Over heating brakes and padel fade?

[SHOZ]

What happened is your pads overheated and gave up the ghost. When you get the calipers too hot and there is water in the fluid (from being old stuff) then you boil the fluid.

Over heating the pads will deposit material on the rotors and eventually cause wobbling when braking and most people assume warped rotors.

Boiling the fluid will make the pedal soft and keep it that way until the fluid is flushed removing the air (caused by the boiling) and contaminated fluid which caused the problem in the first place.

Bottom line, get better pads and flush the brake fluid when you flush the cooling system every two years.

 

[labman]

What do you mean the brake pedal faded? Did you have a solid pedal that no matter how hard you pushed, you didn't stop? That is caused by organic boiling out of the pads or shoes. They will take a limited amount of that and be OK once they cooled down. Even badly glazed ones may be usable if removed and sanded. Horrible burned, wire smell.

Much less common, is to actually heat the fluid up until it vaporizes when you let off. Reapply, and the pedal goes to the floor. Sweet, antifreeze like smell.

 

[obbop]

Brake too much.... create heat. Lots of heat.

Heat makes matter expand. Heat transfers: pads/disc or drum to the calipers to the axle to the frame to the sheetmetal..... heat transferring everywhere!!!!!!

Expansion!!!!!!!!!!! GROWS!!!!! BIGGER & BIGGER!!!!

Until your conveyance has expanded to immense proportions!!!!

With all that weight no wonder the brakes don't work as well!!!!!

Stop braking and cooling commences. Contraction begins. Shrinkage. Back to original size.

Yep.

 

[Draftmaster3]

I know if you over heat your brakes the brake padel will be soft or fade, the other day we was at work, and one of our workers got hurt and we was working back on a long winding one line black top road,so we got him in the truck ( 97 chevy 1/2 ton 4/4 vortec 350 ) i gave it h""" and in no time the padel was fadeing very badd, but we made it to the doc. fine, and the brakes after cooling off work fine, my ? is why does this happen is brake fluid over heating or what , like i said i know this is normal for this to happen when you get the brakes hot, I was just wondering why it happens, thanks guys ( by the way he is fine )

 

[Quest]

Brake fade typically caused by 3 things:

(a) stuck/seized brake calipers/cylinders and the brake pads are constantly in contact with the friction disc/drums whenever the vehicle in motion.

(b) brake fluid too old--brake fluid has a dry and wet boiling point and as the brake fluid ages, moisture accumulates in the fluid causing a significant drop in boiling point. The lower the boiling point, the sooner you experience brake fade.

(c)inappropriate brake fluid specs: if it calls for DOT3, use DOT3! If DOT4, use DOT4!

 

[John K]

Driving with the emergency brake on will do it in a hurry. Just for curiosity, I googled for brake fluid boiling points. Like Quest said, there is a lot of difference in wet/dry BP.
DOT 3 - 401F / 284F
DOT 4 - 446F / 311F 1% water - 369F 2% water 320F
DOT 5 - > 500F

SHOZ - fyi air is not created when brake fluid is overheated, it is vaporized brake fluid, when it cools, it is liquid brake fluid.

When the brakes overheat it takes more and more force to get any braking, when the fluid boils the pedal goes to the floor as the vaporized fluid is compressible.

 

[unDummy]

Bleed the brakes minimally yearly.
And, at your next brake job, by the best pads/shoes you can get.
Also, never turn rotors/drums. Just buy new ones.

 

[mechtech]

Do you have rear drum brakes? They will expand a lot when hot, and the pedal will go down considerably.

 

[Sid]

Try better brake pads and better fluid.

quote:

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Also, never turn rotors/drums. Just buy new ones.

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Why's that? Theirs plenty of people that shave their rotors and put on new brake pads successfully.

 

[Dark Jedi]

quote:

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Why's that? Theirs plenty of people that shave their rotors and put on new brake pads successfully.

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because your making the walls thinner and will make them heat up twice as quick

 

[bulwnkl]

But they also cool twice as quickly. Even road racers turn rotors (depending upon other factors)...

 

[ChrisW]

and they will distort twice as fast from faster than normal thermal changes.

the more metal the rotor has, the more heatsinking ability it has.

When my rotors are $13 a pop at autozone ($22 for the 'better' grade), why bother to turn them? Many SCCA IT and NASA HC racers use autozone rotors with great sucess, mine are working just fine with hawk HPS pads and valvoline fluid on my 94 civic. Going to upgrade to SS lines and ATE super blue tonight.

 

[Big Jim]

The reason that there are minimum thickness specs for rotors and maximum diameter specs for drums is that there are designed in limits to how much metal can be removed and the rotors or drums still function as designed.

Actually, rotors that have been in use for a while and gone through many heating and cooling cycles and lightly machined can be a more stable rotor than a new "green" one.

 

[mechtech]

All things considered, new rotors are better than cutting old ones 9 out of 10 times.

 

[Sid]

I don't know. If the guys not boiling his fluid (which it sounds like he is) and he has good quality brake pads (which he may not) he shouldn't have much problems. But I agree if rotors are really that cheap for some people I would just get new rotors and give the old ones to the friendly mexicans that collect metal. (Before anyone says anything, all of them really are mexican and friendly.)