Coolant is leaking into the engine because no coolant is found outside the engine but coolant needs to be added. What is the problem and how can it be repaired?
Coolant leak into the engine on 1992 Mercury Sable
If you look under pattern failures for this vehicle you will find that this motor blows head gaskets. This is most likely to be your problem. If your cooling system has lots of rust or electrolysis, you could also have an eroded intake manifold, that can cause coolant to leak from the water jacket to the intake manifold runner closest to it. The vacuum in the intake manifold sucks coolant into the cylinder where it causes a misfire and the loss of coolant. It is best to have this properly diagnosed before you try to fix anything. Good luck.