Cleaning the Cooling System

a = Locating groove

Self-made tool
Coupling (1), part No.002 545 49 28
approx. 1 m cable 1.5 sq.mm black (b) +
approx. 1 m cable 1.5 sq.mm brown (c) -
1 cable terminal +
1 cable terminal -



A. De-oiling
1 Completely drain coolant. Cooling System Drain and Refill
2 Remove coolant thermostat. Service and Repair






3 On model 116 pull plug of heating water pump (arrow) from supply line. Connect heating water pump to battery by means of self-made tool. Push "DEF" button.






On model 123 with automatic climate control and on model 126, push "DEF" button (arrow).

On model 123 with and without air conditioning, set heater lever to max. heating capacity.

4 Fill cooling system with a 5 % solution of water and a neutral cleaner, or with a mildly alkaline cleaner such as P 3-Croni (supplier: Henkel) or Grisiron 7220 (supplier: Farbwerke Hoechst).

Attention! On model 116 with heavy metal radiator, a strongly alkaline cleaner, e.g. P 3-Standard (supplier: Henkel) may be used instead of a mildly alkaline cleaner. Strongly alkaline cleaners may not be used on models 123 and 126 with light alloy radiator.

5 Run engine warm at medium speed up to approx. 80 °C (176 °F) and hold at this temperature for approx. 5 minutes.
6 Stop engine and permit cooling system to cool down to approx. 50 °C (122 °F).
7 Completely drain solution.
8 Immediately thereafter, fill cooling system twice with fresh water, run warm (approx. 5 minutes) and drain.


B. Decalcification, derusting

Attention! Prior to decalcification, be sure to de-oil cooling system, even if there is no visible oiling up.

1 After second flushing job during deoiling, fill cooling system with a 10 % (100 g/l) solution of water and citric acid, tartaric acid or oxalic acid (sold by the chemical trade) while giving preference to citric acid.
2 Run engine warm at medium speed up to approx. 80 °C (176 °F) and hold for approx. 10 minutes at this temperature. Proceed according to step 3 section A "De-oiling".
3 Stop engine and permit to cool down to approx. 50 °C (122 °F).
4 Completely drain decalcification solution.
5 Flush cooling system at least three times with fresh water while running engine for at least 5 minutes with each flushing charge.

Badly calcified cooling systems may require a repetition of the treatment. Always prepare a fresh decalcification solution and repeat flushing steps.

6 Install coolant thermostat with new sealing ring.
7 On model 116, connect heating water pump again to electric supply line.
8 Fill cooling system with specified coolant. Specifications

NOTE: For decalcification and derusting, commercial products made with the acids named above may also be used.

Chromic acid or products containing chromates are prohibited by sewage regulations.