Checking the coolant level
The coolant level should be checked regularly - approximately every 4 weeks, and definitely before every long trip.
Caution: When the engine is hot, open the cap carefully.
Risk of injury! Place a cloth when opening. If possible, open the cap when the coolant temperature is below 20°C.
When opening the lid, first unscrew it a little to release the pressure. Then completely unscrew and remove the lid.
Four-cylinder engine produced before August 1988: The coolant level on a cold engine (coolant temperature approx. 20°C) must reach a maximum of 2 cm below threaded section "1".
Models 316i from September 1988 and 318i from September 1987: The coolant level on a cold engine (coolant temperature approx. 20°C) should reach or be slightly above the mark on the expansion tank (arrow).
Six-cylinder engine: the coolant level on a cold engine (coolant temperature about 20°C) should reach the "K" mark.
To avoid engine damage, add cold coolant only to a cold engine.
For topping up - even in warm weather - use only a solution of antifreeze in clean, lime-free water.
Note: On the way, especially in the warm season, it is allowed to add clean water. However, after this, adjust the concentration of the mixture as quickly as possible.
Perform an external inspection for coolant leaks if the coolant level frequently drops below the minimum mark.
(The original article is located on: BMWMAN.ru)