Additional force is provided by the reduced pressure from the intake manifold. The brake booster is connected by a hose to the exhaust manifold. When braking, the difference in pressure between the external air pressure and the reduced pressure in the exhaust manifold moves a large elastic diaphragm and additionally presses on the piston in the main brake cylinder. If the engine is not running, the booster cannot develop any (additional) braking force. If the engine suddenly stalls, there is still a small reserve for a certain amount of braking; but then you will have to rely only on the strength of your legs.
The five-cylinder engine has an additional vacuum pump (3), which increases the vacuum in the hose from the intake pipe (1). Thus, it is possible that in the hose from the pump to the brake booster there is always enough force to support the brakes. To prevent the reduced pressure from disappearing, a check valve (2) is installed before the branch to the pump.
Depending on the vehicle's loading condition, the brake force regulator (1) applies more or less pressure to the rear axle wheel cylinders. How much the rear axle is loaded - this information is supplied to the regulator via the connection to the rear axle, which consists of a small spring (2). The illustration on the left shows the brake force regulator for front-wheel drive vehicles, the picture on the right shows the regulator for a four-wheel drive vehicle.
Vacuum pump
To improve braking force maintenance, the engine versions are equipped with an additional vacuum pump driven by the camshaft. Thanks to it, the underpressure in the hoses to the brake booster is increased.
The following engines have this pump:
All cars with 5-cylinder engines. The pump is installed on the left side of the cylinder head.
All cars with 6-cylinder engines. Here it is located behind the right cylinder head (then the vacuum pump is installed only in cars with automatic transmission).
Since 3/92, a jet pump has been installed in cars with 6-cylinder engines and automatic transmission. The mechanical pump has ceased to exist.