Weird Brake issue I need help solving

[TurboTim]

I have a brake issue and I don’t know what to do next to solve this.
I hope this forum can help.

What is the problem:

• The front driver side brake seems not to be working.
• When I break soft or hard, the car steers to the right without any steering input.
• There is no noticeable difference in feel at the brake pedal
• The driver side brake disc is cold, while the other three are all warm/hot, after a bit of driving/braking.

What have I done so far:

• I tried to brake more often and hard to maybe get it going again on its own.
• I have removed both front calipers, cleaned them as good as I can, pushed the pistons back and forth a few times and lubed everything that needs to be lubed.
• Changed brake pads while I was at it. The discs still looked good.
• The pistons in both calipers move when I press the brake pedal.
• I don’t think I lost brake fluid, just looking at the reservoir.
• The flexible brake lines still look good from the outside. Nothing obvious.
• I re-calibrated the ABS with ForScan.
• Checked for codes with my Accessport and with ForScan.

What should I try next ? :

• I don’t think it would be a failed wheel speed sensor, because I would get a fault code. Or wouldn’t I ?
• If it is the ABS module, I should see the fault code as well. Or not ?
• I could bleed the system, but I don’t think there is a reasonable explanation that there is one air bubble all the sudden in just one brake line.
• The only idea I have is to swap the flexible brake lines for new ones and maybe get a “repair”-kit (a bunch of seals) for the brake caliper. But I don't have much hope that this solves it.
• Anything else ?

Or is this a known issue of our Fiestas with a known (easy) fix, I’m just not aware about ?

Thanks

 

[Dialcaliper]

Next step. I’d check the rear calipers, especially the sliding pins for sticking and/or excessive pad/rotor wear (check both inner and outer pads). A sticky rear caliper/slider pins can yaw the car and feel like you would imagine the issue being in the front brakes.

Doesn’t sound immediately like an air or hydraulic issue as you’d be feeling sponginess in the brake pedal, but with one possible exception. Get ahold of a copy of Forscan and run through the brake diagnostics and bleed cycles as there’s a very small chance a valve in the ABS unit is sticking.

 

[TyphoonFiST]

Look for kinking in a hard brake line* the smallest kink can cause an issue in applying pressure evenly to the braking system.

 

[TurboTim]

Thanks for the answers so far.

Next step. I’d check the rear calipers, especially the sliding pins for sticking and/or excessive pad/rotor wear (check both inner and outer pads). A sticky rear caliper/slider pins can yaw the car and feel like you would imagine the issue being in the front brakes.

Doesn’t sound immediately like an air or hydraulic issue as you’d be feeling sponginess in the brake pedal, but with one possible exception. Get ahold of a copy of Forscan and run through the brake diagnostics and bleed cycles as there’s a very small chance a valve in the ABS unit is sticking.

Because the other three brake discs are warm after driving/braking, I'm assuming they all work, except the front driver side, which is cold.

I already used Forscan to re-calibrate the ABS. Is that what you meant or is there another function, apart from bleeding ?

Look for kinking in a hard brake line* the smallest kink can cause an issue in applying pressure evenly to the braking system.

This sounds like another possible cause to me, but how would a kink like that even emerge ?

I'm gonna be honest, I don't even know where the hard lines are located. I'll have to look this evening. Do they go from the wheel well behind the engine and then up to to ABS pump ?

 

[Dialcaliper]

Thanks for the answers so far.



Because the other three brake discs are warm after driving/braking, I'm assuming they all work, except the front driver side, which is cold.

I already used Forscan to re-calibrate the ABS. Is that what you meant or is there another function, apart from bleeding ?



This sounds like another possible cause to me, but how would a kink like that even emerge ?

I'm gonna be honest, I don't even know where the hard lines are located. I'll have to look this evening. Do they go from the wheel well behind the engine and then up to to ABS pump ?

That’s useful to hear - specifically I’m talking about bleeding that corner (or all 4) using Forscan to trigger the ABS unit to pump fluid into a bleeder bottle.

 

[TyphoonFiST]

Thanks for the answers so far.



Because the other three brake discs are warm after driving/braking, I'm assuming they all work, except the front driver side, which is cold.

I already used Forscan to re-calibrate the ABS. Is that what you meant or is there another function, apart from bleeding ?



This sounds like another possible cause to me, but how would a kink like that even emerge ?

I'm gonna be honest, I don't even know where the hard lines are located. I'll have to look this evening. Do they go from the wheel well behind the engine and then up to to ABS pump ?

Accident* Previous work completed. Road debris. I'd check the Hard lines at the front to both sides from the Brake caliper hoses.

 

[TurboTim]

Just to close / solve my own questions... Maybe it will help someone in the future.

I tried to reset the whole ABS unit in Forescan
I cleaned and lubed all the sliding surfaces on the calipers.
I changed the seals inside the calipers.
I replaced all brake lines
I checked the hard lines while I was at it and blew tons of brake fluid and compressed air through it.
I obviously bleed the system.
...

None of the above helped me with my problem.

So I removed the whole ABS block and asked Ford how much it was to replace it. But after I heard the price they wanted me to charge for that, I went a different route and send it to a ECU/ABS repair service. After they did some magic to it, everything works again as it should be and my car brakes on all 4 corners again.

I don't know what exactly they did to the ABS block, but I'm assuming it was a stuck valve or something similar.