Attention all brake doctors; need advice/help

D

ddl6289

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After doing lapping days at Blackhawk Farms Raceway with the '03 Mustang Cobra on Saturday, the I came back with the following problems:

1) Glazed front rotors with hairline radial cracks in the glazed portion,
2) Dust boot on caliper pistons melted and/or cracked,
3) Evidence of brake fluid boil over,
4) development of loud clunking noise upon hard braking

I had Hawk HP Plus pads in the front. I bedded/burnished according to instructions. When I got home I took the Hawks out and put the stock pads in. The Hawk pads, which were new before the event, were heavily worn. Still have the loud clunking noise upon hard braking. With heavy braking the pedal goes past the normal range of motion almost to the floor with the clunky sound becoming very pronounced.

Help! Do I have a major brake problem to deal with here? Let me have any thoughts you all may have.
 
i8u

i8u

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When you changes the pads did you let the resivoir get to low causing air to get sucked into the master cylander? This would explain the low pedal. Does it feel spongy compared to how it used to feel?

Can you tell where the clunking is coming from? Can you feel it through the brake pedal?

I would get it fixed as soon as possible. Brake problems are not something to take lightly.:beer:
 
ShelbyGuy

ShelbyGuy

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tire rack has genuine brembo rotors on the cheap. motul 600 is your friend, as is the motive products power bleeder.

two words: brake ducting. 00R ducts on the knuckle connecting to the open hole next to the fog lamp is an easy, available mod.

you dont have a major brake problem, you just overheated and wore out your brakes. you need to freshen them up now. no biggie. i bet you will find what makes the clunk as you replace worn out bits.
 
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ddl6289

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No. The brake light does not come on. I'm going to completely flush the system and repalce with Valvoline synthetic or Prestone Dot 4 for the time being for the street. My next track day isn't until the end of Sept (Blackhawk)/ beginning of Oct (RA). I definately won't go back on the track until I have this issue completely sorted out. Can one use old pads with new rotors or should both be replaced simultaneously? Is the melting of the dust boots normal? bad? really bad??
 
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fiveoguy

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1) I'm not sure why your rotors cracked, the stock Brembo pieces should hold up pretty good. You may want to invest in some good heat treated ones, I like porterfield myself. http://www.porterfield-brakes.com/

2)When you run the car on the track, you are making a LOT of heat with all the heavy braking. Melting the dust boots is normal, and not really something to worry about, not much you can do about it. Maybe someone makes some that are more resistant to the high heat, but I wouldn't worry about it.

3)You need some better brake fluid. The stock stuff is ford heavy duty, which is very good, but it sounds like you need higher temp stuff. I'd say Motul 600 as mentioned above. This is why your pedal is mushy, you boiled the fluid and now it has air in it. When you hit the pedal, the air compresses and gives you the mushy feel. Flush the system with some good high temp fluid.

4) Not sure about the clunk, definitely not normal. Replace your pads and fluid and see if its still there.
 
toofast4u

toofast4u

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Originally posted by ddl6289
No. The brake light does not come on. I'm going to completely flush the system and repalce with Valvoline synthetic or Prestone Dot 4 for the time being for the street. My next track day isn't until the end of Sept (Blackhawk)/ beginning of Oct (RA). I definately won't go back on the track until I have this issue completely sorted out. Can one use old pads with new rotors or should both be replaced simultaneously? Is the melting of the dust boots normal? bad? really bad??
Click to expand...

1) The best brake fluids are Ford High Performance Brake Fluid which has a 550 degree boiling point and Motul Racing Brake Fluid which has a 585 degree boiling point. I use the Ford stuff because it works good and is a lot cheaper the Motul. Buy the Motive pressure system it makes changing fluid easy and fast. Change the fluid before every track event.

2) Switch out the stock rubber hoses with a good DOT stainless steel hose. I like the MM hoses as they have banjo fittings to allow correct alignment and a clear urethane covering to protect the steel braid from damage.

3) Buy a good set of pads depending on applications you might want to change between a good street pad and rotor set-up and track set-up. Don't buy rotors that are drilled they are cracked prone, but a good set of slotted will work well. The stock pads suck and if you did this with the stock pads that can be the root of everything you experienced.

4) Melting the dust boots is normal and nothing to be concerned with. They are a soft rubber bushing and I don't no anyway to correct this. I know several people who run without them without any issues.
 
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NJStangFan

NJStangFan

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Originally posted by ShelbyGuy
two words: brake ducting. 00R ducts on the knuckle connecting to the open hole next to the fog lamp is an easy, available mod.
Click to expand...

And where does one buy that??? :)
 
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03SVTCOBRA10TH

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CUSTOM FORD POWER BLEEDER KIT. Comes with both 2 prong and three prong adapters to fit most late model Ford cars and trucks. All bleeders come with everything you need to bleed your hydraulic brake or clutch system and our full 1 year warranty. Application Guide. (Model 0253)
Qty: Price: $69.95

CUSTOM FORD POWER BLEEDER. Comes with everything you need to bleed your late model Ford hydraulic brake or clutch system and our full 1 year warranty. (See our Application Guide for vehicle compatibility.) Please choose adapter. (Model 0106-7)
Qty: Price: $54.95
Adapter:
2 Prong3 Prong

Which kit?????????
 
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jmimac351

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First time out on stock pads/fluid I boiled the fluid.

Second time out I replaced the fluid with Motul 600. That was the only change... did not boil the fluid.

3rd time out I replaced the stock pads with Carbotech XP9 (front) and XP8 (rear). The car stopped like a "sum b!tch". Did not boil the fluid.

I will be adding the ducts but will just tie the hose to the tie rod.

This is on a course that is about 1.5 miles. It's the road racing track at the Gainesville Raceway in FL. Top speeds are about 95mph but with a couple of hairpin turns where you brake from 95 to about 15mph.

These will help you bleed the brakes by yourself:

https://www.speedbleeder.com

Jim
 
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