Mitsubishi Repair: 1999 Galant Coolant Leak, coolant leak, check drain

Question
I have a 1999 Galant that has caused me more headaches than I can count. I have had problems with the cooling system since I first bought it.  I've had many "leak plugs" replaced. I've had the radiatior and water pump replaced. However there is another leak. The coolant lasts for a bout a week before needing to be replaced. (I live in the city and don;t drive far.)  

Any ideas?

Answer
Daniel: These are only ideas on my part, so from cars I have worked on with some of the same problems. Have you had all your hoses replaced, put on new connection with all the new hoses? Something like the pressurized filler cap is bad, could have a very small hole in your coolant reservoir, as the engine heats up it let's the water fill that reservoir and then as the engine cools down it pulls it back. But it could be leaking. Check drain plug in the bottom of radiator might not be working right. Check air bleeder plugs. Your thermostat might not be working right and therefore forcing the water out of the system. The car I worked on had a very and I mean a very small hole in one of the hoses, but also the coolant reservoir jug had a small leak in it too. The water has to be going someplace. You could have your radiator cap pressure tested by your dealer. Most will not charge for this and it could be something as easy as that. Hope this helps and good luck!