Coolant: Service and Repair
Draining and filling in coolant
Preliminary work
1. Remove rear underbody panel.
Draining coolant
Information
^ Check Henn coupling O-rings and replace them if necessary.
^ Clean plug connection and coolant hoses before assembly.
^ Coat O-rings and coolant hoses with Kluberplus Gel (Part No. 000.043.205.93).
^ Remove stoppers before fitting the coolant lines and hoses.
Warning
Hot pressurized coolant.
^ Danger of scalding and burning.
-> Only work on the coolant system when the engine is "cool".
-> Wear protective clothes, gloves and goggles.
1. Open cap on the expansion tank -1- and remove it. Set the steel clip on the bleeder valve in a vertical position -2-.
Expansion tank cap for coolant expansion tank
Warning
Hot pressurized coolant.
^ Danger of scalding and burning.
-> Only work on the coolant system when the engine is "cool".
-> Wear protective clothes, gloves and goggles.
Warning
Coolant is corrosive and hazardous to health.
^ Risk of skin and eye irritation.
-> Wear protective gloves and goggles.
-> If you come into contact with coolant, wash off immediately with plenty of warm water.
2. Loosen drain plug (hexagon socket) on the coolant guide tube. Open spring band clamp on supply hose to water pump, remove the hose and unscrew the drain plug. Collect coolant in a clean container. Re-fit the hose and screw on the drain plug with a new sealing ring. -> Tightening torque: 10 Nm (7.5 ftlb.) +5 Nm (+3.5 ftlb.)
Coolant drain plug
Warning
Hot pressurized coolant.
^ Danger of scalding and burning.
-> Only work on the coolant system when the engine is "cool".
-> Wear protective clothes, gloves and goggles.
Warning
Coolant is corrosive and hazardous to health.
^ Risk of skin and eye irritation.
-> Wear protective gloves and goggles.
-> If you come into contact with coolant, wash off immediately with plenty of warm water.
3. Drain off additional coolant by removing the supply hose at the water pump -1-. Collect coolant in a clean container. Re-fit supply hose.
Coolant inlet hose
4. Open supply and return hoses at radiators. Do this by pulling off the spring clips for the two Henn couplings -1- and pulling the hoses away from the coolant pipes -2-. Collect coolant in a clean container.
Insert the clips in the correct position in the connectors and connect the hoses. The connection should audibly snap into place. Check correct positioning once again by pulling on the hoses.
Henn coupling for coolant hose inlet
5. Remove heating hoses on underside of car. Secure the pipes with hose clips and then open the spring band clamps. Remove both hoses and slowly open hose clamps. Allow coolant to drain into a clean container. Clean hoses, stick them back and attach the clips. Check that the hoses are firmly in place.
Unclipping heating hoses
Filling with coolant
Filling coolant (includes bleeding)
Information
The process of filling and bleeding the cooling system continues to be performed using the special tool Radiator filling device 9696.
Information
^ If a vacuum does not build up, there is a leaking valve in the coolant circuit.
^ Deformation of the rubber hoses of the cooling system is normal.
^ When the pressure gauge pointer is in the green area of the display scale, a sufficient vacuum has been built up.
^ After both shutoff valves on the vacuum pressure gauge have been closed and the compressed air supply has been disconnected, the vacuum must not drop. If the vacuum drops within approx. 30 seconds, there is a leak in the coolant circuit.
1. Screw cap adapter for coolant expansion tank (K 22) onto the expansion tank and attach the flexible extension (Fz 100) to the cap.
Adapter K22 on coolant expansion tank
2. Connect the vacuum pressure gauge of the bleeder tool to the flexible extension. When doing so, ensure that both shut-off valves are closed (positioned at 90° to flow direction).
3. Connect the Venturi nozzle to the vacuum pressure gauge.
Venturi nozzle on vacuum pressure gauge
Information
^ The quantity of coolant available should exceed the amount required to fill the system by about two liters in order to prevent air being sucked in.
^ An antifreeze content of -35°C corresponds to a mixture of 50:50 (antifreeze: water).
4. Place a canister with a sufficient amount of coolant and with an antifreeze content of -35°C behind the vehicle near to the expansion tank.
Information
^ The bleeding process is completed more quickly if the canister is positioned at the same height as the coolant reservoir.
5. Push the filler hose of the vacuum pressure gauge -5- onto the canister connection. Draw off the return line -6- of the Venturi nozzle into a second container.
Special canister filling tool
Information
^ A hissing sound after connecting the compressed air supply is usual.
6. Connect compressed air supply to Venturi nozzle.
Compressed air supply on Venturi nozzle
7. Open both shut-off valves on the vacuum pressure gauge until the transparent filler hose has completely filled with coolant.
Shut-off valves open
8. Close the left shut-off valve on the vacuum pressure gauge and allow a vacuum to build up in the coolant circuit.
Left-hand shut-off valve closed
9. When there is sufficient vacuum in the cooling system, close right shut-off valve and then disconnect the compressed air supply.
Vacuum established (pointer in green region)
10. Open the left-hand shut-off valve on the vacuum pressure gauge (right-hand valve closed -Arrow-). The cooling system is then filled.
Left-hand shut-off valve open - right-hand valve (arrow) closed
11. When the cooling system no longer contains a vacuum (vacuum pressure gauge shows zero), i.e. no more coolant is being sucked out of the canister, open right-hand shut-off valve.
12. Then remove the complete filling device 9696 (including cap K 22).
13. If necessary, fill the coolant expansion tank with coolant up to the maximum marking and screw on the cap of the expansion tank (do not tilt).
Reworking
Subsequent work
1. Check coolant line connections and hoses for leaks.
2. Completely install rear underbody panel.
3. Test drive the vehicle. Following the test drive and when the engine is still at operating temperature, accelerate briefly to greater than 6,000 rpm a number of times at idle speed in order to fully ventilate the system.
4. Check the fluid level with the aid of the marks on the expansion tank. If necessary, correct the coolant level after the engine has cooled.