Contents: Petrol engines ↓ Diesel engine ↓
1) Except for the 118 kW (160 hp) engine.
Compression testing allows you to draw conclusions about the condition of the engine. Namely, it allows you to determine whether the valves or pistons are in good condition (piston rings), or they are worn out. In addition, the check shows whether the engine should be replaced or completely overhauled. To check, you need a compression tester, which is offered very inexpensively in specialized stores for gasoline engines.
Note: Diesel engines require a compression tester with an extended measurement range.
The most information is provided by the difference in pressure in individual cylinders. It should not exceed 3.0 bar (for diesel engines 5.0 bar). If one or more cylinders have a pressure that differs from the pressure in other cylinders by more than 3.0 bar (for diesel engines 5.0 bar), this indicates a defect in the valves, wear of the piston rings or cylinder working surfaces. If the wear has reached the limit, the engine must be repaired or replaced.
Petrol engines
The compression test must be performed on a warm engine. The engine temperature must be at least 30°C.
Turn off the ignition.
Engine with injection system: remove the fuel pump relay.
Caution: High voltage wire (central wire, terminal 4) remove from the ignition distributor and connect to the vehicle ground using a suitable auxiliary wire. The auxiliary wire must have the same cross-section as the high-tension wire and have alligator clips at both ends. Do not hold the wire with your hands.
Pull out all spark plug tips. There is a special clamp for this, for example HAZET1849. In this case, grip the tips only by the metal sleeves.
After this, blow out the spark plug recesses in the cylinder head with compressed air and unscrew all the spark plugs with a suitable wrench.
Turn the engine over a couple of times with the starter to flush out carbon deposits and soot from the cylinders.
Attention: shift the gearbox into neutral and apply the handbrake.
Press the compression gauge against the spark plug holes or screw it in according to the service manual.
Ask your assistant to fully depress the gas pedal and hold it with his foot throughout the entire test.
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Turn the engine approximately 8 revolutions until the readings on the instrument scale stop changing.
Check all cylinders in sequence and compare the obtained values with the prescribed ones.
After this, screw in the spark plugs and insert the spark plug wire, see chapter "Ignition system".
Diesel engine
Engines with power from 65 to 80 hp:
Remove the electrical wire from the fuel supply switch at the high pressure fuel pump.
Remove the injectors, see chapter "Diesel engine".
Screw in a compression gauge instead of the injector. At the same time, install the old heat-insulating gasket between the pressure gauge and the cylinder head.
Note: The given compression values are valid only when checking the compression with a VAG-1381 compression tester and the presence of a VAG-1323/2A adapter.
Tighten the injectors to a torque of 70 Nm. Note: Always replace the heat-insulating gasket between the cylinder head and the injector. The recess in the gasket must face upwards when installing. Tighten the fuel lines to a torque of 25 Nm.
Connect the wire to the fuel switch.
Turbocharged diesel engine with 90 and 110 hp.
Disconnect the fuel shut-off valve plug from the high-pressure fuel pump.
Remove the glow plugs, see chapter "Diesel engine".
Screw in the compression gauge instead of the glow plug. At the same time, install the old heat-insulating gasket between the pressure gauge and the cylinder head.
Attention: The given compression values are valid only when checking the compression with the VAG-1763 compression meter and the presence of the VAG-1323/18 adapter.
Check all cylinders in sequence.
Tighten the glow plugs to a torque of 15 Nm.
Connect the electrical wires.
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