1990 JEEP CHEROKEE

Typical onset: 120,000-180,000 mi

Symptoms: Overheating, especially after coolant system neglect, White smoke from exhaust, coolant loss with no visible leaks, Milky oil on dipstick or oil cap, External coolant weeping between head and block

Fix: The 0331 casting heads crack between cylinders 3-4. Requires head removal, magnaflux inspection, often replacement with newer 'Tupy' casting. Surface block, new gaskets, timing set inspection while apart. 12-16 hours labor if no machine work needed, add 3-5 hours if head needs replacement.

Estimated cost: $1,800-3,200

Typical onset: 80,000-150,000 mi

Symptoms: 4WD won't engage or grinds when attempting engagement, Hissing sound from front axle area, Check engine light with 4WD system codes, Intermittent 4WD function, works when cold, fails when warm

Fix: The vacuum-operated axle disconnect uses rubber diaphragms and o-rings that deteriorate. Requires replacing the axle disconnect housing, shift motor, or converting to manual 'posi-lok' cable system (common aftermarket fix). Also check vacuum lines from transfer case switch. 3-5 hours labor for OEM repair, 2 hours for cable conversion.

Estimated cost: $400-800

Symptoms: Transmission fluid leaking at radiator connections, Pink or milky transmission fluid (coolant contamination), Transmission slipping or delayed engagement after radiator work, Visible rust and corrosion on steel cooler lines at frame

Fix: Steel cooler lines rust through where they run along frame rails, especially in salt states. Internal radiator cooler can fail, allowing coolant into ATF and destroying transmission. Must replace lines (upgrade to stainless or rubber), external cooler recommended. If coolant mixed with ATF, full transmission flush or rebuild required. Lines alone: 2-3 hours. If trans contaminated, add 8-12 hours for rebuild.

Estimated cost: $300-600 for lines; $1,800-2,800 if transmission damaged

Typical onset: 100,000-180,000 mi

Symptoms: Coolant smell from engine bay, visible drips below intake, Overheating or low coolant warnings, Coolant puddle on passenger side of block, Steam from under intake manifold area

Fix: Small crossover tube behind throttle body develops pinhole leaks or o-ring failures. Requires intake manifold removal for access, new tube and gaskets. Often done during head gasket job. 4-6 hours standalone, less if combined with other work.

Estimated cost: $450-750

Typical onset: 150,000+ mi

Symptoms: Oil dripping from bell housing area or rear of engine, Oil spots on driveway, low oil between changes, Visible oil coating on transmission case, Clutch contamination and slipping (manual trans)

Fix: Both 2.5L and 4.0L develop rear main seal leaks with age. Requires transmission removal. Oil pan gasket leaks common due to overtightening and cork gasket compression. Rear main: 6-8 hours (manual), 5-6 hours (auto). Oil pan: 2-3 hours with potential exhaust removal.

Estimated cost: $600-1,000 rear main; $250-450 oil pan

Symptoms: Visible rust perforation in lower rear quarters behind wheels, Bubbling paint along rocker panels below doors, Liftgate hinge mounts rusting through, liftgate sags or won't stay up, Floor pan rust-through in cargo area or under rear seat

Fix: Unibody construction means structural rust is a safety issue, not cosmetic. Rear quarters trap dirt and moisture. Liftgate hinge rust causes alignment issues and water leaks. Proper repair requires cut-and-weld panel replacement. Rockers: 8-12 hours per side. Liftgate area: 6-10 hours. Many are patched poorly.

Estimated cost: $1,500-3,500 per area for proper metalwork

Typical onset: 100,000+ mi

Symptoms: Cruise control won't set or drops out immediately, Servo makes clicking noise but doesn't hold speed, Works intermittently, fails after engine warms up

Fix: Vacuum-operated cruise servo diaphragm tears or vacuum lines crack. Check valve at intake manifold also fails. Requires servo replacement or rebuild, vacuum line inspection. Subject of recalls for sticking servos causing unintended acceleration. 1-2 hours labor.

Estimated cost: $200-400