water level dropping
Saw a lot of them on C and GLK-class cars fail pressure tests that have been in multiple times for mysterious coolant leaks.
When the system won't hold pressure the coolant boils off.
Cheap and potential solution to try! Good luck!
Hopefully it's not the oil cooler, which uses coolant circulating through it to cool the oil. Gaskets can leak and the oil mixes with coolant.









