brake fade experience

[bill_j_brown]

I was recently a passenger in an accident where a colleague of mine drove his 1990 celica off the road. He told me that the brakes failed and that the peddle felt spongy. This makes sense, because we came down a long hill and could smell the brakes heating up. What doesn't make sense is that after coming down the hill we stopped for 15 mins at a restroom before getting back in the car when the brakes failed after about 500 yards. Also the police and AAA checked the brakes after they towed the car out the next day and told him they work now. It sounds most likely that the brake fluid heated up, but I don't understand why they didn't fail before we stopped. Can anyone tell me how brake fluid can heat up, then get weaker while a car is stopped for 15 minutes, then fail, then recover? Or is it more likely that he just lost control of the vehicle and is trying to cover up? Any suggestions on what I could look for if I get a chance to look at the car? I'm grateful for any response.

Bill

[stepho]

The heat boils the brake fluid.
Brake fluid can be pushed through the brake pipe but the boiled vapour won't push anything (the vapour just compresses itself a little more and raises the heat even more).
This is made worse by the smallest amount of water and brake fluid tends to absord moisture from the air - which is why brake fluid needs to be replaced occasionally.

Any air bubbles also make it very bad all the time - which is why we bleed the brakes of any air bubbles.

It recovered a little bit just after your accident when it cooled down a little.
It then recovered all the way when it cooled down all the way.

- stepho

[Pineapple]

The heat melted the pads which turn them into a nice smooth piece of plastic. At first the pad fade due to melting then after cool down it glaze.

[ShawnM]

You have to keep in mind that the most heat is generated right after you stop and turn off the car. Mostly because there is no air circulation to help cool things down. This type of heat soak can last for quite a while after the car is turned off. It applies to everything from your brakes, engine, transmission, exhaust and so on. Im betting he never had the brake fluid flushed either, which makes things worse since it absorbs moisture over time. Once the fluid completely cools down the brakes will feel normal again.

[bill_j_brown]

Thanks a lot for your time to answer this. The last answer makes a lot of sense. Strange that there aren't standard checks for the brake fluid.