The "Low Coolant" warning light in my car came on a few weeks ago. I checked the coolant tank and noticed it was below the minimum mark. I topped up to the maximum mark and the warning light disappeared. But about a week later, it came on again. This has been going on for five weeks, but I do not see any leakage anywhere - whether in the engine compartment or on the floor where I park my car. What is the problem? Your car definitely has a leak.
The reason you cannot see the source is likely because it is a small leak, which evaporates when the fluid falls on the hot engine.
When your engine is switched off, there is no pressure in the cooling system and the coolant may not leak.
You should send your car to a workshop, which can pressure-test the cooling system.
Such a test will simulate the pressure in a running engine and uncover the source of the leak.
It is important to have this fixed quickly because the leak can only get worse. If so, it could lead to a overheating of the engine and costlier damages.