One problem related to transmission gear slipping has been reported for the 2003 Mercury Mountaineer. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Mercury Mountaineer based on all problems reported for the 2003 Mountaineer.
Purchased the 2003 Mercury Mountaineer in 2007. We only drive the car locally for school and work and within 30 days of purchase, the car would not go into reverse. Was told the transmission was slipping and made the dealership/warranty pay for $1600 repair. Since then the check engine light comes on every 3 months. We get check fuel cap message, replaced that twice (last one from actual Ford dealership) because they told us it wasn't the original from the car. Car leaks water through the rear window/roof seal and now my light stays on when I lock the car and it tells me every time we get in the car that there is a door ajar no matter if we get out and reclose all 4 doors and back door. R&r wheel speed sensor and ball joints had to be replaced 8/29/08 for $555. Just recently had my transmission go out again (12/8/09) and had to have complete rebuild of a Mercury transmission which cost us another $4000. It still slightly vibrates going between 30 and 40 miles per hour. Also the back hatch has cracked completely down through the logo. Our Ford dealer charges $200 just to look at the vehicle!.