64 12 Venting latent heat accumulator (LWS)

Release vent plug (2) on expansion tank.

Fig 1: Releasing Vent Plug On Expansion Tank

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On vehicles with M52 engines, release additional vent plug.

Fig 2: Releasing Additional Vent Plug (On Vehicles With M52 Engines)

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During the filling procedure, do not switch on the ignition or terminal "R" because the supplementary water pump is activated and air could enter the heating circuit.

Fill expansion tank completely and wait until coolant emerges at vent point(s) without bubbles. Close vent plug(s).

Use only approved coolant, refer to 00 00... CHANGING COOLANT

Fig 3: Identifying Coolant Level

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Fit special tool 17 0 002/005 to the expansion tank and develop a pressure of approx. 1.5 bar. While doing this, check cooling system for leaks, refer to 17 00 009 CHECKING COOLING SYSTEM FOR WATER LEAKS .

Fig 4: Fitting Special Tool 17 0 002/005 To Expansion Tank

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Remove microfilter on the left side (in direction of travel), refer to 64 31 010 REPLACING MICROFILTER FOR INTERIOR VENTILATION .

Open vent plug and wait until coolant emerges without bubbles. Close vent plug again.

Fig 5: Locating Vent Plug

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Vent Heating Circuit 

Connect MoDiC or DIS.

Fig 6: Identifying MoDiC Or DIS

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Call up venting routine for latent heat accumulator in IHKA/IHKR test schedule under Service functions and start activation. The valve unit and the auxiliary water pump of the latent heat accumulator are specifically activated with this routine.

Allow valve unit to be operated for approx. 5 minutes. During this time, reopen vent plug and wait until coolant emerges without bubbles. Repeat process frequently in the course of the 5 minute flushing operation.

Fig 7: Locating Vent Plug

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Then close vent plug again.

Proceed with MoDiC or DIS. This switches off the auxiliary water pump and no coolant can emerge after the expansion tank has been opened.

Relieve pressure from cooling system. Remove special tool 17 0 002/005 from expansion tank, if necessary top up expansion tank back to top again.

The venting of the latent heat accumulator/heating circuit is thus completed.

Fig 8: Removing Special Tool 17 0 002/005 From Expansion Tank

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Vent Engine Circuit 

Allow engine to run for brief period with cooling system open and rinse the engine cooling circuit by briefly pressing accelerator pedal three to four times (up to approx. 5000 RPM).

Switch engine off again to prevent the coolant from heating up too much, which would enable it to expand.

If necessary, fill expansion tank back up to top edge and refit the screw cover.

Proceed with MoDiC or DIS. This switches on the auxiliary water pump again and the valve unit and the water valves are set in such a way that the line from the engine to the heating circuit is also vented.

Allow engine to heat up until thermostat opens. Press accelerator pedal in short bursts during warm-up phase. This completes the venting process.

Switch off engine and allow it to cool down; check coolant level and top up if necessary.

Transparent Expansion Tank: 

Fig 9: Identifying Fluid Level (Transparent Expansion Tank)

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Black Expansion Tank: 

Fig 10: Identifying Fluid Level (Black Expansion Tank)

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Venting Outside Of Workshop In Case Of Emergency Road Service: 

Add coolant, refer to 17 00 005 DRAINING OFF AND TOPPING UP COOLANT (M54) .

Fit special tool 17 0 002/005 to the expansion tank and develop a pressure of approx. 1.5 bar. While doing this, check cooling system for leaks, refer to 17 00 009 CHECKING COOLING SYSTEM FOR WATER LEAKS .

Fig 11: Fit Special Tool 17 0 002/005 To The Expansion Tank

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Remove microfilter on the left side (in direction of travel), refer to 64 31 010 REPLACING MICROFILTER FOR INTERIOR VENTILATION .

Open vent plug and wait until coolant emerges without bubbles.

Fig 12: Locating Vent Plug

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Turn on ignition and set temperature control dials to maximum heat. The heating and LWS circuit is thus flushed via the auxiliary water pump and any possible air bubbles are transported to the vent plug.

Continue flushing process for approx. 5 minutes. During this time, reopen vent plug and wait until coolant emerges without bubbles. Repeat process frequently in the course of the 5 minute flushing operation.

Fig 13: Locating Vent Plug

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Then close vent plug again.

Relieve pressure from cooling system. Remove special tool 17 0 002/005 from expansion tank, if necessary top up expansion tank back to top again.

Allow engine to run for brief period with cooling system open and rinse the engine cooling circuit by briefly pressing accelerator pedal three to four times (3000 to 3500 RPM). Switch engine off again to prevent the coolant from heating up too much, which would enable it to expand.

If necessary, fill expansion tank back up to top edge and refit the screw cover. Allow engine to heat up until thermostat opens. Press accelerator pedal in short bursts during warm-up phase. This completes the venting process.

Advise the customer to check and if necessary top up the coolant level while the engine is cold. The procedure is described in the operating instructions.

Fig 14: Removing Special Tool 17 0 002/005 From Expansion Tank

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