An engine that is too clean and freshly cleaned should make you wonder. With an engine wash, the seller could have removed traces and concealed leaks. Hoses and seals should be dry and not brittle. Are there traces of leaked liquids? If the coolant in the expansion tank is cloudy, this can indicate a defective cylinder head gasket. When you opt for one of the used cars for sale online for yourself, look for stickers or tags with the mileage and date of fluid changes and compare the information with the odometer reading. Did you ever buy online car?