Filling the cooling system (BMW 5 Series E12)

For models "518", "520", on which the engine cooling system does not have an expansion tank, no special precautions are required when filling the system. In this case, it is necessary to fully open the cabin heater valve.

Check the fluid level and add fluid if necessary after the thermostat opens.

For models "525", "528", the cooling system of which includes an expansion tank, the system is filled through the radiator filler neck.

Open the cabin heater tap and start the engine. After the engine has warmed up, remove air from the system by unscrewing the purge screw. Add fluid to the expansion tank until it flows out without bubbles, then tighten the purge screw.

Stop the engine, relieve the pressure in the cooling system by unscrewing the radiator cap to the first fixed position, and add fluid to the normal level.

Checking the tightness of the cooling system

Remove the radiator cap and install a hand pump with a pressure gauge in its place. Use the pump to create pressure up to 1 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.

Thermostat

Check the temperature of the main thermostat valve opening start, which should be 80±1.5°C for models "518", "520" or 84°C for models "525", "528".