Bleeding brakes: Impossible due to system design??

Joined
Dec 23, 2006
Messages
10,335
Location
Canuck - moved to —> California —> Texas —> ???
Emergency braking doesn’t have much to do with moisture level. Fluid cannot reach such heat levels from one hard stop.
But several braking attempts going downhill in the mountains could influence brake performance especially if emergency attempt is made after braking harder several times.
Wet boiling point of brake fluid is measured at 3.4%. That is not tall order and average DOT3 has wet boiling point below 300f. Prestone Synthetic DOT3 has wet boiling point 284f. 5-10yrs old brake fluid is well below that.

You’re right, mountain driving can test even a properly maintained system if one is not careful.

But emergency braking and I’m talking from highway speeds of 70-80mph (should’ve said that in my original post) for sure can expose a weak and under-maintained system as well.

Most situations involve already warmed up brakes from normal driving or stop and go traffic. It doesn’t take much to increase the temperature from there especially at the calipers.

I’m not talking about the pedal going to the floor suddenly, but a gradual decline in braking performance. Something that is not really noticeable in everyday driving.
And an increase of several feet of braking would not really be noticeable, but can definitely mean either stopping on time or hitting whatever is in front of you. But if there is no outright failure, nobody will even question the brakes.
 
Last edited:

Pew

Joined
Mar 12, 2018
Messages
2,276
Location
IL
How about law enforcement vehicles involved in chase where the officer literally left foots the brake and turns the rotors blue due to the extreme braking heat? I’ve seen brake rotors cooked and cracked because of it but yet no moisture or air in the system, ever. I guess it’s because I’m from the south where it’s hotter than hell’s back log all summer… Thanks again!

Most heat in the braking system is contained in the pads and rotors but some does transfer over into the brake fluid. Cracked rotors in their case could be a combination of cheap manufacturing, uneven cooling, activation of the ABS, and improper warmup/cooldown. Low boiling point in these cases may not rear their ugly heads since there were other points of failure.
 
Joined
Mar 8, 2012
Messages
16,991
Location
Colorado Springs
Most heat in the braking system is contained in the pads and rotors but some does transfer over into the brake fluid. Cracked rotors in their case could be a combination of cheap manufacturing, uneven cooling, activation of the ABS, and improper warmup/cooldown. Low boiling point in these cases may not rear their ugly heads since there were other points of failure.
LEO specd. vehicles have same brakes as regular. There are some changes to body possibly for better cooling, but emphasis is on crash survival.
HEMI chargers in EL Paso county Sheriff dept. here and CSPD run on 17” wheels. For vehicle like that to have 17” wheel means smaller rotors and they are heavy. Also, not very well designed steel wheels from cooling perspective add to problems.
They constantly have fade issues. Putting better components requires more money. Money that these departments don’t have or would rather spend on hiring or retention.
 
  • Like
Reactions: Pew
Top