One problem related to frame rust has been reported for the 1998 Kia Motor Sportage. The most recently reported issues are listed below.
Rear frame rust/rot is incredibly excessive. Noticed today while checking tire pressure. Entire underside of frame is completely rusted through. Rear cross member in terrible shape. Visible deterioration happened quickly. Purchasing the car in 2012 there was no sign of rot on the frame. Now I feel uncomfortable driving the car, or selling it to someone else for that matter. As a mechanical engineer, the integrity of the square tube frame is compromised to the point that safety in a rear end collision is in question, any kind of trailer load would be impossible and unsafe. Really a danger to the general public because it could fail at any time.