didn't fix the problem. They also pulled codes and got "C0040:64-68/CMDTCs Brake pedal switch A".

So I ordered a new Brake Pedal Switch A (the blue/cruise control switch). It arrived today and I installed it. And after removing the vacuum bleed-off setup my brakes are back to normal.


I should have read my own thread before doing anything and ordered another switch. I have *2 more* fresh switches ordered just to keep on hand with camshaft and crankshaft sensors at the track. Because this time I'll learn.


To any future Fiesta drivers trying to solve this issue: SWAP THE BLUE SWITCH ON THE PEDAL FIRST. IT'S $5 AND TAKES 5 MINUTES.

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I wish I had read this thread 2 days ago. Shut down my whole track weekend because I thought I had a faulty master cylinder. I'll try replacing these switches and see if it fixes things. Do you have a part number?

 

[Questionable]

I wish I had read this thread 2 days ago. Shut down my whole track weekend because I thought I had a faulty master cylinder. I'll try replacing these switches and see if it fixes things. Do you have a part number?

Surprisingly, I don't have any switches on hand. I recently retired my Fiesta from track duty and got a Miata to take over as the "racecar." But I do have a RockAuto link for you:
MOTORCRAFT SW7020 (alternative P/N: AA6Z9C888A)

EDIT: Buy a couple, and take them with you to the track. They're easy to replace, you don't have to remove the airbag for access (unlike the black switch). I have given them to other Fiesta drivers when they had the same issue because I'll eat $5 to save someone's track day.

 

[Intuit]

Have you been able to ascertain a reason for... not just failure... but repeated failure?

 

[Questionable]

No. Maybe the switches are just not up for the harsh abuse I put the brake pedal through (I am/was particularly hard on my brakes and bled them almost monthly for a couple years before I switched to Castrol SRF), but maybe it's something else. I didn't have the time or resources to really figure out what was actually broken in the system, just how to keep it going since it was my only car. Now that I have a second car that's better suited for track duty, I won't track the Fiesta again unless I strip and cage it, at which point I'll ditch the stock ABS.

It would have been interesting if I figured out a way to make the B-Spec ABS module I have work in my car, to see if it's the entire computer system or just the switch, but that was also beyond my time and resources.

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[TaylorGoesFast]

So, I replaced the switch and it did not help. Bled the brakes again, did not help. Replaced the master cylinder, did not help. Bled the brakes with the car on, all 4 tires in the air, and it still did not help. At this point I'm figuring I'll take it to a dealership or some shop that can do all 4 at once and actuate the ABS. Am I missing something?

The pedal started acting this way as soon as I changed the brake pads. I've changed pads a million times across tons of cars, and I checked my work again today, so I don't think I did anything wrong. Not sure what's going on. I'm figuring it has to be air in the ABS pump. Frustrating... and all because I wanted to not skip a track weekend while my other car was getting a cage....

 

[johnny5]

Stupid question, have you checked the rear pads? We had a similar issue after a pad change, and we found the nub on the pad wasn't going into one of the cut outs in the piston. This caused the pedal to feel like it wasn't building pressure.