Losing coolant?

[kjp-e430]

My 2001 E430 has about 27,000 miles. On a recent road trip (with an elevation change of 5,000 feet), the "low coolant" light came on. Turns out, when I got back, I found I was about 1/2 gallon low on coolant mix. I filled it "to the black plastic" section of the reservoir, as described in the service manual. It seems like the level is lower than where I filled it up to a couple of days ago. Questions: 1. What is the normal "fill level" in this car? If I look from the side of the reservoir, I should fill to the top of the clear plastic section of the back of the reservior, where it meets the black plastic top section, right? 2. If I added too much coolant, there is an overflow path for it to escape, right? 3. I don't see any white smoke in the exhaust. Other than a hose/radiator leak, is there anything else I should be watching for? (Crossing fingers here.) Thanks!

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[sosh]

You have the normal fill level correct, and there is I believe an overflow hose. Most likely you have a hose clamp that has loosened or a bad hose. Try snugging up a bit on all the hose clamps and if that does not correct it go to the dealer and have the system pressure tested to find the leak. Its likely that its only leaking while under pressure and not sitting static with a cold engine

[redcoupe]

Also the caps go bad and they don't hold any pressrue.
If you look at the engine, look down at the lower left hand side of the radiator, most times if its a clamp its that one.
But most time its the cap.

Brian