One problem related to tire valve has been reported for the 1999 Ford Expedition. The most recently reported issues are listed below.
While driving, rear driver side tire blewout, the consumer also had problems keeping air in tires, the dealer replaced the valve stems but that hasn't solved the problem, the vehicle does not ride well with the tires and vehicle has had a front wheel alignment already (firestone wilderness atx p255/70r16). Nlm.