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Car Braking System
As everyone knows, the only task of brake system is to stop a vehicle as per driver’s needs. In the older models
of Indian cars there were only conventional drum-shoe arrangements in the wheel unit. It did not have any need to have
power brakes to assist as drum brakes provide naturally some of their own power. But in almost 90% of the modern cars
there are only power brakes (at least on the front wheels) as they use disc-caliper arrangements in the wheel unit. In few
of them, Anti Lock Braking System (ABS) is also used for special safety purpose. Here, we will have a very brief idea on
the above.In power brake system there are three very essential main components without which power brakes cannot
work at all. The first is, Vacuum Booster (this characterizes a power brake). Under the bonnet, a black, comparatively
bigger, cylindrical vacuum booster is there at the back of the engine and in the driver’s side. It uses vacuum from
the engine to multiply the force, the driver’s foot applies on it through the brake pedal, by a particular amount.
There is also a check valve, attached from outside of the vacuum booster. It is a one-way-valve causing air only to be
sucked out of the cylinder through vacuum hose. In case of gasoline-powered engine, the vacuum is created in the
booster by the engine itself. But, as a diesel engine does not produce any vacuum, a separate vacuum pump is
necessary to create vacuum in he brake-booster. As the driver hits the brake pedal, the pistons of master-cylinder also
gets pushed in by a rod, attached with the brake pedal passing through the vacuum booster. As brake pedal is pressed,
a diaphragm allows air to be sucked into the booster, as vacuum was previously created by engine in the both side of the
diaphragm. This makes pressing the brake pedal much easier for the driver. Then after completion of this above again
vacuum is created within the booster in the same way.The next important component is Master Cylinder. In most of the
modern Indian road cars the braking system has been divided into two circuits, each operating over two wheels. If any
kind of failure, like fluid leakage, occurs in any of the circuits then the other one will be able to stop the vehicle (though it
will consume more effort) as per requirement. Master cylinder is just after the vacuum booster toward the front of the car.
Over the master cylinder there is a plastic tank connected with an electronic sensor. The plastic tank acts as storage of
brake fluid and the electronic sensor helps to glow the warning light on the dash when the fluid level gets lowered.Within
Master Cylinder (for four wheel braking) there are two pistons (primary and secondary), connected with each other with
the help of spring, for the two brake circuits. Also there are two reservoirs, primary and secondary, for the storage of
brake fluid. When the first cylinder is pressed by the driver with the aid of brake pedal the second piston also gets
pressed with the same pressure. This helps to stop front as well the rear wheel with the same force.Third component is
combination valve. This device is in most of the cars having front disc brakes and rear drum brake. It consists of three
parts- The metering valve, The pressure differential switch, The proportioning valve.The disc brake caliper pad is
normally in contact with the disc. And the brake shoes are normally pulled out of the drum inner surface. So disc brake
calipers are in a position to engage the disc before the shoes engage the drums. Metering valve compensates this by
engaging the drum brake before the discs.Pressure differential switch, an electronic device, alerts driver if there is any
leakage in either of the brake circuit or any difference in pressure is detected between the two brake
circuits.Proportioning valve’s only task is to reduce the braking force on the rear wheel. It generally reduces the
braking force by 30%. As most of the weight is shifted towards the front side of the car while braking, the rear wheel must
be applied a lower braking force to avoid locking and hence skidding. Proportioning valve does this job not to allow more
than 70% of the total applied force to the rear wheel. ABS: Stopping a vehicle all on a sudden becomes very much
challenging. There is a possibility of skidding. But with the aid of Anti-lock Braking System this job has made this job
much safer. The efficiency of an average driver (driving a car with ABS) can be enhanced by as much as they can even
challenge a professional rally driver (driving a car with no ABS) in case of stopping the vehicles on slippery surface. The
working principle of ABS is not too complicated. Hope, we all know a skidding-wheel has less traction (ability to hold the
ground) than a non-skidding one. Anti-lock Braking System’s main task is this, i.e. to keep a wheel from locking
up and hence skidding while braking. This helps the driver in two distinct ways - Allows minimum braking distance
&Allows driver to steer even while braking. N.B. If a wheel skids over, all the frictions, working between the wheel and
road surface are sliding friction. As a consequence the wheel may slide in any direction. But when there is no skidding,
the wheel tries to roll only to the direction of rolling. As a result of this, if there is no skidding steering is possible.The four
basic components of ABS are-
- Speed sensor: It helps the system to know the speed of the wheel or when it about to lock up.
- Valves: These allow the braking pressure from master cylinder right to the braking device. When it is open brakingpressure
is passed to braking device, when it is closed pressure is blocked and when it opens just for a wing, it suddenly
allows a very little portion of braking pressure.
- Controller: It is nothing but an electronic device or computer. This decides when to open or to close the valves
according to the wheel speed.
- Pump: As pressure is released to the brake there must have some mean to withdraw the pressure. Pump serves this
purpose after braking, when the valves gradually reduces the pressure.Main components of braking system: 1. Brake
pedal, 2. Vacuum booster (for power brake) and Vacuum pump (for diesel engine), 3. Master cylinder, 4. Brake fluid
reservoir, 5. Brake fluid, 6. Combination valve, 7. Brake disc, 8. Brake disc calipers, 9. Brake pad (for disc brake), 10.
Brake drum, 11. Brake shoe (for drum brake), 12. Speed sensor (for ABS), 13. Valves (for ABS), 14. Controller (for ABS),
15. Pump (for ABS), 16. Brake fluid channels etc.Common problems:
- Wearing of brake pad/shoe: The friction material of the brake pad/shoe may wear out after being used for long. As a
result the braking distance may increase. In case of disc brakes, the brake pad has then to be replaced and in case of
drum brakes, this problem may be resolved only by scrapping the brake shoe friction surface (sometimes it claims to be
replaced).
- Wearing of brake disc: The brake disc may also be worn out after the vehicle has traveled a lot. Then also the braking

distance increases.
- Failure of brake fluid channels: Sometimes the braking system may fail due to the leakage or wearing of the brake fluid
channels. In case of this type of failure, the vehicle becomes too difficult to stop while running. This may even cause
accidents. If failure of braking system takes place the brake fluid channels have then to be checked thoroughly.
- Leakage in the master cylinder: Sometimes failure of braking system may take place due to the failure or leakage in
master cylinder. In most of the cases vehicles, with four wheel braking system, are found to be failed by one of the
braking circuits within the master cylinder. Then only the two (either of the front and rear) wheels are found to be helping
to stop the vehicle. The braking distance, as a consequence, increases. While checking the braking system, the master
cylinder should first be checked in case of this type of problems.
- Failure of vacuum booster: Sometimes the vacuum booster is found to leak air inside. Then it becomes too hard to stop
the vehicle. As the vacuum booster provides extra effort by creating vacuum inside it (thus reducing the effort of
driver’s foot), if any air leakage occurs, the booster cannot put that extra effort. As a result the brake pedal
becomes very hard.
- Failure of vacuum pump: If vacuum pump, in case of diesel engine, fails it then becomes unable to create the vacuum
inside the booster. Then also the brake pedal becomes too hard thus making the vehicle to difficult to stop.
- Another common problem is unequal distribution of braking force over all the four wheels of a car. If the braking force is
not effective equally on all the wheels, a tendency to drag the vehicle in either side may occur while braking. As a result,
the car becomes prone to accident.
- The ABS, sometimes, found not to work properly. This may be for the failure of any of the components of the Anti-lock
Braking System. It may happen for the failure of speed sensor, may be for the failure of valves, or pump, or for the
controller. Preventive maintenance:
- Always check for the proper brake fluid level in the brake fluid reservoir, at the proper interval as given in the
owner’s manual.
- After every 5000kms the brake pads and shoes must be checked.
- The brake fluid channels must be checked time to time for any leakage or wearing.
- It is also a very essential thing to check the equality of distribution of braking force over all the four wheels.

Car Maintenance Tips
Maintenance is one of the most essential aspects of ownership. It is also something we really neglect until the vehicle
stops functioning. And then only we go around thinking, what may get wrong? As we buy a car we must take care of its
proper maintenance. This not only ensures the car to deliver optimum performance but also enhances its longevity,
durability, reliability etc. Maintaining a vehicle does not mean only to take care of its most outer coat of painting and
keeping it clean and shiny. Maintenance is a complete look after of the external as well as the internal components of a
vehicle time to time. Yes, its true we have no other way than to take our vehicle to the service station whenever the
maintenance is concerned. But before leaving this entirely to the workshop mechanic, we must do another very essential
task. We must go through the owners manual of our respective car (provided by the manufacturing company of the
concerned vehicle) thoroughly. A complete routine of preventive maintenance of the particular vehicle is given there. If
we follow that routine properly, not only the lifetime of the car is enhanced but also the chances of breakdown in time of
need are reduced by almost 95%. Here, in these following articles we are advising some general preventive
maintenances of a car along with a little knowledge of the concerned part and common problems, generally arise
regarding the same.

 
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