NANO

500

BRAKE SYSTEM

General:

TATA NANO is equipped with a mechanical vacuum

booster to assist driver’s pedal effort. This is achieved

by using vacuum from engine inlet manifold. A

diaphragm is provided between the two shells of the

booster, the difference of pressure on two sides of

diaphragm (one side vacuum and another side

atmospheric pressure) gives mechanical advantage.

This amplifies the driver’s pedal effort while braking.

The unit is connected to the brake pedal and the master

cylinder. The vacuum booster input push rod is

connected to brake pedal while the output push rod

operates the master cylinder. If failure of vacuum

occurs, the two push rods act as a single rod and the

brakes will work in the conventional manner, but more

pedal effort will be required and the fatigue of the driver

will increase.

The booster assembly and TMC assembly are coupled

with the help of fasteners. The meting dimensions of

booster and TMC are factory set

Hence:

1. Do not alter the height of the output rod of the

vacuum booster unit at any stage and ensure

booster out put rod is correctly aligned to the

primary piston bore during assembly of TMC

to the booster.

2. Once the booster assembly is removed from

vehicle, at the time of refitting on vehicle, the

gasket at the mounting face of the booster

should be replaced with a new one.

3. Booster assembly is a non serviceable unit and

it should never be tampered with.

2. Brakes Applied

When the brake pedal is depressed, the input rod

assembly moves forward inside the diaphragm plate

until the control valve closes the vacuum port; at this

stage vacuum is still present on both the sides of the

diaphragm. As the input rod continues to move

forward, the control plunger moves away from the

control valve, opening the atmospheric port, which is

formed between these two parts. Air enters the rear

shell behind the diaphragm and the effect of

atmospheric pressure assisted by the valve rod helps

in pushing the diaphragm plate forward and thus the

output rod actuates the TMC plunger.

Vaccum port

WORKING PRINCIPLE OF VACUUM

BOOSTER

1. Brakes OFF

The diaphragm is fully retracted and is held against

the rear shell by the diaphragm return spring. The input

rod assembly is also fully retracted by the brake pedal

return spring. With the input rod in this position, the

vacuum port is open and the vacuum is applied on

both the sides of the diaphragm.