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Discussion Starter #1
Hi all,

I finally got in the game, having picked up a well-kept 2013 ST3 with 75k miles. These things sure are a blast to drive.

I caught something on the drive home that I failed to catch during my test drive. The brakes normally seem to bite really well and the pedal feel seems to be quite normal - not spongy or anything. The pads (OEM replacements) have about 40k miles on them, and the fluid was flushed about 20k miles ago. Nothing really stood out to me during my test drive.

On the way home my heart skipped a beat as a driver in front of me forced me to do a panic stop. The brake pedal immediately went hard as a rock and I had to put all of my weight into the pedal to get the car to stop. I then did some tests on empty roads and it doesn't appear to be related to braking while the clutch pedal is depressed; the firm pedal can occur when the clutch is either in or out. It really just seems to be when I firmly slam on the brakes.

Any obvious places to look for problems? I understand there's a vacuum pump to the right of the intake manifold and left of the air filter box, but no hoses connected to it appear to be loose.

Any advice is greatly appreciated.
 

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the vacuum pump is cam driven. it’s on the intake cam in front of the di pump.
 

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Discussion Starter #4
Hmmm I did some more testing and it doesn't appear to be due to being under boost. I was decelerating to a stop sign a good 5 seconds after boost and even though the pedal felt normal at first, it suddenly firmed up on me. Very strange.

Any ideas?
 

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Hmmm I did some more testing and it doesn't appear to be due to being under boost. I was decelerating to a stop sign a good 5 seconds after boost and even though the pedal felt normal at first, it suddenly firmed up on me. Very strange.

Any ideas?

I've had the same problem. I have drilled and slotted rotors all around with ceramic pads and at 120 mph I had minimal brakes after the initial bite. I'm suspecting brake fade due to heat. I'm waiting on some EBC yellowstuff pads.
 

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power brakes = brakes better while engine is at high RPMs... shift to N while coming to a stop and notice you will have "poor" braking feel. still brakes of course but you brake hard enough and can bog the engine a bit.

Then down shift and roll to a stop and notice that the braking is better and normal feeling to a stop as long as you shift down and keep RPMs "high" (not at idle)

just food for thought and to keep in mind.

Also the pedal feel you are describing can be "fixed" with enough money. "fixed" not 100% . stainless lines and better fluids can help with it.
 

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Discussion Starter #8
Does this fit what you are seeing? Or perhaps its not working as intended? Brake assist is supposed to aid in panic stop situations

https://owner.ford.com/how-tos/vehicle-features/brakes/brake-assist.html
Hmm interesting. I input my year and sync version and the website just gave me a video explaining brake assist. Not sure if my car has it, though.

Even so, it definitely doesn't feel like it's helping. Every time it happened I felt as though I was gonna plow into the car in front of me or right through that stop sign, instinctively reaching for the e-brake.
 

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Yeah, those hot spots arent a good sign...the '13s came with a more aggressive pad and smaller rotors, they changed them out in mid '14 for a different pad and slightly larger rotors. I would imagine the pads/rotors could wear a bit faster. Good news is brake jobs on this car are pretty straight forward and there are plenty of options. I would suggest an aftermarket pad, plenty of threads on what people prefer.

If you want a bit more rotor up front, the 12.6" to 13.1" is a decent upgrade (you lose ability to run 16" wheels though)
https://www.focusst.org/forum/focus-st-brakes/36021-12-6-13-1-upgrade.html

Or if you want an even larger setup, you can look at the RS Brembo's (350mm,) straight bolt on mod (you lose ability to run 17" wheels though)
https://www.focusst.org/forum/focus-st-brakes/97233-rs-brakes-install-tips-review-comparison.html

and since i am linking things, here is the franken brake link. Allows you to fit RS rear rotors(320mm vs 332mm using your existing rear calipers. You just need to source a caliper braket from a Mazda 5
https://www.focusst.org/forum/focus-st-brakes/34649-project-frankenbrake-larger-rear-brakes-budget.html
 

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Discussion Starter #12
Thanks for the great info/links. So you think that my weird firm pedal could merely be a matter pads/rotors?

It's funny you mention the 12.6 to 13.1" upgrade. I was aware of the larger rotors on the later models before I bought this, but I remember thinking that 12.6" is already sooo much bigger than my mustang gt's 10.5" front rotors. Then again, I used to think the 17" bullitt rims were HUGE. What a difference a decade makes :lol:
 

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Thanks for the great info/links. So you think that my weird firm pedal could merely be a matter pads/rotors?

It's funny you mention the 12.6 to 13.1" upgrade. I was aware of the larger rotors on the later models before I bought this, but I remember thinking that 12.6" is already sooo much bigger than my mustang gt's 10.5" front rotors. Then again, I used to think the 17" bullitt rims were HUGE. What a difference a decade makes :lol:
Thats not an issue i have seen before, so i dont want to just say yes that is absolutely your issue and then you throw money at the car and it doesnt fix it. Hot spots could be from cheaper rotors and whatever metal is mixed in causing the hot spots and it could just be from an aggressive pad. It can lead to uneven wear and vibrations but i cant say if that directly leads to your hard pedal and lack of braking power. A new set of pads/rotors and fresh fluid will surely help things and inspecting the various connections like the speed sensors/abs at each corner is a good idea too.

I went from the 12.6" up to the RS setup around the 30k mark and never looked back. Sure, the 13.1's and a good pad would have been adequate but i figured do the brakes once and they have been good to me since (i'm a sucker for a big caliper up front.) I also have way more power than stock, so i wanted the brakes to keep up. Every setup has its pros and cons, so you just need to decide what works good for you. If not do spirited driving that sees heavy brake use, the 12.6's are fine. If you want a bit more rotor, go up to the 13.1's.
 

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It seems like an easy cheap way to test would be to put a vacuum gauge like this tee'd into your brake booster hose and then with the car idling slam on the brakes and see if the vacuum changes. The brakes don't know if your car is moving or not so you don't need to be moving to test (unless your anti-lock system is playing a part in the issue). I'd expect a slight blip maybe but for it to hold full vacuum within a fraction of a second.

My guess based on your symptoms is that your booster itself is bad and is leaking air in faster than the vacuum can pull it but only leaking when the brake pedal is depressed.

I highly doubt your pads or rotors or calipers have anything to do with this problem as they wouldn't make your pedal suddenly get harder.
 

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It seems like an easy cheap way to test would be to put a vacuum gauge like this tee'd into your brake booster hose and then with the car idling slam on the brakes and see if the vacuum changes. The brakes don't know if your car is moving or not so you don't need to be moving to test (unless your anti-lock system is playing a part in the issue). I'd expect a slight blip maybe but for it to hold full vacuum within a fraction of a second.

My guess based on your symptoms is that your booster itself is bad and is leaking air in faster than the vacuum can pull it but only leaking when the brake pedal is depressed.

I highly doubt your pads or rotors or calipers have anything to do with this problem as they wouldn't make your pedal suddenly get harder.
I doubt the brake booster is bad. These cars don't have a vacuum pump on the brake boost. So when you go from boost to brakes the system doesn't have time to grab enough vacuum to assist the brake booster. Now if you go from boost to vacuum for a second or two then brakes you should notice an assisted brake feeling vs a hard pedal.

Sent from another garage.
 

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I doubt the brake booster is bad. These cars don't have a vacuum pump on the brake boost. So when you go from boost to brakes the system doesn't have time to grab enough vacuum to assist the brake booster. Now if you go from boost to vacuum for a second or two then brakes you should notice an assisted brake feeling vs a hard pedal.

Sent from another garage.
The booster has a check valve and stored vacuum so the boost doesn't affect the brakes unless you were to repeatedly pump the brakes while maintaining boost. He said his pedal is easy to push at first and then gets hard so it sounds like he has vacuum when first pressing the pedal and then is losing vacuum despite the engine idling and theoretically providing more vacuum. So something must be letting air in but only when the pedal is pressed, and the booster is what makes the most sense to do that.
 

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Years ago I had the same issue as the OP, loosing brake boost.
I think I commented on it specifically in one or more threads, and have commented in many other threads on brakes in general.
My car, also a 2013, for the first several years saw many autocross days and many track days. Now it occasionally gets a track day.
My brakes have been badly abused and overheated. Boiled fluid, heat cracked several sets of rotors, all consumables, no problem. Great brakes, with pads, fluid and ducts.
Back to OP's issue. In autocross essentially no breaks, completely blew a couple of turns, but inconsistent.
I concluded loss of brake boost.
Lack of brake boost, nobody could duplicate the issue. I talked to a couple of dealers, Ford Racing, Octane Academy techs, Mountune. No help no suggestions. I was asking for a better master cylinder, or more vacuum, or known issues.
Maybe somebody agreed with my conclusion that there might be a vacuum leak in the master cylinder. Dealer denied any support.
Lacking any better ideas, I had a good independent shop replace the master cylinder with a new OEM one.
That solved the problem.
facebook: TeamSparrowSpeed
 

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Discussion Starter #18
I'm thinking that this has nothing to do with boost to brake. Earlier today, I was driving around the neighborhood and hitting no boost. Coming to a stop sign downhill from 20mph, the brake pedal started normally and firmed up on me, almost making me run clear through the stop sign.

Something's definitely not right.
 

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Discussion Starter #19
I just tried the standard brake booster test and it passed - With the car off, I pumped the brake pedal until it firmed up and, while keeping moderate pressure on it, turned on the car. I did feel the pedal move forward as the engine fired up, indicating a functioning brake booster.

I also checked the brake fluid level - it's perfectly at the middle mark. Fluid was flushed 15k miles ago, so I assume if fluid was leaking through the seal in the MC, it would be low by now, no?
 

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Discussion Starter #20 (Edited)
Ok so I pulled off the wheels today with the intention of pulling the pads, only to run into those hex bolts holding the slide pins. In spite of my well-equipped garage, I did not have a stubby hex key or shallow hex socket, so I wasn't able to pull the pads off. I did take a close look at them and it looks like the fronts are paper thin:

IMG_8073.jpeg
IMG_8069.jpeg

The rears seem to have a little bit of meat on them, as you can still slightly see the beveled edge showing. Tough to tell without pulling them off, but I doubt the rears have anything to do with this pedal firming:

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IMG_8063.jpg

One thing I've never seen before - the outer edges of the rotors are raised in comparison to the rest of the surface in which the pad makes contact. This is especially pronounced in the front rotors:

IMG_8071.jpeg
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What does this mean? Were they cut in the past and the knife just never made it to the very edge? I've actually used a lathe before (family member owns one) and I can't see how that would happen. Can the pads cut into the rotor like this?

Would the super thin pads be a possible cause for the suddenly firm pedal?

I also bled the brakes while I was at it. No obvious air in the system.

Advice is deeply appreciated.
 
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