Tire Valve problems of the 2008 Ford Mustang

1. On September 1st, my tire pressure on my car suddenly went down and I blew out the front passenger side tire. I took it in to the Ford dealer the next day and they repaired the tire valve stem free of charge because they said it was defective. Today (09/30/08) I was driving down the highway and my back passenger tire went flat. I took it in to the Ford dealer after I checked the valve stem and saw that it was cracked all around the base. I told them about the previous event and told them I was sure it was the valve stem. They called me back and said that there was no way they could know because I had run the tire while it was flat and it would not be warranted. They would not even check the valve for me. They said I would have to wait 3 days to get the tire in stock and I told them I have to commute to work and I could not drive on a doughnut for 3 days. They sent me to a tire dealer in town that would have that size (but not the same brand) tire in stock. I went there and they fixed it but it cost me $172 and they showed me my other 2 driver's side tire valve stems were cracked and the back driver's side valve stem was about to come off. Now I have to go back to the Ford dealer and hope they replace them without a fight. 2. This has occurred 2 times now with another 2 guaranteed if I do not take action now. 3. The first tire Ford replaced only the valve stem (and they put one that was way too long on my tire so now it is fixed but it sticks out which I am sure is another hazard). The second one, the valve stem could not be repaired because the tire was unsafe to drive on. I had to go to a tire dealer and have them put on a brand-new different brand of tire.