Checking Pressure Loss Of Cylinders

WARNING: This page is about a different variant/trim than selected.

Information

Pressure of between 6 and 12 bar is required for carrying out the pressure loss test.
Start the test at cylinder 1 and continue according to firing order (1 - 4 - 3 - 2).

The test is described using the > VAS 522 001 - Pressure loss tester .

WARNING: Engine can turn without control (the crankshaft can turn because of the pressure in the cylinder).

Danger of crushing (injury)
Tools can become jammed (material damage)

The piston must be exactly at top dead centre (TDC) position (secure the crankshaft).

→ Do not touch any belt drive components when building up pressure.
→ Do not insert any tools on the crankshaft belt pulley.

Set the piston position (ignition TDC) and connect test tools.

1.1 > V.A.G 1763/9 - Porsche Adapter Set for Compression Tester-1- for spark plug thread M12 x 1.5 (1763/9-1) must be screwed in and tightened hand-tight. Connect dead-centre position gauge -2- .

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Checking piston position using dead-centre position gauge (shown on 991 engine)

1.2 Turn the crankshaft clockwise at the vibration damper as far as the TDC marking of cylinder 1 using > 9773 - turning device .
1.3 Determine the piston position (ignition TDC) of the cylinder to be checked using the dead-centre position gauge.
1. 1.3.1 Piston position of the cylinder to be checked is correct:
  Continue with Step 1.4 (Fix vibration damper in place).
2. 1.3.2 Piston position of the cylinder to be checked is incorrect (overlap):
  Continue to turn the crankshaft 360° clockwise at the vibration damper using turning device.

1.4 Fix vibration damper -1- in place with > 9595/1 - locating pin-4- .

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Disconnecting vibration damper

1.5 Remove the dead-centre position gauge.

Adjust pressure gauge -1- on the tester.
1. 2.1 Connect the compressed air hose -2- to the pressure gauge.
2. 2.2 Connect the compressed air hose to the compressed air system.
3. 2.3 Pull and turn the pressure-regulating valve -3- until the pointer on the pressure loss tester shows 23% -arrow- .
4. 2.4 Lock the pressure-regulating valve. Disconnect compressed air hose.
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Setting the pressure gauge
Connect pressure gauge -1- to the adapter -3- .
1. 3.1 Secure the pressure gauge with a tie-wrap -2- and connect the test hose to the adapter -arrow- .
2. 3.2 Connect the compressed air hose to the pressure gauge.
Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Connecting pressure gauge to adapter (shown on installed engine on Carrera in this case)
Check the pressure loss.
1. 4.1 The pointer on the pressure gauge must move within the green area (0-25 %).
  A loss in pressure of more than 25 % is no longer acceptable and the source of the problem must be found!
2. 4.2 Pressure loss within tolerance range:
  1. 4.2.1 Check the pressure loss on the next cylinder in the same way as for cylinder 1.
    Firing order: 1 - 4 - 3- 2
3. 4.3 Pressure loss not within tolerance range:
  1. 4.3.1 Locate the leak by listening for sounds of escaping air.
    The following areas can be checked:
    
    Intake manifolds (checking intake valves)
    
    Exhaust manifolds and exhaust pipes (checking outlet valves)
    
    Positive crankcase ventilation and oil filler neck (checking piston rings)
    
    Coolant filler neck and spark plug bore of adjacent cylinder (checking cylinder head gasket)
  2. 4.3.2 Then, continue checking the next cylinder in the same way as for cylinder 1.
Remove the turning device from the vibration damper.