Chances are the two conditions are completely unrelated. The coolant expansion tank is just that, it is there for expansion. It's possible that when the engine was hot the coolant expanded into the tank, when it cooled it contracted and sucked back into the radiator. If the radiator is full then just wait until you get the engine running again to check the level in the expansion tank when it is hot and add if necessary.

The electrical problem can be as simple as a poor connection at the battery. That is where I would check first, make sure the cables are tight and the contacts are clean and free of corrosion. Make sure the battery is not dead and if it is the type that has a way to check the electrolyte level that you check it. If you have no power anywhere it is probably either the battery, cables or ignition switch at fault. That is where you must start.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz