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Q: Car overheating after losing green fluid from radiator.

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My car had a radiator leak, but as long as I kept adding fluid there was no problem. My daughter forgot to put the radiator cap back on after adding fluid. After driving it for a while, she noticed and put the cap back. The car overheated soon after. I checked it out and noticed green fluid on the right side of the radiator. What is going on with my radiator?

A: The green fluid on the side of the radiator...

The green fluid on the side of the radiator could just be from the cap being left off. It also could be from a leak. I believe your car overheated because while driving with the cap off of the radiator too much coolant came out. This left room for air in the cooling system which got sealed in by replacing the cap. An air pocket in your coolant system could block coolant from being able to flow through the radiator and cool your engine down. I would enlist the help of a mechanic to help find your coolant leak so you don't need to worry about the cap getting left off again.

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