1991 JEEP CHEROKEE

4.0L I6AWDAUTOMATICgas
5-Year Cost of Ownership
$36,414 maintenance + known platform issues
~$7,283/yr · 610¢/mile equivalent · $31,743 maintenance + $3,971 expected platform issues
Compare this engine
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2.0L Turbo I4
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2.4L I4
vs
3.2L V6
Common Problems & Known Issues

The 1991 Cherokee is a solid unibody SUV hampered by transmission cooler failures, cracked cylinder heads (especially 4.0L), and aging brake hydraulics. The 4.0L inline-six is generally bulletproof if you keep coolant clean and catch head cracks early.

Transmission Cooler Line & Radiator Failure

Common · high severity
Typical onset: 80,000-150,000 mi
Symptoms: Pink or milky fluid in transmission dipstick (coolant mixing with ATF), Transmission slipping or failure to engage after overheating, Coolant in transmission pan during service
Fix: Steel cooler lines rust through where they connect to the radiator, or internal radiator baffles fail, mixing coolant and ATF. Requires new radiator, both cooler lines, transmission fluid flush (sometimes full rebuild if contamination went unnoticed). 4-6 hours labor if caught early, 12-18 if transmission is damaged.
Estimated cost: $600-1,200 (preventive); $2,500-4,000 (with transmission damage)

0331 Cylinder Head Cracking (4.0L I6)

Common · high severity
Typical onset: 100,000-180,000 mi
Symptoms: Overheating with no obvious external leaks, White smoke from exhaust, sweet smell, Coolant disappearing into combustion chambers, Rough idle or misfire on cylinders 3 or 4
Fix: The 0331 casting (1999-2001 but swapped into earlier trucks) cracks between cylinders 3 and 4. Requires head removal, replacement with Tupy 0630 or older 7120 casting, full gasket set, machining, coolant flush. 8-10 hours labor. Many '91s have had this repair already with a bad replacement head.
Estimated cost: $1,800-2,800

Rear Main Seal & Oil Pan Gasket Leaks

Common · medium severity
Typical onset: 120,000+ mi
Symptoms: Oil dripping from bell housing area onto ground, Oil coating transmission case and crossmember, Low oil level between changes
Fix: Both 2.5L and 4.0L engines develop leaks here due to age and heat cycling. Rear main requires transmission removal (4-5 hours labor); oil pan gasket is easier but still needs crossmember dropped. Often done together. Parts are cheap, labor is not.
Estimated cost: $600-1,100

Brake Master Cylinder & Hard Line Corrosion

Common · high severity
Typical onset: any mileage (age-related)
Symptoms: Spongy brake pedal that doesn't firm up after bleeding, Pedal slowly sinking to floor under sustained pressure, Visible rust perforation on steel brake lines along frame rails, Brake fluid leaking at master cylinder or along lines
Fix: Master cylinder internal seals fail, and steel brake lines rust through, especially in salt states. Recall addressed some lines but not all. Full brake line replacement (all four corners) takes 6-8 hours. Master cylinder alone is 2 hours. Do not defer this.
Estimated cost: $400-700 (master only); $1,200-2,000 (full line replacement)

AW4 Transmission Slow Reverse Engagement (4.0L)

Occasional · medium severity
Typical onset: 150,000+ mi
Symptoms: 2-3 second delay engaging reverse when cold, Harsh or delayed 1-2 shift, No reverse at all after sitting overnight
Fix: Rear servo seals harden and leak, causing weak reverse pressure. Also check valve body and governor pressure sensor. Fluid and filter change sometimes helps temporarily. Full rebuild addresses it permanently. 8-10 hours labor for rebuild.
Estimated cost: $1,800-2,800 (rebuild)

Crankshaft Position Sensor Failure (4.0L)

Occasional · high severity
Typical onset: any mileage (heat-related)
Symptoms: No-start when hot, restarts after cooling 20-30 minutes, Intermittent stalling at idle or while driving, Check engine light with P0320 or no codes at all
Fix: Sensor mounted in bell housing fails from heat soak. Easy replacement (1 hour) but requires crawling under vehicle and working around transmission. Carry a spare if you off-road.
Estimated cost: $150-250

Vacuum Line Dry-Rot and 4WD Engagement Issues

Occasional · low severity
Typical onset: any mileage (age-related)
Symptoms: 4WD won't engage or disengages randomly, Hissing sound under hood, Rough idle or high idle fluctuation
Fix: Vacuum lines feeding the transfer case shift motor crack and leak. Also affects HVAC blend doors. Replace all vacuum lines as a set (2-3 hours). Check the axle disconnect on passenger side as well; it seizes or the fork breaks.
Estimated cost: $200-400
Owner tips
  • Replace transmission cooler lines and radiator preventively at 100k miles—cheap insurance against $3k repair
  • Flush coolant every 30k miles with distilled water mix to延 slow head cracking
  • Inspect brake lines annually if you're in the rust belt; budget for full replacement
  • The 4.0L is near-bulletproof if you stay ahead of cooling system maintenance—don't let it overheat even once
Buy the 4.0L version if the head's been replaced with a good casting and the trans cooler is recent—otherwise budget $3k-5k for deferred maintenance catching up with you.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
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