Need advise, engine overheated driving to work. Let sit all day and engine starts and runs fine, Had truck towed home and found about 1 gallon of Evans coolant left in radiator. This am drained coolant and added distilled water to find leak. No leak found , engine runs fine, but coolant overflow bottle looks like milk, i drained a little water from radiator petcock and no milk. Engine oil and trans oil looks ok. Not sure where coolant went. Any ideas? Thanks for any help.