Inline engines are hard on exhaust manifolds. Pre-’00 Wranglers equipped with the 4.0L engine are known to develop an exhaust manifold crack, while the cracks on the redesigned manifold for the ’00-’06 are less common. The cracks are sometimes hard to see but easy to hear. There is a small contingent of Jeep owners who choose to ignore the exhaust leak and chalk it up to “a Jeep thing”—Don’t get caught up in that nonsense. If it’s cracked, fix it. It’s a labor-intensive job, but it isn’t all that difficult.