Filling and checking the cooling system (BMW 3 Series E21)

Filling

Open the interior heater tap and slowly pour coolant into the radiator.

Close the radiator with the plug, turning it to the second stop.

Warm up the engine.

Bleed the cooling system by turning the radiator cap to the first stop.

Remove the radiator cap and add coolant until its level is no more than 2 cm below the bottom of the cap.

Replace the radiator cap.

Checking for leaks

Remove the radiator cap and install a hand pump with a pressure gauge in its place. Use the pump to create pressure in the system up to 1.5 kg/cm², which should not decrease within 1-2 minutes.

The radiator cap has a built-in safety valve that should open when the pressure indicated on the cap is reached.

(The article text was copied from an online resource BMWman.ru)