Vehicle is a 2003 Neon, 2.0 liter 4 cylinder with 4 speed automatic transmission. Odometer reading is 223,800 miles. I have noticed in the last 3 days that the coolant overflow bottle is filling with coolant. Today fluid level is at the filler neck but I am NOT adding coolant. So the overflow is coming from the radiator.
Engine is not overheating as witnessed by the temperature gauge and I have not noticed in bubbling in the overflow tank. However location of the overflow bottle and opaque plastic makes viewing the coolant level and checking for bubbles difficult. I need to lower the coolant level in the bottle and then check for bubbling.
Either I have a radiator cap that has failed and is not holding pressure or this is a start of a minor head gasket leak which will progress to a major leak. I will replace the radiator cap as a cheap solution. Any other ideas as to what would cause the overflow bottle to progress to overflowing??? Would a partial collapse of the lower radiator hose cause a problem like this???