This could potentially be a leaking head gasket. It is generally a $25-45 test at any mechanic shop to find out for sure.
clutch fluid. Small reservoir looking like the brake overflow reservoir only about 1/3 the size.
because the entire point of the overflow resovoir is to overflow, and release uneeded water
The radiator cap could be the cause of coolant reservoir overflow or backup. Have the cap checked to see if it is bad.
Low oil causing the coolant to heat up to the point in which it's doing more harm than good so it's pushed into the overflow
A channel for an overflow of water, as from a reservoir
That's usually a good place for it, as well as the overflow reservoir. It wouldn't do you much good to put it in the windshield washer reservoir, the oil pan, or the fuel tank, after all.
Both. The reservoir is the overflow. But in the event your radiator is low, your reservoir will back it up.
If the brake fluid reservoir is overfilled, the excess fluid runs through the overflow instead of over the bodywork, which would cause damage to the paint work.
If you mean coolant in the engine oil reservoir, then yes, it is slightly possible, but very unlikely, that the engine block water jacket has developed a hole between the water and oil pathways. Other than that, the head gasket is the only place where oil and water can come in contact with each other unless your car is equipped with an engine oil cooler which is internal to the radiator (very unlikely). If you are referring to coolant being in the radiator overflow reservoir, it is supposed to have coolant in it. When the engine is cool, the overflow reservoir should be around half full.
The engine coolant reservoir or the overflow bottle.
coolant overflow/reservoir tank
the overflow res. cap is the radiator cap on the 97 cavalier