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Friend having a brake problems at the track

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Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Hi everyone, my friend has a 2013 Mustang GT with the Stoptech ST60 brakes, Pagid pads, Koni yellows, P springs, BBK headers, Accufab TB, no cats, Hoosiers, etc.

The funny thing is he is doing very well in the local circuits even though its automatic.... He does have a big problem that after the first big use of brakes, his peddle goes hard and he loses brakes, after a a few seconds it comes back to normal, usually once he gives it a little throttle. With the manual in my Boss I have never had anything similar happen to me.

Any Ideas what it could be??
 

TMSBOSS

Spending my pension on car parts and track fees.
7,530
5,247
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
Mad Hatter said:
Hi everyone, my friend has a 2013 Mustang GT with the Stoptech ST60 brakes, Pagid pads, Koni yellows, P springs, BBK headers, Accufab TB, no cats, Hoosiers, etc.

The funny thing is he is doing very well in the local circuits even though its automatic.... He does have a big problem that after the first big use of brakes, his peddle goes hard and he loses brakes, after a a few seconds it comes back to normal, usually once he gives it a little throttle. With the manual in my Boss I have never had anything similar happen to me.

Any Ideas what it could be??
re

Hard pedal which improves with throttle??


Sounds like the problem is related to the brake vacuum booster.

I would check vacuum leaks first.

First I have heard of this.

Good luck.
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
Any chance he has an oil catch-can installed, specifically a JLT? If so make sure he doesn't have the version with plastic fittings that were known to crack and cause vacuum leaks.

NEXT point of inspection is at the power brake booster vacuum line itself; the guys from Vorshlag had an issue with these on their GT a couple years back. Cheap fix.

http://www.vorshlag.com/forums/showpost.php?p=57301&postcount=173

Part # 15 here: http://parts.autonationfordwhitebearlake.com/auto-parts/2013/ford/mustang/gt-trim/5-0l-v8-gas-engine/brake-cat/brake-hydraulics-scat/jc104405-assy
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
ArizonaBOSS said:
Any chance he has an oil catch-can installed, specifically a JLT? If so make sure he doesn't have the version with plastic fittings that were known to crack and cause vacuum leaks.

NEXT point of inspection is at the power brake booster vacuum line itself; the guys from Vorshlag had an issue with these on their GT a couple years back. Cheap fix.

http://www.vorshlag.com/forums/showpost.php?p=57301&postcount=173

Part # 15 here: http://parts.autonationfordwhitebearlake.com/auto-parts/2013/ford/mustang/gt-trim/5-0l-v8-gas-engine/brake-cat/brake-hydraulics-scat/jc104405-assy

Great tip. We will check it out right away!

Sent from my GT-I9100 using Tapatalk 2
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Found the problem!! His GT is without the Brembo package, which is why he got the ST60 Stoptech brakes. So he needs to get the GT500 power brake booster to compensate!

The video from latemodelrestoration explains it!

https://www.youtube.com/watch?v=ld_e2MCuNPU
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
I'm honestly not convinced that is the problem; we put ST60s on a 2006 Mustang GT-turned-race-car (Brembos weren't an option then, and the GT500 didn't exist yet), and we never had an issue with the brakes like you described. (Edit: We actually did ST60s on three separate '06-07 Mustang GTs that got turned into race cars and none of the cars had any sort of braking issues with the factory booster.)

Moreover I added the factory Brembo kit to my own 2006 GT without changing the booster and without any noticeable change in pedal modulation or feel.

Try changing out that vacuum fitting I mentioned before you sink a bunch of cash and time into that booster.
 

TMSBOSS

Spending my pension on car parts and track fees.
7,530
5,247
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
ArizonaBOSS said:
I'm honestly not convinced that is the problem; we put ST60s on a 2006 Mustang GT-turned-race-car (Brembos weren't an option then, and the GT500 didn't exist yet), and we never had an issue with the brakes like you described. (Edit: We actually did ST60s on three separate '06-07 Mustang GTs that got turned into race cars and none of the cars had any sort of braking issues with the factory booster.)

Moreover I added the factory Brembo kit to my own 2006 GT without changing the booster and without any noticeable change in pedal modulation or feel.

Try changing out that vacuum fitting I mentioned before you sink a bunch of cash and time into that booster.

+1

Try locating potential vacuum leaks first.

Will only take an hour or so and will eliminate the cheap fixes first.

You can always order the booster if you can't find a leak.
 
We've installed the 14" Brembo front brakes both on 2011+ base models and on earlier cars. We have not had an issue with any of the boosters and pedal feel or throw.

As mentioned earlier, we have had issues with both the booster check valves (twice) and with the plastic fittings in the JLT breather can. We replaced the check valve twice, and the second one seems to be good as we have not had any other issues with it. We replaced the JLT fittings with brass parts, and built a bracket so it wasn't hanging on the lines. Then later replaced the entire system that captured oil from both banks.

The original plastic fittings
IMG_3140-M.jpg

DSC1532-M.jpg


The replacement fittings
DSC1617-M.jpg


The replacement system using the Moroso can
_DSC1603-M.jpg

_DSC1639-M.jpg
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Great Stuff, I have him convinced to try the check valve right away. He already purchased the GT500 brake booster and the JLT oil can to install next week, so you your comments are very welcome!!
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
4,008
1,924
Exp. Type
W2W Racing
Exp. Level
10-20 Years
Cookeville TN
blacksheep-1 said:
As I recall Ford makes a specific competition brake booster that we use on our cars.

Yes $3500 booster and master cylinder combo built by TRW. Can't see buying this for a hobby track car but some have. I replaced mine with the 2013 GT 500 booster and master cylinder when I put the 6 piston Brembo/13.9" rear rotors on the car with 302S ABS module. Did this as both an upgrade and preventive maintenance.
Steve
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Just a update, never really got the brake peddle going hard problem fixed. We checked for vacum leaks and varios other minor changes with no real affect. Now another 2013 Gt with automatic has upgraded to the brembos and he is having the same problem. They have to put the brake on with anticipation and softly to avoid the hard peddle. Any reason why it would only affect automatics??
 

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