Cooling System: Testing and Inspection

Cooling System, Checking for Leaks

• Make sure when replacing the expansion tank and for maintenance work that there is always a silicate cartridge in the expansion tank, refer to the Parts Catalog. The silicate cartridge must not be removed.

Special tools, testers and auxiliary items required

• Cooling System Tester (V.A.G 1274 B)

• Adapter (V.A.G 1274/8)

• Adapter (V.A.G 1274/9)

Test Conditions

• The engine is at operating temperature.

Test Sequence


Steam can be released when the cap is removed from the expansion tank. Cover the cap with a cloth and open carefully.

- Remove the coolant expansion tank cap.

- Install the adapter (V.A.G 1274/8) onto the coolant expansion tank.

- Clamp the connection (V.A.G 1274 B/1) on the adapter (V.A.G 1274/8).

- Connect the connection (V.A.G 1274 B/1) to the cooling system tester (V.A.G 1274 B) using the hose provided.






- Generate a positive pressure of approximately 1.0 bar using the hand pump of the cooling system tester.


Risk of scalding! Reduce the pressure before disconnecting the cooling system tester (V.A.G 1274 B) from the connecting hose or connection (V.A.G 1274 B/1). To do this, press the pressure release valve on the cooling system tester (V.A.G 1274 B) until the pressure gauge displays 0.

If the pressure drops:

- Search for a leaking area and repair the malfunction.

Checking the Pressure Relief Valve in the Cap

- Install the cap onto the adapter (V.A.G 1274/9).

- Clamp the connection (V.A.G 1274 B/1) onto the adapter (V.A.G 1274/9).

- Connect the connection (V.A.G 1274 B/1) to the cooling system tester (V.A.G 1274 B) using the hose provided.






- Actuate the hand pump.

• The pressure release valve must open at 1.4 to 1.6 bar.