The vacuum required for the brake booster to operate is created by a vacuum pump driven by the front end of the engine camshaft.
This is because a turbocharged diesel engine does not have the vacuum in the intake manifold that is used to operate the vacuum booster on cars with gasoline engines.
The cylinder head has a direct splined connection between the camshaft and the vacuum pump drive.
The vacuum pump does not require synchronization with the engine.
The vacuum is created by a blade mounted on the pump rotor.
The rotor is located in the pump body and is connected to the pump shaft.
Lubricant is supplied to the pump under pressure through an oil channel in the cylinder head.
The lubricating oil drains through the bottom of the pump into crankcase.
To prevent oil from entering the vehicle's vacuum lines, a check ball is installed in the vacuum nipple of the pump.
The pump is designed to maintain a minimum pressure of - 45 kPa in idle mode.
The vacuum pump, vacuum reservoir and brake booster are connected via hoses.
The vacuum reservoir increases the volumetric performance of the system.
Reasons for replacing the vacuum pump:
- the vacuum pump drive is damaged, the vacuum pump is worn out or damaged.
To check the vacuum pump, disconnect the vacuum pump hose.
Connect a pressure/vacuum gauge (Part Number 3164491) to the vacuum fitting on the pump.
Start the engine. Let the engine idle for 1 minute to create the required vacuum in the system.
The vacuum gauge must be designed to measure pressures of at least -45 kPa to be able to judge the operation of the pump.
If this minimum vacuum level cannot be achieved, the vacuum pump must be replaced.
The design of the vacuum pump is quite complex, its repair requires special tools and equipment, so if the pump fails, replace it as an assembly.
Loosen the clamp securing the hose to the vacuum nipple pump
Disconnect the hose from the pump
Unscrew the rear bolt securing the vacuum pump
Unscrew the two front bolts securing the vacuum pump to the cylinder head
Removing the pump
Removing the gasket
Install the pump in reverse order.