Boost Pressure System, Leak Checking

Boost pressure system, leak checking

Note: By using leak tester tool VAG 1681, Test A will completely check the inlet air system for leakage. The following tests are performed with the engine not running.




Test A
If there is still leakage after performing Test A
- perform Test B


Test A leak-checks the following:
- G-charger including silencer
- connecting hoses between silencer and intercooler
- connecting hoses between intercooler (with CO potentiometer G 74) and by-pass
- by-pass tube between G-charger and by-pass
- connecting hose to carbon canister shut-off valve
- throttle
- intake manifold
- fuel injector sealing at seat






- remove camshaft drive belt cover from above engine
A: position crankshaft at TDC for cylinder 1.
B: camshaft cover marking must be between dots on cam gear.
- note position of camshaft gear dots
- turn back camshaft gear approx. 3 teeth by turning crankshaft counterclockwise




- remove crankcase ventilation hose from pressure regulator valve and seal off using adaptor VAG 1687/4
- tighten hose to adaptor using two hose clamps 1




- remove intake air hose flange from G-charger
- install adaptor VAG 1687/2





- close valves 2, 3, 4 on VAG 1687 leak tester, drain viewing glass if necessary using drain screw 6
- connect shop air 1 to VAG 1687 leak tester
- connect pressure hose 5 to tester using adaptor VAG 1687/2
- open valve 3
- adjust pressure on valve 2 to 0.9 bar
- cap pushed upwards

- open valve 4 until the boost pressure circuit (air path) is pressurized
- regulate using valve 2 until 0.9 bar pressure is obtained

- close valve 3 and observe pressure drop
- pressure build-up must not exceed 0.9 bar

- observe pressure after 30 seconds
- pressure must not be less than 0.3 bar

If YES
-determine source of leak by listening, feeling or by applying a commercial leak detector spray

Note: A slight air leak near the top toothed gear of the G-charger does not affect boost pressure. This area is not connected to the boost system when the engine is running.

- release the applied pressure before removing the adaptor by removing the coupling from adaptor VAG 1687/2






Test B

Test B leak-checks the following.
- G-charger with silencer
- connecting hoses between silencer and intercooler
- connecting hoses between intercooler (with CO potentiometer G 74) and throttle body




- A: disconnect by-pass tube at C-charger and install adaptor VAG 1687/1
- B: disconnect intercooler hose from throttle body

- plug off hose opening using adaptor VAG 1687/3
- tighten hose to adaptor using hose clamp





- close valves 2, 3, and 4 on leak tester VAG 1687
- connect air pressure hose 5 to adaptor VAG 1687/2
- open valve 3
- adjust pressure on valve 2 to 0.9 bar
- with cap pushed upwards

- open valve 4 until the boost pressure circuit (air path) is pressurized
- regulate using valve 2 until 0.9 bar pressure is obtained

- close valve 3 and observe pressure drop
- pressure build-up must not exceed 0.9 bar

- observe pressure after 40 seconds
- pressure must not be less than 0.3 bar

If YES
- determine source of leak by listening, feeling or by applying a commercial leak detector spray
- release the applied pressure before removing the adaptor by removing the coupling from adaptor VAG 1687/2
- perform Test A to check for leakage