Draining the coolant
The car must be on a horizontal surface. Drain the coolant as follows:
If the engine is cold, unscrew the radiator cap and expansion tank. If the engine is hot, loosen the cap slightly, wrapping it in a rag to avoid being burned by steam, and wait until the pressure in the system drops. If you unscrew the cap quickly when the engine is very hot, the pressure drop will cause the liquid to boil. After the pressure drops, unscrew the cap.
If antifreeze is in the radiator, drain it into a clean container for reuse.
Open the interior heater tap.
Open the drain cocks at the bottom of the radiator tank and on the cylinder block (if any).
When the liquid stops flowing, clean the drain holes with a short piece of wire - they may be clogged with rust or scale particles.
Caution: If you open the drain cock only on the lower radiator hose, the fluid will not flow out of the cylinder block.
Flushing
Over time, the radiator becomes clogged with rust and scale. To flush the system, unscrew and remove the upper and lower hoses. Insert a hose into the upper neck of the radiator and flush it with water for 10-15 minutes.
If you suspect that the system is clogged, pour into it a solution of one of the special cleaning agents that are commercially available. Check that this product is compatible with aluminum cylinder heads.
Filling the system
When filling the system, use distilled water mixed with antifreeze in the required proportion. Using distilled or rainwater will significantly reduce the rate of scale formation.
The following order of filling the system is recommended:
Remove the bleed plug or disconnect the hose from the intake manifold heater unit and open the heater valve.
Pour coolant into the radiator until it begins to come out of the plug hole or the disconnected hose. Tighten the plug.
Place the hose on the block fitting and secure it with a clamp, without stopping pouring liquid into the radiator to prevent an air lock from forming.
Warm up the engine. Warming up the engine is necessary to remove air bubbles from the system. If the system is filled to the correct level at operating temperature, then topping up will be necessary when cooling down, since the volume of liquid will decrease by approximately 250 cm³ when cooling down. Check the liquid level again when the engine is hot. Add fluid to the expansion tank up to the "FULL" mark.