Brake Issue: Installed F14 Front Kit and New Rear Rotors/Pads - Still having issue

[Silver TT]

I finally got around to installing the Vintage Venom F14 front brake kit and it is great. The kit comes with 14" Brembo rotors with huge 4 piston monobloc calipers. Fit and finish is outstanding and this kit is a HUGE improvement over the stock Cobra front brake setup and really brings a much better level of balance to the car.

Was having a brake issue before installing the F14 kit - but was hoping it would go away with the new front setup. Unfortunately it didn't so I'm confused as to what to do next. After a fast acceleration if I quickly stab the brakes the car jerks slightly to the left and there is very little braking force front or back...the pedal is really firm and never drops to the floor but the pedal feels sort of "stuck" up high and there is no brake power at all really. If I quickly release and then reapply the brakes the car will have perfect braking power. I should mention this is only on my first hard stab of the brakes. On subsequent hard braking it works fine.

Since I changed all 4 rotors and pads when I did the F14 install the only thing I didn't replace is the rear calipers. I also flushed all the brake fluid and installed Motorcraft high temp (500 something fluid). Is it possible I have a bad caliper in the rear which is causing the car to jerk left? What is strange is it feels like I have no brakes, not just 3 out of 4. Think it could be something with the master cylinder or another component in the system?

Any help is appreciated. Want to get this sorted out so I can really feel the performance of the new setup.

 

[Silver TT]

Spoke to a former Ford engineer involved in developing the original braking system on our car and he actually said this is "normal." Called it a known issue of "spike apply" something about the hydroboost not being able to produce hydraulic pressure on first stab and just getting mechanical hydraulic pressure.

Said they tried lots of things to solve the problem but ultimately never found a solution so all cars experience this from time to time.

Anyone else have this situation?

 

[Saleen4971]

Could try speaking with van at vancopbs. He is a God with hydroboost, maybe he would have an idea.

Sent from my MB860 using Tapatalk 2

 

[006]

I recently fixed a similar jerk to the left brake problem without realizing that it could be the culprit.

The left control arm balljoint was locking up.

Might not be your particular cause, but something to have a look at while you're down there. Check for ripped boot and dried up grease (p.s. The boots can be replaced).

Other culprits could be the hoses. Check for kinks on them and the hard lines as well.

 

[Bruha]

Subin

 

[Silver TT]

I recently fixed a similar jerk to the left brake problem without realizing that it could be the culprit.

The left control arm balljoint was locking up.

Might not be your particular cause, but something to have a look at while you're down there. Check for ripped boot and dried up grease (p.s. The boots can be replaced).

Other culprits could be the hoses. Check for kinks on them and the hard lines as well.

Thanks 006. Was your issue occuring all the time - like on every press of the brakes it would jerk slightly to the left? Mine only happens on first time.

Kind of feels like a caliper piston is stuck or something which causes the whole system to lock up temporarily and the car jerks lightly to the left maybe because right rear caliper is stuck but left rear works fine?

Strange thing is it always works fine - good brake pedal pressure, good braking force, and no jerk left or right after the system is warmed up and I've done a few stops. But it is really annoying and I want to get it diagnosed so I can confidently rely on the brakes at all times.

Maybe I'll swap out the rear right caliper. Was thinking it might be time to rebuild or replace anyway.

 

[Bruha]

This is interesting. I have been thinking about this. I have the same brake kit. I did install new rear rotors, and I am running carbotech pads front and rear , and I have no issues whatsoever. My buddy has them too, and no issues. Have you tried calling Rob from vintage to see if he has an idea??

 

[Silver TT]

This is interesting. I have been thinking about this. I have the same brake kit. I did install new rear rotors, and I am running carbotech pads front and rear , and I have no issues whatsoever. My buddy has them too, and no issues. Have you tried calling Rob from vintage to see if he has an idea??

Hey Bruha - Want to be clear, this issue has nothing to do with the Venom F14 Kit. I had this exact issue BEFORE install of F14 kit. Was just hoping it would go away after replacing about 80% of brake hardware (front rotors/calipers/pads and rear rotors/pads) but it did not. Only thing I didn't replace is rear calipers which is making me think the issue is either one of the rear calipers (most likely right rear since car jerks to left) or something to do with master cylinder, etc.

 

[Bruha]

ok, I understand now. Seems like master cylinder to me. I could see where a hanging front caliper would jerk the car, but I am not seeing a rear doing that.

Just out of curiosity, did you realize the lines sent with the kit had specific sides for installation? I am sure you probably did. Just wondering.

 

[Bruha]

I still think Rob would give you an idea though. Might be worth the call.

 

[Silver TT]

Thanks for additional ideas. Yeah, I noticed the lines were specific to each side. The fronts are working great - huge stopping power.

In fact the car runs / stops amazingly well 99% of the time. Its just on that first application of the brake when the pads are cold I get the slight jerk to left and very limited braking force. This has been happening since day one when I got the car from prior owner.

Only other issue I have noticed is a very slight vibration when rolling up to a stop when I have foot on the brake. Also has been occurring since day one. Could this be related to a bad master cylinder?

 

[Silver TT]

Drove the car about 300 miles last weekend so have a lot more data to share. Bottom-line is the car drove just about flawlessly, no loss of braking power, no jerking to the left on hard stops - drove like a new car for about the first 200 miles and I figured the issue was gone.

Then I found a nice open stretch and wanted to do some testing to make sure all was good. I did a nice long pull through first, second, and up to about 5000 rpm in third when I rolled right from the throttle to brake and it happened. Car had very little braking power, almost like someone was pushing up on the pedal against my foot pushing down and the car pulled slightly to the left. Its like the rear left caliper works but the other three don't engage at all for a split second. I quickly lifted and reapplied brake and car stopped just fine. Then I did another real hard stop from about 70 mph and ABS activated - car stopped great with just a little bit of tire squeal. So I tried to replicate the acceleration immediately followed by braking and was able to produce the unwanted result one more time in 3rd, but on no other time did the car act up the entire 300 mile trip. It only seems to happen on very aggressive acceleration runs above a certain speed followed by a quick application of braking.

97% of the time the car stops beautifully. 3% of the time I can replicate this issue and it only lasts a second or two. Could that be from an issue with the Hydroboost? Would a Ford diagnostic help?

 

[TwinTurbo4vGT]

Its the hydroboost. I just had the same issue with my truck. try pushing the brake pedal all the way to the floor, if the idle goes up slightly the hydroboost has gone bad. There is a tiny diaphram inside and they tear causing vacuum leaks and they dont work properly. Hope this helps.

 

[Silver TT]

Its the hydroboost. I just had the same issue with my truck. try pushing the brake pedal all the way to the floor, if the idle goes up slightly the hydroboost has gone bad. There is a tiny diaphram inside and they tear causing vacuum leaks and they dont work properly. Hope this helps.

Thanks TT4vGT... Would be great if I could diagnose it to be that for sure. Will check the brake pedal / idle reaction tonight when I get in the car.

If it does turn out to be the hydroboost can you just replace the diaphram or do you need a whole new unit?

Looks like about a $255 part at Tousley.

2004 FORD MUSTANG Parts - Tousley Ford Parts Depot

 

[TwinTurbo4vGT]

Thanks TT4vGT... Would be great if I could diagnose it to be that for sure. Will check the brake pedal / idle reaction tonight when I get in the car.

If it does turn out to be the hydroboost can you just replace the diaphram or do you need a whole new unit?

Looks like about a $255 part at Tousley.

2004 FORD MUSTANG Parts - Tousley Ford Parts Depot

sadly you have to replace the whole unit. Luckily you reuse the master cylinder. BTW what part of NYC u in?

 

[Silver TT]

Live just south of Union Square. Let me know next time you are in city or if anything good is going on locally and we can meet up.

In meantime I am going to try and find best place to do the hydroboost repair. If anyone has seen a good DIY with pics I might do it myself but haven't done much hydraulic work before other than brake / rotor / caliper / lines, etc.

 

[TwinTurbo4vGT]

Oh ok thats not bad. Yea when i get my car on the road sometime this week we can definitely go to some shows :rockon:

 

[Silver TT]

TT4VGT - Let me know if you hear of anything local going on - we can meet up somewhere.