What causes the coolant to overflow my overflow reservoir after idling for an extended period and after a drive? My 560SL always has a coolant puddle under the area where the overflow tube releases coolant.

When the car is cool, the coolant level is at the midway point in the reservoir. When the level is less than that the coolant light comes on when the car corners.

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1991 560SEL (254K miles)
1980 Lincoln Mark VI - Givenchy
1979 Lincoln Mark V Collector's Series
1979 Lincoln Town Car Collector's Series
1979 Ford "Effie" Pickup (in gradual transformation to a show/street truck)
1969 Lincoln Mark III (waiting for "Overhaulin" to call)
1989 Lincoln Towncar
2001 Lexus GS300 (spousal unit's daily driver)