Brake Fluid Life

[mxz900]

Just curious, when brake fluid heats up from hard braking is the heat in the fluid being absorbed from the rotors, calipers and pads alone or is there also significant heat generated from the immense pressure being put on the fluid? If it is primarily from the brakes themselves is it logical to assume that the heat buildup in the fluid is primarily right at the last couple feet of brake line?

If you took the temp of your fluid in the reservoir after a hard race on a track would it be considerably less than that near the brakes (mostly heated from the engine)? If so, does the fluid ever circulate itself within the lines or when it brakes down from heat and use is it possible that the fluid in the reservoir likely still has it's original properties (or at least much closer to original quality than that near the brakes)? And no, I'm not looking to recycle any fluid, or do a half-a** brake job, just curious how it all operates!

 

[dave6666]

The pressure on the fluid is not really immense. Way higher than a car tire...? Yes, at 1000 psi it certainly is, but compared to a waterjet at 50,000 psi, certainly not. And so on. Most of the heat comes from heat transfer through the components and the ambient surrounding.

I think Snake Oyl has a fluid circulating system. Given the proportions of the brake system - long runs of small diameter tubing - convection circulation from one end of the car to another is not your savior.

 

[GTS Dean]

Most brake reservoirs don't seal tightly enough to keep all water vapor out. Through heat and cooling cycles, water may condense inside the reservoir, settle to the bottom and work its way by gravity to the calipers - usually near the lowest point in the system. Rotors & pads see the highest friction & heat loads. Radiation and conduction heat up the calipers and pistons well above the boiling point of water and even under the extreme pressures in the closed brake system, the working fluid containing water will boil. Convection will eventually mix moisture throughout the system and turn the fluid dark. There are millions upon millions of vehicles out there that have NEVER had their brake fluid changed. Fortunately, most folks don't put the kind of heat load into the system that it causes problems.

A Viper without ABS contains less than 1 pint of fluid volume and a complete flush can be accomplished with one bottle, if you know what you're doing.

 

[sniper1]

The pressure on the fluid is not really immense. Way higher than a car tire...? Yes, at 1000 psi it certainly is, but compared to a waterjet at 50,000 psi, certainly not. And so on. Most of the heat comes from heat transfer through the components and the ambient surrounding.

I think Snake Oyl has a fluid circulating system. Given the proportions of the brake system - long runs of small diameter tubing - convection circulation from one end of the car to another is not your savior.

Most brake reservoirs don't seal tightly enough to keep all water vapor out. Through heat and cooling cycles, water may condense inside the reservoir, settle to the bottom and work its way by gravity to the calipers - usually near the lowest point in the system. Rotors & pads see the highest friction & heat loads. Radiation and conduction heat up the calipers and pistons well above the boiling point of water and even under the extreme pressures in the closed brake system, the working fluid containing water will boil. Convection will eventually mix moisture throughout the system and turn the fluid dark. There are millions upon millions of vehicles out there that have NEVER had their brake fluid changed. Fortunately, most folks don't put the kind of heat load into the system that it causes problems.

A Viper without ABS contains less than 1 pint of fluid volume and a complete flush can be accomplished with one bottle, if you know what you're doing.

What these guys said !!!

 

[GTS Bruce]

I would do a flush and start with better fluid. Motul 600 at a minimum or castrol SRF. Much higher boiling points dry and wet(castrol srf). I started with castrol srf but recently have been using motul with no problems. Bruce

 

[Viper X]

mxz900,

Good responses above. Most of us that track our cars change our brake pads pretty regularly to keep them thick enough so that they don't transfer too much heat. A thinner bad will transfer more heat and larger, heavier rotors will retain more heat longer.

We typically vent at least our front brakes with 3 or 4 inch hoses directing cooling air onto them from the front of the car.

We go to "Aero Rotors" with aluminum hats in most cases that help move air through the rotor's vanes, are lighter and cool quicker.

We use Motul RBF 600 or better brake fluid and change the fluid after every event or two as moisture accumulates pretty quickly during hard usage (like the race track).

Finally, with some driving experience, our driving improves and we brake less but harder for shorter periods, which generates less heat.

Hope this helps.

Dan

 

[mxz900]

Great info everyone. Thanks for the insight. I do use Motul 600 and will be changing it more frequently now. Good to know how quickly this can become vapor soaked though (1-2 races). I admit I have waited longer than that in the past. I will definitely keep an eye on my pads as it makes sense that a worn pad will transfer more heat as there is not as much surface/volume. What are you all using for directing more air to your rotors? I have a gen III which has the factory air dams, but was thinking of trying to make something that I could put in place of the fog lamps on back to the rotors. Anyone make a bolt in air dam for this application or will I have to fab something up?

 

[Viper X]

mxz900,

Call Jon B at Parts Rack and ask him for the "Cone" cooling kit. Very slick - easy install. It hooks up to your factory air intakes and directs air at your front brake calipers / rotors.

Dan