The 1998 Jeep Cherokee was available with a 6-cylinder 4.0 liter engine. As with all engines, rebuilding the 4.0 liter requires careful attention to detail. One of the most important and commonly overlooked details is the engine's torque specifications. Tightening a bolt too much can damage the component it is designed to secure, and may even break the bolt off inside of the engine block. Failure to the tighten the bolts enough can cause them to come loose and cause severe engine damage. Use a torque wrench and follow the specifications to tighten the bolts to their proper settings.
Unlike most engines, which feature an intake manifold and an exhaust manifold as separate components, the 4.0 liter engine uses a combination manifold that is removed and installed as a single component. The torque specification varies depending on the location of the manifold's bolt. Tighten the bolt at each end of the manifold to 17 ft-lb. of torque. Tighten the remaining bolts to 23 ft-lb. of torque.
The head bolts must be tightened in a particular sequence. Tighten each head bolt to 22 ft-lb. of torque, then tighten all bolts to 45 ft-lb. of torque. Tighten all of the bolts a third time to their final torque setting of 110 ft-lb.
Tighten the crankshaft's bearing caps to 80 ft-lb. of torque. Tighten the rod bearing caps to 100 in-lb. of torque.
Tighten the harmonic balancer bolt to 80 ft-lb. of torque.
Tighten the crankshaft pulley's retaining bolts to 20 ft-lb. of torque.
Tighten each of the rocker arm shaft's bolts to 19 ft-lb. of torque.
