Q: I put a brand new thermostat in my car and after that my heat went out and I noticed water on floorboard.. what causes this?

If you did not have an overheating problem prior to the repairs that you have listed, a likely cause of the present overheating is trapped air and/or low coolant level. Trapped air can prevent coolant circulation thus causing the no heat condition in the cabin, too. If there is water or antifreeze on the cabin floor, that would signify a coolant leak. If coolant is leaking, the source can be found with simple pressure testing. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine overheating diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.