Compression Check: Testing and Inspection

Compression, Checking

• With this engine, the static compression test requires a significant amount of work. Therefore it is recommended to check idle stabilization control before disassembly. Refer to vehicle diagnosis, testing and information system VAS 5051 or VAS 5052 "Guided Fault Finding; Repair Group 15; partial systems, boundary conditions". Only if one or more cylinder(s) is/are noticeable at this point is the compression test warranted.

Special tools, testers and auxiliary items required

• Torque Wrench (5-50 Nm) (V.A.G 1331)

• Adapter for VAG 1323A (V.A.G 1381/12)

• Compression Tester (V.A.G 1763)

• Sealing Tool (T10247) (Vehicles with engine code BKW)

• Connecting Hose (VAS 6278) (Vehicles with engine code BKW)

Test Conditions:

• Engine oil temperature a min. 30 °C (86 °F).

• Ignition turned off

Test Sequence:

- Drain the coolant. Refer to => [ Draining and Filling ] Draining and Filling.

Vehicles with Engine Code BKW:

- Remove the fuel filter. Refer to => [ Fuel Filter ] Removal and Replacement.

- Seal the connection for the fuel hoses using the sealing tool (T10247).






- Connect the fuel supply line - A - using the connecting hose (VAS 6278) to the fuel return line - B -.






Vehicles with Engine Code BWF:

- Remove the bypass flap with cooler for Exhaust Gas Recirculation (EGR). Refer to => [ Bypass Flap with Cooler for EGR ] Bypass Flap with Cooler for EGR.

Continuation for all Vehicles:

- Remove the upper oil filter housing. Refer to => [ Oil Filter Housing Overview ] Description and Operation.

- Remove the glow plugs, refer to => [ Ceramic Sheathed Element Glow Plugs ] Service and Repair.

- Remove the right plenum chamber cover - D -.






- Disconnect the small connectors from the Engine Control Modules (ECM).

• By disconnecting the small harness connectors for the ECM the engine is prevented from starting up even though the starter is turning. If any Diagnostic Trouble Codes (DTCs) are stored in the DTC memory during the starting procedure, it is necessary to check and erase (if required) the DTC memory.

• After the compression test, check the DTC memory. Refer to => [ Engine Control Module DTC Memory, Checking and Erasing ] Scan Tool Testing and Procedures.

- Install the adapter for VAG 1323A (V.A.G 1381/12) in place of the glow plug at the cylinder to be tested.






- Install the upper oil filter housing. Refer to => [ Oil Filter Housing Overview ] Description and Operation.

- Check the compression pressure using the compression tester (V.A.G 1763).

• Using the compression tester, refer to the operating instructions.

- Operate the starter until the tester shows no further pressure increase.

Compression Pressure:

• New: 25..0.31 bar pressure

• Wear limit: 19 bar pressure

• Permissible difference between all cylinders: 5 bar

- Install the glow plugs. Refer to => [ Ceramic Sheathed Element Glow Plugs ] Service and Repair.

- Fill the coolant. Refer to => [ Draining and Filling ] Draining and Filling.

- After all cylinders have been checked and the engine has been completely assembled, check the DTC memory and erase it if necessary. Refer to => [ Engine Control Module DTC Memory, Checking and Erasing ] Scan Tool Testing and Procedures.