I just replaced the water pump in my 2005 Ford Escape V6.
I discovered that each time I fill the coolant reservoir with coolant and drive the car, by my next stop the coolant reservoir will be completely empty. I can't see water leaking or dripping from anywhere in the car. This has happened 3 times now.
What could be the problem?
A bad radiator cap can explain this.
If the cap opens at a lower pressure than what the cooling system is rated at then coolant will be released through the overflow tube once that pressure is achieved, which it will under normal operation.
I would test/replace the radiator cap and see if that remedies the symptoms.
The first comment is that there MAY be a special fill procedure for your car. If you are not observing the fill procedure, you may not be putting enough coolant in, and OF COURSE the car will drain the tank, to fill the cooling loop, once the thermostat opens.
The second comment is that this sounds as though the car is burning coolant. Think "blown head gasket". Start by taking a look at the engine oil. Your shop may be able to tell something with an exhaust analyzer.
I had a problem with a 1990 Chevy Lumina 4-door sedan gradually draining the coolant tank. Newspapers under the car revealed a leak SOMEWHERE, but I couldn't see where. I finally got lucky, and saw a leaking gasket at the bypass union, that turned out to be a worn union. (That repair was what triggered my search for a replacement vehicle: getting a replacement part was a lot harder than it should have been.)
Of course a leak is a possibility and should be checked out as other respondents suggest. It is also possible that you did not completely fill the coolant system—for example, you may have forgotten to turn on the heat (so that coolant will go into the heater core sub-circuit). When I change coolant, i run the engine for 10-15 minutes with the radiator cap off, and periodically bounce the front end of the car up/down. i am always amazed at how much air “burps” out from the system. i may add another couple of pints of coolant during this process. It could be that you’re doing the same thing by refilling your reserve tank several times.
