I've had my Sportwagen for almost 3 years and 20,000 miles. 46K on the clock. Yesterday the dash told me the coolant was low. It's down in the reservoir just enough to trigger the low coolant warning. So only a small amount is missing. Is this considered normal? None of my other vehicles do this. My thoughts are if coolant is missing there must be a leak, but I can't see one. Is there any other way coolant can go away without a leak?