Brake Fluid Boiled... i have some questions for you
 

I would like to know if others have had the same experience as me...there is some backstory after my questions. Thanks!

After brake fluid boils, is it common for it to burst out of the caliper check valves?

If that is not common and the gaseous brake fluid is still in the system, will it eventually condense back into a liquid and you can drive away safely? And if so, should you flush and replace your fluid after it has boiled?

If someone has boiled their fluid before, did you have a strong brake fluid smell from inside the car? I haven’t had a chance to thoroughly clean up the calipers, but the smell from inside is far stronger then on the outside close to the calipers. It doesn’t appear to have any fluid around the pedals so I’m wondering if there is another place it could of leaked?


Some back story: This past weekend I did my first track days at Sebring. I’m running hawk 5.0 pads in the akebono calipers, solid rotors, SS lines, and motul 5.1.

On my last session of the weekend, they let us stay out a full hour on track and I stayed out without coming in to cool down. I ended up boiling my brake fluid.

When I got off track, I had absolutely no brakes, no fluid in the reservoir, and the fluid came out through the caliper valves. Lost some paint in the process. Cabin gas a strong brake fluid smell now


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I’m sure many will chime in here, but after doing many many many track events, I will try to answer some of your questions and give you some advice.
First off, you need brake cooling ducts. Period.
Now that’s out of the way, I would say it is not normal to lose your fluid out the bleeders after the fluid boils. My last track event at Road Atlanta I did lose some fluid out the front outer driver bleeder, but never lost my pedal, didn’t have any smell. I believe the bleeder screw was a little loose. Luckily it didn’t affect my paint on the car.
The one time I did boil the fluid was at Carolina Motorsports Park where there are moderate braking zones, but little straights to get them cooled enough. I lost pedal pressure near the ends of my 25 min sessions, but after driving around the paddock it came back. I did not have any fluid leak from the bleeder screws. I absolutely recommend changing the fluid after that circumstance.
I’ve got nothing for you in regards to your smell inside the cabin. Sorry.

If you boiled the brake fluid. Flush it!!!

'bono's are great at leaking fluid from the bleeders when hot. There is a thread on the subject.

As said. If you don't have cooling ducts. Get them.

The smell. Boiled fluid on the rims, and thrown off.

I always assumed that if you got brake fluid all over calipers and rotors hot enough to boil the fluid that you'd have a fire on your hands. Good to know that's not the case.

Thanks for the input guys!

I searched around and found the thread about the calipers leaking through the bleeders.

Looked like there were a few opinions going around there as to what was happening. One guy said he installed a helicoil and it fixed the problem...

Rusty, what did you do to fix the problem?


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Nothing. Mine still leak sometimes. :shakes head: Thinking about AP Radical calipers.

You still can have a fire if you get enough fluid on stuff. Leaking from the bleeders. I wouldn't think so.

You sign up for Jan 6th, I’ll be out there.

Wow that's some boil over, brake fluid is corrosive so keep an eye on the conditions of parts that were exposed to it as to limit further corrosion. The smell will eventually go away as any residual fluid brakes down with time.

When you change your fluid use one of the below or better and get a simple fluid tester for % water content.

Motul 5.1
Dry boiling point 269 °C / 516 °F
Wet boiling point 187 °C / 369 °F

Motul RBF 600
Dry boiling point 312 °C / 594 °F
Wet boiling point 204 °C / 399 °F

Castrol SRF
Dry boiling point 310deg C
Wet boiling point 270deg C

Added the F temps to the Castrol. ;)

Just bought 2 bottles of Castrol SRF. That was $130. Cheapest place was Amazon.

Did you not notice change in pedal feel before the end of the session? If so, there's no excuse for staying out, especially in an hour long session, as you're begging for serious damage to your car and possibly another. Brakes don't deteriorate from normal to full boilover in one lap; so hope that you learned from this. And for others, don't ignore change in pedal feel and hope all is OK!

I only use Castro SRF and I have never had an issue with boiling the fluid. When it comes brakes just like you cooling and oil system...everything must be done to the maximum benefit of cooling.

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Sometimes they don't but then sometimes they do. It takes some time for the heat to go through pad material and caliper and get the fluid over the boil point. It sometimes happens as your finishing your braking and they go soft and can take appropriate action. But there's nothing preventing you from having perfectly good brakes after one brake zone and none on the next. This is why people stress the importance of good clean fluid and good cooling. If there was a simple way to predict when your brakes were going to give out people wouldn't be as crazy about them.

I was at an event Saturday and lost my brakes in my 3rd session when the instructor told me to stop babying the brakes. I went 10/10ths for about 5 laps and the pedal went to the floor after a hard sequential hard S section. I knew I boiled the brakes and pitted early. Had the techs take temps of tires and the brakes. They were claiming that the calipers were 850F degrees.

I am on the Akebonos with the Z1 2-piece rotors and Hawk DTC 60/30 pads. I'm using RBF-600 fluid.

Additional info: Running a supercharged G37 coupe @ a claimed 370 whp tune for the track.

How much do you guys think ducts could reduce the boiling or has the car's configuration just overpowered the brakes?

Cooling ducts will help a lot. And get some Ti heat shields to go between the pistons and pads.