When the engine is hot, place a thick rag over the expansion tank before opening the expansion tank to prevent hot fluid and vapors from escaping, which could cause burns. The lid can only be opened when the liquid temperature is below +90°C.
1. Check the coolant level.
2. Check that all hose connections are dry. Wipe them down if necessary.
3. Fit the pressure test tool -1- to the filler pipe on the radiator. Pressurize 1.5 bar with the hand pump of the instrument and wait 2 min.
4. The generated pressure may drop to no more than 0.1 bar within 2 minutes. If the pressure drops further, locate the leak in the system. When the pressure rises, the liquid flows out through the leak. Seal the leak.
5. If the pressure drops without fluid loss, the leak may be in the engine, such as a defective cylinder head gasket or a crack in the housing.
6. If the pressure holds even though there is a loss of coolant while the vehicle is moving, start the engine and let it idle. Pressurize about 1 bar with a hand pump and visually check the radiator. Locate the leak and seal.
7. Stop the engine. Slowly unscrew the connecting element, relieving pressure in the cooling system.
Plug valve check
8. Screw plug -2- onto test tool -1-.
9. Pressurize the hand pump on the tool. The cork must be airtight. The safety valve in the plug should only open when pressure is applied 1.0 bar (Models 320d: 1.4 bar). Otherwise, replace the plug.
10. Create a vacuum in the cork. Under vacuum 0.1 bar the vacuum valve in the radiator cap should open.
11. If there is damage to the rubber ring in the plug, replace it. Screw on the plug.