1996 AUDI A4 AWM Engine Charge Pressure Leak Test Workshop Manual

21-21

Performing pressure test:

- With outlet hose -1- of VAG 1687 connected to air pressure adapter:
- Attach shop air supply line to previously installed male fitting Page
21
-16
.

CAUTION! - Open valve -3- between regulator valve and gauge.
- Adjust test pressure up to 0.5 bar ( CAUTION below) by turning
regulator valve -2-.
DO NOT pressurize the system above 0.5 bar!Doing so may force oil into the intake system which can damage
the engine.
- Slowly open outlet valve -4- (after gauge) to test hose connections.
- Observe pressure gauge for a drop in pressure.
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21-22

Note:
Some pressure will be lost past the throttle plate.

- Readjust test pressure to 0.5 bar ( CAUTION
above) by turning regulator valve -2-.
- Listen for any very large intake leaks.
If smoke generator was used to fill the system
with smoke:

- Inspect intake system connections for smoke at
leaks.

Note:
An ultrasonic detector may also be used to
detect extremely small leaks where smoke may
not be visible.

- Repair any leaks found.

- Remove tester.

- Remove plug from crankcase ventilation hose.

- Remove air pressure adapter.
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With VAS 5051 diagnostic tool connected:

- Erase DTC memory.
If smoke generator was not used to fill the
system with smoke:

- Apply soapy water solution or equivalent to
intake system connections.
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21-23

Note:
An ultrasonic detector may also be used to
detect extremely small leaks.

- Inspect intake system connections for leaks.

- Repair any leaks found.

- Remove tester.

- Remove plug from crankcase ventilation hose.

- Remove air pressure adapter.
With VAS 5051 diagnostic tool connected:

- Erase DTC memory.
Pa
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21-24

Mechanical air recirculation valve,
checking


Note:

The mechanical air recirculation valve is
upstream of the exhaust turbocharger. It is
opened via vacuum by the recirculating valve
for turbocharger -N249- under conditions of
overrun, idling and partial load. This reduces
the charge pressure upstream of the throttle
valve. A high turbocharger speed is thus
maintained.
Check the air recirculation valve if the engine is
not producing full power, or jerking when the
throttle is opened and closed.

Special tools and equipment

Hand vacuum pump VAG 1390
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21-25

Test sequence

If the air recirculation valve does not open and close as specified, or if the
valve plate does not seal properly when the valve is closed: - Attach vacuum pump VAG 1390 to air recirculation valve.
- Actuate hand vacuum pump.
Air recirculation valve should open -arrow-
- Operate air vent valve on vacuum pump after about 30 seconds.Air recirculation valve should close -arrow-
- Replace air recirculation valve and attach hose connections with hose
clamps.
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21-26


Recirculating valve for turbocharger -
N249-, checking

Special tools and equipment

VAG 1526 A
VAG 1527 B
VAG 1594 A
VAG 1598/31
VAS 5051 with VAS 5051/1
- or
VAG 1551 with VAG 1551/3 A
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21-27

Test requirements:

Vehicle diagnostic, testing and information
system VAS 5051 or VAG 1551 Scan Tool
connected.

Test sequence

Note:
The recirculating valve for turbocharger -N249-
and the wiring connections are monitored by the
engine control module.

- Read Diagnostic Trouble Code (DTC) memory
of engine control module.
If a DTC relating to the recirculating valve for
turbocharger -N249- is displayed:

Note:
The illustration shows bottom view of removed intake line. - Remove hoses of recirculating valve for turbocharger -N249- (-1-). The
electrical connector remains plugged in.
Location: below intake line
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