Mechanical Engineering - Automobile Engineering - Discussion


The condition that causes vapour locking in a brake system is

[A]. overheating of the fluid due to frequent brake application
[B]. overcooling of the brakes during high speed driving
[C]. keeping the vehicle without use for an extended period
[D]. an excessively high engine speed on a downhill road

Answer: Option A


No answer description available for this question.

Mallikarjun Sadlapur said: (Feb 23, 2013)  
Although brake fluids are designed to work at extreme temperatures above 250C but still as the age of brake fluids goes on increasing, it starts loosing its properties and hence under high pressure and temperatures developed by applying brakes causes vapour lock.

Md Naim Hossain said: (Mar 21, 2013)  
Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines.

It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult.

The fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

Tarn said: (Nov 7, 2013)  
Its a not a possible. Now a days in the ferrari car has a automatic brakes which work when any vehicle crosses very near to ferrari its brakes automatic work.

Rama Kant Verma said: (Jan 14, 2014)  
The vapour lock may occur because of high temperature in brake system due to any reasons either environmental or brake applications but in rare cases because brake fluid has the quality to withstand very high temperatures, in my career I have not come across any brake fluid vapour lock though it may occur in fuel systems.

Kumaresh said: (Jan 25, 2014)  
Due to continuous application of the brake, the temperature of the brake fluid raised. So in some particular cases the brake fluid vaporizes and causes vapour lock.

Ravi said: (Mar 11, 2014)  
When the brake is applied than break shoes is heated in contact shoes and brake drum to decrease to speed than vapour generated than some fluid also vaporized vapour is locked in drum and shoes.

Raviteja said: (Apr 5, 2014)  
While overheating of brake or disc brake, the molecules in chamber or disturbed and some of ingredients, dust and moisture will disturb the brake pad of vehicle.

This results in the vapour locking or some disturbance which results in anti locking of the brake system.

Saurabh Kedia said: (Apr 15, 2014)  
This is basically related to the brake fluid.

Due to their hygroscopic nature they absorb moisture from atmosphere resulting in decrease in boiling temperature and hence changing the fluid in vapour state. As vapour is highly compressible the brake stops working.

Satish said: (Jul 1, 2014)  
The vapor lock is due to continuous application of brake the liquid will becomes vapor, so that vapor lock will occurs.

Varisaikani said: (Sep 18, 2014)  
There is no chance for vapour lock in brakes, now days the brake liquids are manufactured to withstand HIGH TEMPERATURE and there is no DIRECT contact between the BRAKE OIL and BRAKE SHOES.

So the temperature is created by the pressure is within the temperature limit of the Brake oil.

Maddy said: (Oct 15, 2014)  
If there is a problem of vapor lock in break system.

Can any one tell me how to over come this problem.

Abhilash Dubey said: (Dec 16, 2014)  
Basically Brake Fluid are of mainly three types:

1) Mineral.
2) Glycol.
3) Silicone.

Mainly in all of the automobile Glycol is used as Brake Fluid.

Glycol is Hygroscopic in nature, So it absorb Water from the environment during its life from the Master Cylinder, Rubber Hose etc.

Due to Severe Braking or Continuous Braking the temp of the Fluid Rises and Water will convert into Vapour at 100'C.

Being Compressible in nature it lead to loss in Braking Effect or termed as Vapour lock in Brake System.

Manoj Rana said: (Dec 30, 2014)  
This is a term used when the brake fluid in a vehicle brake system is overheat and loses efficiency.

First we will explain what brake fluids usually consist of there are three main types of brake fluids, Mineral brake fluids, Glycol brake fluids and silicone brake fluids. The GLYCOL brake fluid is most common and used in 99.5% of modern vehicle brake systems.

There can be up to 2 pints of brake fluid used in a vehicle brake system and this is piped around the vehicle using copper or rubber hoses to feed the fluid from the operator to the brake system.

Operating the brake forces the fluid into the master cylinder and then brake calipers or wheel cylinders to actuate the brake.

Sasuke said: (Aug 4, 2015)  
During the life of a vehicle or even a drum of brake fluid sitting on the floor of a workshop things happen to Glycol fluids because they are what we call "Hygroscopic". They absorb water even through the walls of the (would you believe) slightly previous rubber brake hoses and open top on cans or vehicle master cylinders.

This water vapour drawn into the fluid will of course boil at somewhere around 100 degrees (or a little more under Pressure) so any water content in a brake fluid is bad news. It also causes system internal parts to corrode.

Kosoko said: (Dec 14, 2015)  
The Hygroscopic nature of the glycol which is often used in now days modern vehicles can easily absorb water from any available surrounding.

This water so absorbed boils at 100'c (even far away from the fluids temperature). Vapour formed is compressible at high pressure hence making the brake to loss it's effect.

Selvam Cr said: (Feb 19, 2016)  
While fluid goes to boil at a high temperature, it will formed into vapour. The density difference between the fluids causes to vapour locking in braking system.

Akshay said: (Apr 28, 2016)  
These problems are taking place in the hilly area the car does not drive smoothly more time brakes can be held down.

Panjarajad said: (Sep 15, 2016)  
Due to their hygroscopic nature, they absorb moisture from atmosphere resulting in a decrease in boiling temperature and hence changing the fluid in vapour state. As vapour is highly compressible the brake stops working.

Abhishek said: (Oct 1, 2016)  
Is this vapour changes to the liquid state when is cooled so that the brake gets restored to the normal state?

Suraj Parida said: (Oct 11, 2016)  
When we applied brake, brake fluid helps to transmit brake power to the brake shoe. Due to frequent use of brake, temperature of the fluid present in it raises. When fluid temperature get raised above boiling point, it converted into vapor. Vapor is more compressible as compare to fluid resulting in auto locking of brake which may cause accident.

Nityanand Haldar said: (May 26, 2017)  
Please clarify the concept of vapour lock.

Whether it occurs due to temp rise by frequent operation of the system or by hygroscopic nature of brake fluid? Or both?

Rumit Bodhe said: (Jul 13, 2017)  
Most of the braking fluid contains glycol fluid. It is hygroscopic fluid. The conversion of water in the brake fluid to steam when the brakes are heated significantly which causes compressibility in the brake system. This vapour lock leads to increased pedal travel and can result in a significant loss of brake effect.

Govind said: (Feb 17, 2018)  
It is possible when the whole brakes lines are unfilled, with the full filled the brakes lines a small quantity of air is in it because brakes lines have narrow size. To comes out the air from brake line, first filled the brake line, then the end of the brakes lines is slight loss the applied the 3or 4 time the air from the lines comes out. There is no another case locking of vapour or air in brakes lines.

Theophilus Zogblah said: (Apr 21, 2018)  
Brake fluid like many other fluids expands under severe and continuous pressure and this give rise to the formation of vapour due to rise in temperature and the resultant effect is that it make brakes ineffective due to vapour lock.

Ramdev said: (Jul 17, 2018)  
In present-day Cars Vapour Lock in Brake system is a distant possibility, might be in Heavy Commercial vehicles it can happen but not sure.

Konda said: (Feb 6, 2019)  
Brake fluid like many other fluids expands under severe and continuous pressure and this give rise to the formation of vapour due to rise in temperature and the resultant effect is that it make brakes ineffective due to vapour lock.

Vijay said: (Feb 12, 2019)  
Braking generates considerable heat and to resist these high temperatures without boiling, brake fluid is designed with a high boiling point. But brake fluid is also hygroscopic, which means it absorbs water. In any hydraulic brake system, the brake fluid gradually absorbs moisture and this reduces the brake fluid's boiling point. Once this moisture absorption reaches a certain level "under prolonged, hard braking, especially in hot weather or heavy loads " the heat can cause the brake fluid to start to boil, creating gas bubbles. As gas is far more compressible than liquid, the driver will experience no pressure at all on the brake pedal, resulting in total loss of brake power known as vapour lock.

Manoj Kumar Majhi said: (Apr 19, 2019)  
Every brake fluid has designed with his stream temperature absorbing capacity when its crossed then it goes towards vapour then locking system for a break is occur.

Praveen said: (Feb 6, 2020)  
Vapor locking due to air in the system is possible and high temperature.

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