11 66 521 Checking function of vacuum system (N20)

Special tools required:

31 2 357 800 (previously: 81 38 2 201 924)

Attention!

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 suction effect of vacuum pump.

Detach vacuum line (1) from vacuum reservoir.

Detach vacuum line (2) from exhaust flap.

Fig 1: Identifying Vacuum Lines

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Check suction effect of vacuum pump.

Fit special tool 81 31 2 357 800 (previously: 81 38 2 201 924).

Seal vacuum line from vacuum pump to vacuum reservoir with a suitable plug (1).

Follow diagnosis instruction.

Fig 2: Fitting Special Tool (2 201 924)

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Check vacuum reservoir.

Reconnect vacuum line from vacuum pump to the vacuum reservoir.

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

Follow diagnosis instruction.

Fig 3: Identifying IMIB

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Check vacuum reservoir.

Detach vacuum line (1) from vacuum reservoir.

Seal connection on vacuum reservoir with sealing cap (2).

Follow diagnosis instruction.

Fig 4: Identifying Vacuum Line And Sealing Cap

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Functional check of exhaust flaps.

Check function of exhaust flap (1) on both rear silencers.

Follow diagnosis instruction.

Fig 5: Identifying Exhaust Flap

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Check suction operation on the exhaust flap.

Disconnect vacuum line (1) to exhaust flap at left spring strut dome and reconnect with a T-piece.

Connect special tool 81 31 2 357 800 (previously: 81 38 2 201 924) with T-piece.

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

Fig 6: Connecting Special Tool (2 201 924) With T-Piece

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Follow diagnosis instruction.

Leakage test of hoses to exhaust flaps.

Check leakage test of hoses to exhaust flaps.

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

Follow diagnosis instruction.

Fig 7: Disconnecting Vacuum Line With Pliers

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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 8: Identifying VAC And OUT Vacuum Hose Connections

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Leakage test of hoses to wastegate valve.

Connect vacuum line (1) with vacuum line (2) from vacuum reservoir with a T-piece and special tool 81 31 2 357 800 (previously: 81 38 2 201 924).

Follow diagnosis instruction.

Fig 9: Connecting Vacuum Lines With T-Piece And Special Tool (2 201 924)

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Check function of wastegate capsule.

Check function of linkage.

Follow diagnosis instruction.

Fig 10: Checking Wastegate Capsule Function

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NOTE: Remove all special tools.
Reassemble the vehicle.