11 66 521 Checking function of vacuum system (N55)

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Special tools required:

81 38 2 201 924
2 201 924

IMPORTANT: Note the sequence of the diagnosis instructions in the ISID :
Depending on the fault pattern, the order of operations in the repair instructions may be different from the order of operations in the ISID .

Carry out procedure to check the vacuum system.

Check the function of the vacuum pump:

Press and pull off the lock of the vacuum line (1) (see arrows).

NOTE: This empties the vacuum reservoir, this will always be accompanied by a sucking noise.

Fig 1: Pressing Vacuum Line Lock

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Check suction effect of vacuum pump.

Connect vacuum line (1) and IMIB with special tool (2) 81 38 2 201 924.

Start engine.

Run engine at idle speed.

Follow diagnosis instruction.

Fig 2: Connecting Vacuum Line And IMIB Using Special Tool (81 38 2 201 924)

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Check vacuum reservoir.

Reconnect vacuum line from vacuum pump to the vacuum reservoir.

NOTE: When the IMIB (1) is used the absolute pressure is displayed.

Follow diagnosis instruction.

Fig 3: Identifying IMIB

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Pull off connection (1) at the vacuum reservoir to the exhaust flap.

Pull off connection (2) at the vacuum reservoir to the EPDW (pressure converter).

Fig 4: Identifying Vacuum Reservoir Connections

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Check vacuum reservoir.

Seal connection on vacuum reservoir with sealing cap (1).

Connect vacuum reservoir and IMIB using special tool 81 38 2 201 924.

Follow diagnosis instruction.

Fig 5: Identifying Sealing Cap

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Functional check of exhaust flaps (if installed).

Checking function of exhaust flap (1).

Follow diagnosis instruction.

Illustration: E81.

Fig 6: Identifying Exhaust Flap

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Check suction operation on the exhaust flap.

Pull off the vacuum line to the EPDW at the vacuum reservoir and seal the connection at the vacuum reservoir with sealing cap (1).

Pull off the vacuum line (2) to the exhaust flap and connect to special tool 2 201 924 and vacuum reservoir using T-piece.

NOTE: When the IMIB is used the absolute pressure is displayed.

Fig 7: Checking Suction Operation On Exhaust Flap

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Follow diagnosis instruction.

Leakage test of vacuum line to exhaust flap.

Disconnect vacuum line (1) with pliers (2) as shown in the graphic.

Follow diagnosis instruction.

Fig 8: Disconnecting Vacuum Line Using Pliers

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Check function of wastegate valve.

Initial setting of wastegate linkage (1).

Observe wastegate linkage (1); it must close following activation (arrowed).

Follow diagnosis instruction.

Fig 9: Checking Wastegate Valve Function

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Pressure converter connections

Disconnect vacuum hose at connection (VAC = vacuum reservoir).

Disconnect vacuum hose at connection (OUT= turbocharger vacuum unit).

Fig 10: Identifying Vacuum Hose Connections

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Leakage test of hoses to wastegate valve.

Pull vacuum line off pressure converter plug connection (OUT).

Pull vacuum line off pressure converter plug connection (VAC).

Connect both vacuum lines to special tool 2 201 924 with a T-piece (1).

Follow diagnosis instruction.

Fig 11: Connecting Vacuum Lines To Special Tool (2 201 924) Using T-Piece

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NOTE: Remove all special tools.
Reassemble the vehicle.