Brake bleeding if it boils... how much to bleed off?

[bpu699]

Figured I would ask as I haven't seen it posted...

If your pedal gets spongey on a track day...

1) How much brake fluid do you bleed off to get back to normal? Is it just a bit off each caliper nipple? Or are we talking about flushing the whole system out? Assume new fluid, not water logged...

2) Does brake fluid get "damaged" when it boils over? If you just let the car cool off, are you back to normal? Again, asssuming the brake fluid is fresh...

[Tobra]

The solution to pollution is dilution. If you cook some of the fluid, I think you should flush it out pretty well. Brake fluid is pretty cheap.

[JeremyD]

the whole system - I usually use a turkey baster to remove all the fluid in the resevoir - the start with all new fluid

[Quinlan]

If new fluid is boiling, you are probably:
1. Using the wrong fluid (should be using a higher boiling point);
2. Not using brake cooling ducts;
3. Driving a very heavy car on a tight road course, and/or
5. Using the brakes too much

Replacing the boiled fluid with new fluid, without changing either the car or driving habits, will not help you.

[Trackrash]

Originally Posted by bpu699

Figured I would ask as I haven't seen it posted...

If your pedal gets spongey on a track day...

1) How much brake fluid do you bleed off to get back to normal? Is it just a bit off each caliper nipple? Or are we talking about flushing the whole system out? Assume new fluid, not water logged...

2) Does brake fluid get "damaged" when it boils over? If you just let the car cool off, are you back to normal? Again, asssuming the brake fluid is fresh...

Do you mean spongy on the track or after you get back the pits?

[KTL]

You don't necessarily have to flush the entire system. Brake fluid, like motor oil, is a poor conductor of heat. So I would bleed enough fluid out of each bleed nipple to of course get rid of the bubbles and also some additional heat-affected fluid.

When the fluid boils, it doesn't return to normal upon cooling. Those bubbles remain in the caliper for a while and don't go back into solution. The bubbles will reduce in size but they'll still be there. So you'll still have a soft pedal.

Thankfully the 930 brakes you have are up to the task of track duty. The Carrera and SC cars of the same age are not as fortunate. To shield the fluid from heat, it's worthwhile to use Ti pad shims/shields because titanium is a poor conductor of heat. The shields reduce the heat transfer from to the pistons (and 930 pistons are anodized aluminum alloy, which unfortunately is a fairly good conductor of heat and we don't necessarily want that) and that also reduces heat transfer to the seals and fluid

[Trackrash]

Originally Posted by KTL

To shield the fluid from heat, it's worthwhile to use Ti pad shims/shields because titanium is a poor conductor of heat. The shields reduce the heat transfer from to the pistons (and 930 pistons are anodized aluminum alloy, which unfortunately is a fairly good conductor of heat and we don't necessarily want that) and that also reduces heat transfer to the seals and fluid

Ti pads? Source?

[RichardNew]

This is interesting. If you're boiling the fluid something is wrong. I can run 1200 degrees at the rotor and the brake fluid never even reaches 300 degrees. Very little heat actually transfers to the brake fluid inside the caliper.

I think you have a bunch of water in your brake fluid. Water boils at 212-degrees. You're undoubtedly over 212.

I seriously doubt that you're actually boiling the brake fluid. You're boiling the moisture. Once you get over 212 degree the moisture becomes steam. Steam is compressible. That's why the pedal goes to the floor on you.

I would do a total flush of the brake system. You may want to do a flush using denatured alcohol. Then follow that with new fluid. Any quality fluid will work.

One other thing you might consider is that your pads might be thin. Pad material acts as an insulator. As the material becomes thinner more heat is transferred to the caliper.



Richard Newton
Monitoring Your Brake Temperatures

[bpu699]

Thanks for the input. I actually haven't had any problems boiling brake fluid, but others have. What I see on the track is guys just bleeding off a couple ounces on each nipple if that...

Just wanted to know if that's the correct way... I am no where near boiling off brake fluid... I have heavy duty fluid good to 475 degrees in the car, as that's all the local places sell. I bought some more ate 200, but haven't put it in as the stock stuff seems fine...

Was at Blackhawk farms yesterday, and had a ball. The 930 flies. After the third session started getting a slight shimmy under hard braking. Hope I didn't warp a rotor... Driving home on the highway, there was no shimmy... Plan to change the pads and see if that matters...

[sugarwood]

Is it safe to say that "racing fluid" is overkill, and you're really just better off having clean fresh fluid devoid of water?

What is that red area on the brake rotor?

[Emo993]

Thanks Richard for the brake fluid information and the rotor tempature paint insight. Best, Mark

[Bill Verburg]

Originally Posted by sugarwood

Is it safe to say that "racing fluid" is overkill, and you're really just better off having clean fresh fluid devoid of water?

What is that red area on the brake rotor?

It depends on the system, car and use.
RN's got nice racing brakes w/ I'll bet nice racing pads, the rotors are big enough to first absorb pad heat, w/ an efficient core design and construction they will then transfer that heat to the atmosphere quickly, the second line of defense is the racing pads that work well at higher temps and will usually have decent thermal brake built into them, they will still want to be changed at ~50% , the last line of defense is the brake fluid, there are many levels of thermal protection available here, the best is Castrol SRF but only the most thermally stressed systems will need that, some unstressed systems can even get away w/ ATE blue/yellow that come stock in most German cars, most use something in between,

here are some of the best choices in order of wet boiling points
brand type wet boiling dry boiling mixable w/ other of the same type oz/container $/oz list price
Castrol React SRF 4 518 608 Yes 33.8 2.07 69.99 https://www.google.com/#q=Castrol+SRF+brake+fluid&tbm=shop

Torque RT700 4 439 683 Yes 16.9 2.01 33.95 https://www.google.com/#q=Torque+RT700+brake+fluid&tbm=shop


Endless RF 650 4 424 622 Yes 16.9 2.49 42.00 https://www.google.com/#q=Endless+RF650+brake+fluid&tbm=shop

Neo
Synthetics Super Dot 610 4 421 598 Yes 16 1.56 24.99 Super DOT Brake Fluid

AFCO HTX 4 421 618 Yes 16.9 1.18 19.99 https://www.google.com/#q=AFCO+HTX+brake+fluid&tbm=shop

Galfer Super DOT 5.1 5.1 419 572 Yes 16.9 0.83 13.99 FLUID DOT 5.1 motorcycle

Wilwood EXP n/a 417 626 Yes 16.9 1.05 17.69 http://www.tce************************/service-parts/

Comar GS610 4 417 626 Yes 16.9 0.89 15.11 https://www.google.com/#q=gs610+brake+fluid&tbm=shop

Maxima SYN High-Temp 4 410 600 Yes 12 1.25 14.95 Brake Fluid - Maxima Racing Oils motorcycle and auto

Bel-Ray Racing 4 410 580 Yes 12 1.25 14.99 https://www.google.com/#tbm=shop&q=Bel-Ray+racing+brake+fluid motorcycle

Motul RBF 600 4 401 594 Yes 16.9 1.06 17.99 https://www.google.com/#q=Motul+RBF+600+brake+fluid&tbm=shop

I like Motul 600 's price/value mix, but my cars can get away w/ ATE

[Bill Verburg]

Originally Posted by bpu699

Figured I would ask as I haven't seen it posted...

If your pedal gets spongey on a track day...

1) How much brake fluid do you bleed off to get back to normal? Is it just a bit off each caliper nipple? Or are we talking about flushing the whole system out? Assume new fluid, not water logged...

2) Does brake fluid get "damaged" when it boils over? If you just let the car cool off, are you back to normal? Again, asssuming the brake fluid is fresh...

1) flush the system
2) yes, once boiled flush it w/ new hopefully w/ a higher wet boiling point.

[KTL]

Originally Posted by Trackrash

Ti pads? Source?

Paragon Products/Racer's Edge or Seine Systems has the Ti shields that are cut to the shape of the 930 pad backing plate

Seine Systems is actually Sherwood Lee (911pcars) here on the forums

Seine Systems > Ti Brake Shield
Seine Systems > Ti Brake Shield
Seine Systems > Order Products

Racers Edge Porsche Suspension
Racer's Edge -- Racer's Edge Titanium brake pad backing plates

[RichardNew]

What is that red area on the brake rotor?

The red area is the temperature sensing paint. You can also use the temperature strips on your calipers



You probably don't need the T1 Brake Shields. The expensive fluid really isn't all that expensive when you consider what you spend for a day at the track.

The single biggest problem is old moisture laden brake fluid. Water boils at 212-degrees. Then your pedal drops to the floor.

You should do a complete brake flush with brand new fluid before you go on the track. Just think of it as part of the preparation.

Richard Newton
How to Choose a Brake Pad

[KTL]

Those crappy sliding calipers need more assistance than a temperature strip. Sorry but I just plain hate sliding calipers. Just a crappy design in so many ways. Flexy, pads fit like crap, various points of potential binding, and so on. Sort of shameful that they've proliferated the brake industry for so long now.

My experience with the SC & Carrera cars is pretty telling in that after a number of track days, the calipers can puke themselves of fluid with pretty much no warning, just sitting in the garage cold. The Ti shields pay for themselves pretty quickly when you consider how much fluid some people use up by bleeding brakes all the time, plus they provide an alternate means of cooling the brakes w/out actually requiring the use of air cooling ducts.

Or another way to look at it is why not treat the heat issue near the source, by blocking it, versus accepting it into the fluid and treating the heat issue with a more heat resistant fluid? Because while the fluid may have a higher boiling point, that still doesn't address the heat attacking the seals.

[Bill Verburg]

Here's what happens to brake fluid from exposure to atmosphere, doesn't take long too go from dry to wet

[RichardNew]

KTL - You want better calipers? Here you go.



Richard Newton
Brake Pad Selection