After hearing someone else crashed last week due to loss of brake pedal i figured i would share my excitement.
On a qualifier at epping i pulled the chute through the traps and waited for the hit...and waited and waited...finally realizing i was running out of real estate, i jumped on the footbrake and handbrake hard.The pass was 218mph and she was coming up on the turn off a bit quick.As soon as i was about to make the turn i completely lost the footbrake,right to the floor.Thank god for the handbrake and i kinda slid into the return road.
Getting out of the car i saw that the chute just dropped out and got tangled in the wheelie bar,never deploying. Obviously i boiled the fluid in the caliper because by the time i got back to the pits i had a good pedal again.
Realizing this fluid was probably 10 years old i tried to flush the brake system but all the bleeders where frozen.
Ive always replaced the pads and rotors but never thought of flushing the brake fluid or rebuilding calipers after a certain number of runs.
Thank god for my hand brake or i would have definitly had a huge problem.

Mike, you got lucky! You should be flushing your brake system every season and filling it with DOT5 as I do, which you'll never boil. Had I known your fluid was 10 years old when I saw you at Epping, I would have told you we're flushing it right now!

I agree that you should be spending $15 a year to flush your brake fluid. Ed is only .1 wrong on this. Use 5.1 that is compatible with all other brake fluids if you get in case you get in a bind.

How much Material was left on your pads? I ran 5.1 Fluid and replaced it Often yet have boiled the fluid more than once with pads reaching end off life. Glad you had a hand brake. I always encourage racers to add this feature. You just never know when the Swiss cheese holes are going to Be aligned. I rolled and destroyed my ‘92 Horton on 2000 when my Shute didn’t work after a quick 16 pass. Ended up on top of the berm at the end of the old morose track and on fire.

Paul confirms, 5.1 boils too!

As I have stated numerous times here DOT5 and flush your brake system every season.

All race brake fluidS list the max temp in print. 5.1 is ~525F (if free of water moisture). Add 100F if a Dot 4 race fluid is your thing. I only used 5.1 in recent years. It’s a derivative of Silicon and less corrosive then an Dot 4.

I am not doubting that brake fluid will indeed boil and cause big problems. But if brake fluid boils, putting air in the system, how after the fluid cools does the pedal return without bleeding the air out of the system? To me that is impossible.

Also almost 30 years ago I had no chutes at 230+ MPH on our T/AD, I did just get stopped before the sand trap, when I climbed out of the car the brake rotors were still red and smoking, but I never lost the brake pedal (actually lever). There was just DOT 3 fluid in the system. Was I just lucky?

So why is Ed changing the brake fluid. Dot brake fluid attracts water like a magnet. Dot 4 especially. As it gets very moist, the advertised max temp can drop over 200F.
Good idea to change it, especially if you live in a humid area like South Fla. it can be as easy as turkey baster suck the master empty, refill with new and bleed each caliper. Maybe a 30 min task.

quote:

I am not doubting that brake fluid will indeed boil and cause big problems. But if brake fluid boils, putting air in the system, how after the fluid cools does the pedal return without bleeding the air out of the system? To me that is impossible.

bender i wish i could answer that one...i thought for sure i had blown a line or a seal out of the caliper...but when i got back to the pits the master was full,i had no leaks and a good brake pedal

quote:

Originally posted by "The Bender":

Also almost 30 years ago I had no chutes at 230+ MPH on our T/AD, I did just get stopped before the sand trap, when I climbed out of the car the brake rotors were still red and smoking, but I never lost the brake pedal (actually lever). There was just DOT 3 fluid in the system. Was I just lucky?

I’d bet your fluid was fresh and on the dry side and your brake pads close to or new. You would be surprised how much a brake pad insulates the wheel cylinder pistons when new. Like space shuttle tiles, kind of.

quote:

Originally posted by jenavet:

quote:

I am not doubting that brake fluid will indeed boil and cause big problems. But if brake fluid boils, putting air in the system, how after the fluid cools does the pedal return without bleeding the air out of the system? To me that is impossible.

bender i wish i could answer that one...i thought for sure i had blown a line or a seal out of the caliper...but when i got back to the pits the master was full,i had no leaks and a good brake pedal

I think the water in the fluid boils to steam and back to water as the fluid exceeds 212F. Just a guess

quote:

Originally posted by adv ET 266:

quote:

Originally posted by "The Bender":

Also almost 30 years ago I had no chutes at 230+ MPH on our T/AD, I did just get stopped before the sand trap, when I climbed out of the car the brake rotors were still red and smoking, but I never lost the brake pedal (actually lever). There was just DOT 3 fluid in the system. Was I just lucky?

I’d bet your fluid was fresh and on the dry side and your brake pads close to or new. You would be surprised how much a brake pad insulates the wheel cylinder pistons when new. Like space shuttle tiles, kind of.

You would be right about the pads being thick.....

I had a similar deal to Mike. It was single caliper and worked good enuff to make the turn at E-town going 40 mph. My pedal/feel was terrible until I changed the fluid.

I bleed my brakes about every two weeks or so. Pedal feel for me on the starting line is very important to me. I use the high temp brake fluid but I am sure i am still boiling it from time to time.

You won’t boil DOT 5

I put dual brake system with separate master cylinder on my old altered and will probably do it with new car.

I think that is a good idea for any fast car.

Looking up boiling points of brake fluid it reflects that DOT 5.1 has a higher boiling point than DOT 5 by 18 degrees.

Why do you believe you won't boil DOT 5?

I am not saying it's a bad choice but it will boil and before 5.1.

DOT 3 Dry 401°F, Wet 284°F
DOT 4 Dry 446°F, Wet 311°F
DOT 5 Dry 500°F, Wet 356°F
DOT 5.1 Dry 518°F, Wet 374°F

I would agree time is the culprit on significantly reducing the boiling point and changing it regularly will help to mitigate this.

Any liquid that is heated above it's boiling point becomes a gas, then when it cools it becomes a liquid again. Chemistry 101. So yes, you can lose your pedal then get it back again.

This assumes a closed system, of course. Air condition is essentially nothing more than a refrigerant in a closed system that is constantly cycling between a liquid state and a gaseous state.

This is an interesting topic - it also set me to thinking about something like a NASCAR stocker or an Indy or F1 car that generates a ton of brake heat without boiling fluid. Maybe an added safety feature for you guys with big MPH dragsters would be cooling ducts to your brakes?

quote:

Air condition is essentially nothing more than a refrigerant in a closed system that is constantly cycling between a liquid state and a gaseous state.

Hey, Mr. Chemist. A/C system is a closed system. So why does ambient temperature and humidity affect gauge readings?