Just refill the cooling water yourself?

In older vehicles in particular, leaks in hoses or a leaky radiator grille cause the loss of cooling water. You can tell by the fact that either a small puddle of water forms under the car or the engine temperature display frequently beyond the “normal” 90 degrees located. Losing cooling water is no joke: If the engine is not sufficiently cooled, it can quickly lead to major engine damage.

Can I just top up the cooling water myself?

Yes, that is possible! But: Basically only temporarily! Only temporarily because the cooling water circuit must contain a special radiator antifreeze, Glysantin (Amazon Link), which prevents the cooling water circuit from freezing in winter. In summer, or when no frost is in sight, you can simply top up with tap water. The round pressure tank should be about half full (ring in the middle!). danger: If the engine was previously running, unscrew the pressure tank very carefully and with a cloth, hot steam may escape. The more frequently cooling water has to be refilled, the faster the car has to go to the workshop, of course.