Coolant: Service and Repair
WM 193817 Draining and filling coolant (includes bleeding)
Tools
Preliminary work
Information
- Cooling systems with thermal management (controlled thermostats or coolant valves for controlling engine temperature) must be vacuum-filled.
- The thermostat must not be activated or electric current must not be applied to the thermostat since this can cause irreparable damage to the thermoelectric couple.
- Filling with a watering can only does not always guarantee a complete fill (trapped air - overheating).
- Clamps on cooling system components should be examined carefully following refilling (check the coolant level while cold and top up several times as required).
- Clamps on cooling system components must also be vacuum-filled if significant amounts of coolant are drained. Drain at least two litres of coolant for vacuum-filling because otherwise the correct vacuum cannot be built up.
1. Open the bonnet.
2. Remove engine underbody panelling. -> 519219 Removing and installing cover for front underbody 519219 Removing and installing Cover For Front Underbody
3. Remove left plenum panel cover. -> 852219 Removing and installing plenum panel cover 852219 Removing and installing plenum panel cover
Tools and materials
Filling device - overview and setup
Information
- Note special features in the corresponding information for vehicles with auxiliary heater.
Vacuum-filling device components Filling device 9696
Illustration of vacuum-filling device setup
Draining coolant
WARNING
Hot fluid
- Danger of scalding
-> Avoid contact with hot fluid.
-> Wear personal protective gear.
1. If you have not already done so, carefully open the cap on the coolant reservoir using gloves or a cloth. => Cap on coolant reservoir
2. Move service clip on bleeder valve assembly to service position => Service position of bleeder valve assembly. The bleeder valve assembly -2- is located next to the filler neck for the coolant reservoir -1-.
3. Place drip pan under the radiator and open the drain plug. => Radiator drain plug
4. Proceed as follows if the cooling system needs to be bled again (in order to clean the cooling system for example):
4.1. Disconnect coolant hoses from the oil/water heat exchanger and collect emerging coolant.
4.2. Disconnect the small hose beside the generator and collect emerging coolant. A fastening screw for the generator is hidden behind the hose.
4.3. Disconnect hose for the coolant reservoir in the left wheel housing and collect emerging coolant.
4.4. Disconnect hose for the run-on pump in the left wheel housing and collect emerging coolant.
5. Fit hoses. Fit radiator drain plug.
Information
1. If you have not already done so, screw cap adapter K65 for coolant reservoir onto the reservoir.
2. Connect the flexible extension (FZ 100) to the cap.
3. Connect the vacuum pressure gauge of the bleeder tool to the flexible extension. When doing so, ensure that both shutoff valves are closed (positioned at 90° with respect to flow direction).
4. Connect the Venturi nozzle to the vacuum pressure gauge. => Connecting Venturi nozzle to vacuum pressure gauge
5. Place a canister with a sufficient amount of coolant and with an antifreeze content of -35 °C beside the vehicle close to the reservoir.
6. Push the filler hose -5- of the vacuum pressure gauge onto the canister connection. Route the return line -6- from the Venturi nozzle to a second container (bucket).
7. Connect the compressed air supply.
8. Open both shut-off valves on the vacuum pressure gauge => Shutoff valves on vacuum pressure gauge until the transparent filler hose has completely filled with coolant.
9. Close the left shutoff valve (V1) -arrow- on the vacuum pressure gauge and allow a vacuum to build up in the coolant circuit.
10. When there is a sufficient vacuum in the cooling system (indicator is in the green area), close the right shutoff valve (V2) and then disconnect the compressed air supply.
11. Re-open the left shut-off valve (V1) on the vacuum pressure gauge. The cooling system is then filled.
12. When there is no trace of vacuum present or the coolant is no longer drawn from the canister, open the right shutoff valve (V2). => Opening right shutoff valve
13. Then remove the complete filling tool (including the adapter K65).
14. If necessary, fill the coolant reservoir with coolant to the maximum marking.
15. Start the engine and leave it running at idle speed. Move the selector lever to position "P" and allow the engine to warm up.
16. Switch on passenger compartment heating. Blower setting: one bar.
17. Press the "Sport button". Activate "Sport" mode during ventilation.
18. Check the following while the vehicle is warming up.
18.1. Coolant temperature -2- and engine oil temperature -1- in the instrument cluster. Figure shows normal, acceptable values.
18.2. Feel the following coolant hoses to check that they are heating up uniformly. => Supply and return hose for radiator => Peripheral engine cooling hoses
18.3. It should be possible to force any suspected air bubbles through the cooling system by pressing the accelerator pedal from idle speed to approx. 3500 rpm -3- during the warm-up phase. Never supply power to the map-controlled thermostat using the workshop tester.
18.4. The cooling system has been filled and bled correctly if =>
- All coolant hoses are uniformly warm.
- The temperature display in the instrument cluster is in the normal range.
- The passenger compartment heater is warm.
- The electric fan for engine cooling comes on.
Subsequent work
1. Install engine underbody panelling. -> 519219 Removing and installing cover for front underbody 519219 Removing and installing Cover For Front Underbody
2. Close the clip on the bleeder valve.
3. Fit left plenum panel cover. -> 852219 Removing and installing plenum panel cover 852219 Removing and installing plenum panel cover
4. Fit lid on the coolant reservoir.
5. Conduct a test drive with the vehicle, check the fluid level in the reservoir after the cooling system has cooled again and, if necessary, fill up to the MAX marking with coolant.
6. Check the cooling system if necessary.