99 SLE makes coolant disappear!

[radomirthegreat]

The thing I think is strange about this is how the SLE has a great coolant level in the radiator and always has nice, clean oil. It doesn't burn coolant through the exhaust, and yet lately the coolant overflow tank has been totally empty. Every one and a half to two weeks, I randomly find the coolant overflow tank totally empty. It has been a week, and I saw that there's about a coin's height of coolant at the bottom of the reservoir.

What's a common place to lose coolant? I see the coolant elbow looks great, and the oil smells and feels totally fresh even after nearly 4,000 miles (synthetic). I've watched the car drive, and in no way does the exhaust smell bad at all. The spark plugs look good, and nothing smells like coolant either during driving or with the hood popped. Does this sound familiar? How else does a car lose coolant from exclusively the reservoir while consistently retaining a good coolant level in the radiator?

[LeSabre in Buffalo]

Radiator cap.

[Arriva]

Sounds like a leak or a combination of leak and a leak into the combustion chamber. A cooling system pressure test will help determine. The water pump could be leaking the coolant and may not be evident because of evaporation before it drips / puddles on the floor/ground.

[zuper8]

Sometimes I found my water pump would give a little drip or two every now and then on my SE. X2 on the radiator cap though, that ended up being the solution of a significant coolant loss problem for me.

[radomirthegreat]

I'll have a closer look at this radiator cap. It was taken off and put back on yesterday, so I'll see if that helps. Thanks for the quick responses. Is a radiator cap leak pretty hard to see judging by engine bay cleanliness?