Q: my car leaks coolant but is fine with water. it also recently had a new water pump and thermostat put in why would this happen?

You are probably just seeing "randomness" in the leak rate when you add water versus coolant; both will leak at the same rate. What you want to do, of course, is just simply get the leak pinpointed and repaired. If the cooling system leaks, it obviously will not hold maximum pressure either and the coolant will then potentially boil over and that itself creates overheating (pressure in the sealed cooling system RAISES the boiling point of the coolant). Engine coolant can leak externally through a hose, radiator, water pump, etc. or internally due to a leaking head gasket and sometimes a leaking intake manifold gasket depending on the engine design. External leaks are typically found by simple pressure testing of the cooling system. To find the leak that exists in your case, and get the required repair estimated, please request an engine cooling system leak 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.