Ford Taurus: losing coolant, no visible leak?

I have a 2004 Taurus. My coolant level is low in the reservoir, I keep having to top it off. Car not overheating, running fine. No visible leaks on floor. No white smoke coming out of pipe on start up. Suggestions?

Check the oil and transmission fluid. If its mixing with either one you have problems

Hi so as the radiator cap has lost it's tension in the spring in the cap it is leaking it away.So a new radiator cap is needed.

If you have the 3.8 liter six cylinder engine then they were notorious for blowing head gaskets. You would lose water into the cylinder. You might notice you have a lot of exhaust coming out the tail pipe and if you run the car, then stop then try to run it again in ten minutes or so it turns over poorly. That is due to steam lock in the cylinder next to the leak. If that is the issue, it might still be covered under a secret warranty. Ask about it.