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Discussion Starter · #1 ·
Hello everyone, been having a brake problem for the past week and can't seem to pinpoint the cause of it. Any help is appreciated!

When applying the brakes the pedal will just sink to the floor not stopping until about an inch away from its limit :sad:. As soon as I lift my foot up and reapply pressure, it travels to its normal point and stops as normal. This has happened at random times during the course of the week and I have not had any luck in recreating it. I did my brakes 2 months ago and their is still plenty of "meat" left on the pads, and the master cylinder is full of brake fluid. From the research I did, I saw that the breaks are vacuum assisted (Please correct me if I'm wrong) via a hose that connects on to the top of the engine. After verifying that it is secured correctly, i am stumped. Am i missing some sort of bleed valve?
Thanks,
Fixter
 

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Hello everyone, been having a brake problem for the past week and can't seem to pinpoint the cause of it. Any help is appreciated!

When applying the brakes the pedal will just sink to the floor not stopping until about an inch away from its limit :sad:. As soon as I lift my foot up and reapply pressure, it travels to its normal point and stops as normal. This has happened at random times during the course of the week and I have not had any luck in recreating it. I did my brakes 2 months ago and their is still plenty of "meat" left on the pads, and the master cylinder is full of brake fluid. From the research I did, I saw that the breaks are vacuum assisted (Please correct me if I'm wrong) via a hose that connects on to the top of the engine. After verifying that it is secured correctly, i am stumped. Am i missing some sort of bleed valve?
Thanks,
Fixter
The brake master cylinder may be full of brake fluid, but it doesn't mean that there isn't air in your lines. I suggest flushing your brakes and then reassessing. If that doesn't help, it is most likely your master cylinder that needs replacing.

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Discussion Starter · #3 ·
That's what i figured the next step would be. If their was air in the lines wouldn't the problem be more consistent? If i didn't have pressure at all i could see that, but the randomness of the situation has me thinking its something more complicated. Thanks for the reply!
 

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Master cylinder could have been damaged during the brake job, if the brake pedal was depressed all the way down right away. It causes excess travel in the master cylinder rod and damages the seal. after the pads get replaced I dont like to depress the brake pedal all the way to the floor all at once. I give it a couple taps at 50% travel a few times then slowly tap it all the way until I notice it gets firm and then depress it all the way down.

Like I said, I have seen it get damaged from brake jobs, but hopefully this is not your case, g/l
 

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Discussion Starter · #5 ·
Master cylinder could have been damaged during the brake job, if the brake pedal was depressed all the way down right away. It causes excess travel in the master cylinder rod and damages the seal. after the pads get replaced I dont like to depress the brake pedal all the way to the floor all at once. I give it a couple taps at 50% travel a few times then slowly tap it all the way until I notice it gets firm and then depress it all the way down.

Like I said, I have seen it get damaged from brake jobs, but hopefully this is not your case, g/l
Thank you guys for the replys, I'll re bleed the system and see if it will fix the problem, hopefully the master cylinder isn't damaged.


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A quick search I found a video explaining internal leakage of a mc. Hopefully your brake bleeding fixes it but I still beleive your issue is leaking seals in the mc.
 

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Have you double checked the clips on the Calipers?

A loose clip(Especially in the front) will cause this problem as well, since the caliper will not be able to properly grip the rotor.
 

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Discussion Starter · #8 ·
Does anyone know if the ECU has any influence on the vacuum assist system? Now that I’m thinking it began to start happening after I bumped my car up to the COBB Stage 2 tune


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Discussion Starter · #10 ·
^ NO will have no affect on the brakes, have you checked your front clips on the Calipers? Are they properly tight?
I did check those out as well, they seem like they are on there good, only way I’d be able to get them off is with pliers. I also re bled the system again last night(Still no air in the lines) . Didn’t have any problem on the way into work this morning, I’ll keep the thread updated if the problem persists. Thanks for the reply’s everyone, I do appreciate it!
 

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Hey MattB16teg how have your brakes been since bleeding? I just got mine back from the shop yesterday after having the back pads and rotors replaced under warranty (long ridiculous story there) noticed on the way home mine was doing the exact same thing. First contact with the pedal i get little braking pressure and it fades as if there is air in the line. let off the pedal and all of a sudden its normal, however mine is consistent and not random. I am going to bleed them tonight/tomorrow and see. The back pads were SHOT!! almost metal to metal on the back inside, and material was low enough to allow the the low brake fluid light to come on. Maybe it got low enough to get an air bubble in? hope its not the MC just because i don't like other people working on my car, and the MC would be replaced under warranty so i would have ford do it. Just let me know how yours has been
 

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From experience boiling brake fluid: If in doubt bleed thoroughly.

From experience - one of the dumber things I have done since I knew my pads were very thin: Getting down to metal to metal is bad, of course.
One of the reasons that metal to metal is bad is that the pistons come so far out that they can loose their seals, at least temporarily.
The failure may not be catastrophic, but if in doubt bleed.

I had braking issues that I concluded were probably in the master cylinder (MC).
I had rare foot to the floor no brakes. That particular season it was a couple of autocross events. Blow through some cones no problem.
I think it was internal leakage, and/or a vacuum leak. And the car had to be reliable before heading to a series of track events.

The dealer of course could not replicate the issue, and could not find a problem, and warranty was refused.
I talked to customer service, Ford Racing and Multimatic and none had useful suggestions for either diagnosis or improvements.
I had a race shop replace the MC on my dime, and the problem was solved.
Brakes have been good since then.
The MC was replaced when my 2013 ST was just over 2 years old, with a bit over 40k miles, and many track days and autocross had badly abused the brakes by then.
Tom Kennedy
facebook: TeamSparrow Speed
 
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