Vacuum tubes
Plastic vacuum tubes connect the brake booster to the vacuum source. Control valves are built into the vacuum tubes. Gasoline models have two built-in check valves that maintain brake booster pressure when the throttle is open and the vacuum pump is not running, and prevent fuel vapor from entering the brake booster. On diesel models, there is one check valve built into the vacuum tube connection to the brake booster that maintains brake booster pressure when the vacuum pump is not working optimally.
Brake booster
The brake booster is installed in the engine compartment on the driver's side, on the engine bulkhead.
The brake booster is a dual diaphragm design with a transmission ratio of 7.0:1. The input rod is connected to the brake pedal. The output rod enters the master piston of the brake master cylinder. The vacuum tube is installed in a sleeve on the front of the housing and connects the brake booster to the intake manifold and electric vacuum pump (for petrol engine models) or engine driven vacuum pump (for diesel models).
Vacuum pump (4.0 l and 4.4 l)
Item name | Spare part number | Description |
1 | - | Anti-vibration mount |
2 | - | pump cover |
3 | - | Vacuum pump inlet |
4 | - | Outlet rubber cover |
5 | - | motor cover |
6 | - | electrical connector |
On gasoline engine models, an electric vacuum pump supplements the main vacuum supply from the engine manifold.
The vacuum pump is mounted on a support bracket in the left front corner of the engine compartment. The two anti-vibration mounts of the vacuum pump are mounted on the studs of the support bracket and secured with nuts.
The vacuum pump is a radial vane pump driven by an electric motor. The pump rotor and vanes are made of self-lubricating carbon-based material. A branch pipe is installed on the pump inlet, designed to connect a vacuum tube from the brake booster. The second pipe with a rubber casing is installed on the outlet of the pump.
The vacuum pump is controlled by the engine control module (ECM), which supplies power to the vacuum pump via the vacuum pump relay in the battery electrical junction box (BJB). The ECM regulates the vacuum pump on time and has built-in overload protection; for example, to prevent excessive continuous operation of the pump, a minimum allowable delay is set between pump starts.
Vacuum pump (diesel engine 2.7 l)
Item name | Spare part number | Description |
1 | - | Vacuum connection (not used) |
2 | - | Vacuum connection of brake booster |
3 | - | Drive unit |
4 | - | Seal |
5 | - | Oil inlet |
6 | - | Oil outlet/vent |
The vacuum pump is installed on diesel models because the intake system does not create enough vacuum for the brake booster to work satisfactorily.
The vacuum pump is a radial vane pump mounted on the rear of the right cylinder head and driven by the exhaust camshaft at half the engine speed. The brake booster vacuum pipe is connected to an elbow on the vacuum pump rim.
The vacuum pump is lubricated and cooled by engine oil supplied to the hole on the front surface of the vacuum pump from the channel in the cylinder head. The oil returns to the cylinder head drain through a vent on the front of the pump. The air taken from the brake booster is fed into the drain channel along with the returned engine oil.
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