Brake trouble What is the “vapor lock phenomenon”?
2013 bus accident caused by vapor lock phenomenon
The vapor lock phenomenon is a phenomenon in which when the friction brake of an automobile overheats, the brake fluid that transmits the braking force boils and air bubbles are generated in the brake pipe due to vapor, so that the brake does not work at all. It means that.
As you can see in the video above, it is a terrifying phenomenon that can lead to casualties in some cases, so let’s learn the causes and countermeasures in this article.
There is a similar phenomenon called “fade phenomenon”, but this is a phenomenon in which the friction material of the friction brake is heated, the coefficient of friction decreases, and the brake does not work.
Fading is a phenomenon that occurs before the vapor lock phenomenon and is closely related to the vapor lock phenomenon.
For more information on fading, please check the link below.
The role of brake fluid
Brake fluid is one of the important components of an automobile that has the role of hydraulically (hydraulic) transmitting the force of pressing the brake pedal to the brake body.
Formerly called brake fluid.
When this brake fluid boils, air bubbles are generated in the brake piping, and all the force of pressing the brake pedal is used to crush the air bubbles, so the brakes do not work.
Under what circumstances does the “vapor lock phenomenon” occur?
Be careful downhill!
The vapor lock phenomenon occurs when you continue to descend long slopes relying solely on friction brakes.
First, as a preliminary step, fading occurs due to overheating of the friction brake, and the braking effect deteriorates.
If you continue to use the friction brake, the heat of the entire brake system will continue to rise, and eventually the brake fluid will boil, causing the vapor lock phenomenon.
Be careful of deterioration of brake fluid!
Another cause of the vapor lock phenomenon is deterioration of brake fluid.
Glycol-based brake fluid used in general automobiles has high hygroscopicity, and its boiling point drops significantly when it contains water.
Therefore, the brake fluid that has been used for a long time is prone to the vapor lock phenomenon, and the air bubbles are hard to disappear, so the braking force does not recover.