One problem related to bumper has been reported for the 1998 Toyota 4Runner. The most recently reported issues are listed below.
Rear bumper has a design flaw causing it to accumulate dirt on inside "lip". If not cleaned out properly, which is impossible to do, rust will start to eat through the bumper from the inside out. This causes an unsafe condition because the integrity of the bumper is compromised leading to a lack of protection from the rear, not to mention one ugly sight.