Engine - Checking the Intake Systems For Leaks
85porsche01Subject:
Checking The Intake Systems For Leaks
Model 911, 911 Turbo, 924 924 Turbo, 928
Group
2
Part Identifier
N/A
Number
8502
April 16, 1985
Past experience has shown that leaks in the Intake System may result in performance problems. These leaks are at times difficult to detect and often overlooked if not diagnosed systematically.
To perform the respective leak tests rationally, a plate can be made (drawing #1) which permits a 100% checkup for leaks on vehicles Type 928, 911 Turbo, and 924 Turbo. A different self-made tool will be used for the 922 and 924 (drawing #3).
Checking the 928 and 911 Turbo
Remove sensor late stop and install sealing plate and seal using the two screw points.
Pressurize system with air to 0.5 bar (7 PSI).
There is no need to seal the exhaust system since the engines usually stop in such a manner that at least 1 valve per cylinder is closed, so that the pressure of approximately 0.5 bar obtained via sealing plate will not be reduced through exhaust system.
With pressure built up, larger leaks can be heard, slight leaks can be made visible by means of a leak detecting spray, which is non flammable and non-toxic, or soapy water.
On all 911 Turbos with flanged air flow meter, a ring of 130 mm diameter together with sealing ring 930.110.122.00 is placed between the sealing plate and the airflow meter (drawing #2).
924 Turbo
The system is also sealed through the air flow meter. Due to the smaller diameter of the air flow meter, the sealing M8 bolt must be removed from the sealing plate, so the plate can be fastened through this hole.
911
The throttle housing is sealed by means of a self-made tool, (see drawing #4), and the rubber boot removed.
Cars equipped with an Auxillary air valve and Regulator, the hose from the rubber boot must be sealed with a round object.
944 and 924
A sawed-off fuel filter 928.110.147.05 is modified with a tubeless valve (drawing 3).
On the 944, this device is installed behind the air flow meter, into the intake hose.
On the 924, this device is installed in the connecting hose in front of the throttle valve. In addition, when installed, the vacuum hose in front of the vacuum booster must be pinched.
Device for pressure testing K-jetronic intake system
911 TURBO, 924 turbo, 928
Testing intake system for leaks:
Self-made tool:
Saw off fuel filter 928.110.147.05 approx. 30 mm behind input end. Press tubeless valve into hollow screw.
This adapter is inserted into connecting hose instead of the air flow meter and is fastened with hose clamp. Establish approx. 0.5 bar pressure in intake system by means of a tire inflator and spray all connections with a leak-detecting spray. The leaking spot will be indicated by bubbles.