Cleaning the Cooling System

Service products
Anticorrosion/antifreeze agent Part No. 000 989 08 25
Citric acid powder (0.5 kg) Part No. 000 989 10 25





NOTE:
High coolant temperatures and low heating capacity may also be caused by deposits of corrosion products in the radiator or in the heat exchanger.
The deposits can be recognised from the gelatine-like mass, or if the radiator is empty and dry, from a whitish-grey layer on the radiator connection pipes. in this case, the cooling and heating system should be cleaned with a 10% citric acid solution before installing a new radiator.
The cleaning method described below is only effective if all the cooling pipes in the radiator and in the heat exchanger are still permeable. In cases of doubt, the engine should be cleaned using the short-circuit method, i.e. without heat exchanger and without radiator. If even only minor residues of corrosion products remain in the cooling and heating system after cleaning, this is likely to cause the formation of new deposits.


Scope of work





1 Flushing pipe
2 Connection Hope
3 Tap water hose

1 Drain coolant at radiator and engine (both sides).
Coolant drain plug on radiator remains open.
2 Remove thermostat and install forcibly opened thermostat 000 589 74 63 00 with seal. The short circuit passage is thus sealed off and the water flows through the radiator to the coolant pump.
3 Connect flushing pipe 117 589 00 90 00 with connection hose (2) between radiator and coolant hose.
4 Connect a tap water hose (3) to the flushing pipe (1)
5 Open expansion tank cap and pull off hose to the overflow tank.
6 Switch off circulation pump to flush the heat exchanger.
To do so, switch on ignition and:
a) On vehicles with automatic heater engage both temperature dials to position "Max".
b) On vehicles with automatic climate control, press the push-button "Defrost".
7 Open the vent valve of the supplementary heater.
8 With engine running (approx. 2500/min) flush cooling and heating system with running water for approx. 5 minutes to flush out the remaining corrosion-antifreeze protection agent.

CAUTION: During the flushing process, the cooling system must always be full. Regulate additional quantity accordingly.

9 Drain flushing water in the radiator completely and screw in drain plug.
10 In a clean vessel, prepare a solution of 1.5 kg citric acid powder (0.5 kg, part No.000 989 10 25) and approx. 5 l of water.
11 Fill the cleaning solution into the expansion tank and top up with water to the mark on the expansion tank.
12 Close the vent screw of the supplementary heater.
13 Close expansion tank cap.
14 Run engine for 15 minutes at approx. 2500/min. The solution must now flow through the heat exchanger.
15 Drain cleaning solution.

CAUTION: Dispose of the cleaning solution (citric acid mixture) in an oil and water separator as used in workshops.

16 Open vent screw of the supplementary heater.
17 Flush cooling and heating system with running engine (2500/min) for approx. 10 minutes with running water. The water must flow through the heat exchanger.
18 Remove flushing pipe connection and connect coolant hose to radiator.
19 Install normal thermostat.
20 Screw in coolant drain plug in radiator.
21 Replace overflow tank.
22 On vehicles fitted with auxiliary heater, connect plastic hose to bleeder valve and open valve.
23 Slowly pour in fresh coolant up to the mark (pay attention to anticorrosion/antifreeze agent).
a) On vehicles With automatic climate control press push-button "Defrost", With automatic heater, engage both temperature selector dials in position "Max".
b) Warm up engine while intermittently pressing the accelerator pedal. At approx. 60 °C, close the filler neck with a cap and switch supplementary heater to immediate heating.
c) Vent until the thermostat opens and the coolant runs out of the vent valve free of bubbles. Now close the vent valve.
24 Check coolant level below 90 °C and top up to specified level, if necessary.