Afternoon all, the coolant level light came on and after adjusting the level, i noticed it drops 1 and 1/2" every 2 days. Cant smell anything inside,no visible leaks around radiator, no white telltale in the oil(synthetic),havent checked plugs yet although car runs fine. I would have thought a leak of this magnitude would be easy to spot. Expansion cap? no water visible around cap or on the ground. The car hs done 186k. Any thoughts. Look forward to your input with thanks.