Hot brakes, soft pedal, didn't come back much

[9746Cobra]

Ran a one mile, eight turn track event yesterday. Max speeds 85-90mph. I did not have brake ducts because the speeds are so low I didn't think they'd be of much help. Most of the track is around 45mph or so.

My brake pedal got a little softer after the first run and continued to get worse. I skipped a run at the end because the pedal was so soft. (3/4 to the floor and I had to pump it up)

The pedal did come back mostly on the drive home, but today it still feels softer than it used to.

Another Mustang with the same Mach/Cobra brakes had the same issue, but his were pretty bad this morning.

If the brakes were just faded or the fluid boiled (ford Heavy Duty fluid, PBR pads, stock hoses, stock rotors) why did they not get much better after cooling for a day?

Were going to flush and bleed them ASAP and see if they return to normal.

One more thing:

While cooling down in the pits I noticed brake fluid coming out from under the cap. It was right at Max before, but when I removed the cap it was overflowing. I soaked out some to get the level back down. I didn't know brake fluid expanded so much. (?)

9746C

 

[wheelhopper]

Your brakes get worked much harder on shorter tracks. Even repeated stops from 45mph are harder on the fluid than stops from 90mph with cooling time between.

Sounds to me like your fluid had a lot of moisture in it. That is why it boiled over so easily. Once that happens you fluid is toast. Flush out the entire system and you should be fine. I know people speak highly of the Ford fluid but I have been using the Valvoline Synpower with lots of success. I have actually come off the track with the brakes smoking and still have great pedal pressure.

 

[truebluecobra]

.

 

[truebluecobra]

!

 

[9746Cobra]

There we go.

 

[ac427cobra]

Bleed your brakes and you should be fine.

One other thing, you don't want to run your reservoir too full. It will come out and get on your valve covers and eat the paint off of them! Run the fluid about 1/4" to 3/8" down. Also wrap a rag or disposable shop towel around the reservoir and tape it nice and neatly. If you do this, any fluid that comes out gets soaked up by the rag and not your engine paint.

Always go to the track with fresh fluid and flush after the event.

FWIW



:thumbsup::coolman::beer:

 

[David Hester]

I agree.
You didn't say if you bled your brakes before going out.
Always a good idea. I've found that once they boil, they won't "Fix" themselves.
Bleed with fresh fluid- All the way till you see nothing but clean fluid, not just no bubbles.
I'm one of the ones that has used Ford HD (now Motorcraft Heavy Duty) since the mid 80's in everything from street cars, autocross cars, race cars, to Formula Fords. Works great.
I just bought some Wilwood 600 and will use it in the the race car, but will continue to use Motorcraft HD nee Ford HD in the street/ autocross/ tow vehicles.
http://www.wilwood.com/Products/006-MasterCylinders/012-EXP/index.asp
http://www.wilwood.com/Products/006-MasterCylinders/012-EXP/tech.asp

 

[David Hester]

Another thing, check your pads. Are they glazed? That won't fix itself, either. Light sanding paper will, though.

 

[9746Cobra]

I only "gravity bled" them with Ford heavy duty. I didn't expect this track to be hard on brakes. Oops!

I need to remove the pads and bevel the edges anyway. They sqeal a little. I machined all four rotors (Factory rear, Brembo front) recently then bed in the pads some.

Are brake ducts much help on a short track like this?

 

[wheelhopper]

Anything that will help cool the brakes will help. Get the brake ducts. You will need them at some point anyway.

 

[9746Cobra]

Anything that will help cool the brakes will help. Get the brake ducts. You will need them at some point anyway.

I've got the backing plates mounted on the car already. Have the hose too. I just need to order the adapters for the fog light holes.

Just not sure if it's worth the trouble on a short track.

 

[gcassidy]

Bruce (and all), I found those terry cloth elastic wrist bands at sports stores fit perfectly around a Ford m/c cap. Mine's been on for 3 years now, stopped my overflow issues, and looks snazzy (yeah, that's a word!).

 

[David Hester]

Snazzy.
Adding that culture thing again. ;-)
Those might be a good idea around power steering filler, too.
Neato!

 

[gcassidy]

Snazzy, right? The Michael Jordon Signature Series.

 

[9746Cobra]

Bled the brakes, they came back just fine.

Thanks!

 

[wheelhopper]

Good news.


Greg, I never noticed your "elastic brake fluid resevoir cover". So you can add stealthy to the list.

 

[Jimmysidecarr]

I only "gravity bled" them with Ford heavy duty. I didn't expect this track to be hard on brakes. Oops!

I need to remove the pads and bevel the edges anyway. They sqeal a little. I machined all four rotors (Factory rear, Brembo front) recently then bed in the pads some.

Are brake ducts much help on a short track like this?

Ford changed the formula on our brake fluid a couple years ago when they changed the part # from PM-1 to PM-1-C.
The dry boiling point went from 550F to 500F.
That's when I stopped using it for open track. It's still good stuff, just not the outstanding "value racer" item that it used to be.

I have been using ATE super blue but it's all gone so I think I'm going with Wilwood next time. Lots of real racers use it and it's reasonably priced.

Why does it need to be reasonably priced when brakes are so critically important?
Because it gets dumped out and replaced A LOT!

On the brake ducts topic: DO IT! Short tracks, long tracks, whatever.
You will enjoy longer pad life, more consistent and repeatable brake performance, and will be able to run faster and longer with street/track combo compounds before having to step up to track only race pads.

I put ducts on before my 1st ever event(TWS summer 2004), I only had the hoses and aimed them into the center of the rotor, zip tied to the tie rods and spindle.

I have never had brake fade. Not from pads or fluid. I've had tires get over heated, but not brakes. I like to stay ahead of my ability as a driver with capable brakes and compatible compounds for wherever my skill level happens to be at.

There is less time at speed on short tracks to wash air through your rotors/brakes, before you have to hammer more heat into them.
Even though the speeds are lower, and each braking event seems less intense, it is the time off the brakes that is missing on the short tracks.
The only time they can cool, is when you are off the pedal.

 

[Todd TCE]

I just bought some Wilwood 600 and will use it in the the race car, but will continue to use Motorcraft HD nee Ford HD in the street/ autocross/ tow vehicles.

Great fluid but a note of caution; this is not really street fluid. The elevated temp range will more rapidly degenerate than fluid such as 570. Only those vehicles really needing the temp range of the EXP should consider it. The working life is too short for most folks.

Same rule of thumb applies; "if you don't boil what you use now, you don't need higher bp fluid"

 

[David Hester]

What Todd said.
I wouldn't use it is a street driven car.
Wilwood advises against it too.
Another thing, Wilwood says don't mix it with other fluids. If you do use it for track days, flush out competely (again), if you are going back to Motorcraft or whatever.

 

[9746Cobra]

Thanks guys.

I've used brake ducts on a faster track and they made a huge difference.

I'll get them for this car and try them on the slower track. I also might get some better brake fluid. Perhaps Valvoline synthetic.