The 1994 Mazda Navajo is a rebadged Ford Explorer, sharing the same chassis, drivetrain, and common failure points. The 4.0L OHV V6 and A4LD/4R55E automatic transmission are the weak links, with head gasket and transmission cooler failures being nearly inevitable on higher-mileage examples.
4.0L OHV V6 Head Gasket Failure
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Overheating under load, Milky oil on dipstick or oil cap, Sweet smell from exhaust
Fix: Both head gaskets typically need replacement simultaneously. Requires cylinder head removal, surface machining (often warped), new gaskets, bolts, coolant flush. Budget 12-16 labor hours. Often find cracked heads requiring replacement, which pushes this into engine rebuild territory.
Estimated cost: $1,800-3,200
Transmission Oil Cooler Failure and Cross-Contamination
Common · high severityTypical onset: 90,000-140,000 mi
Symptoms: Pink milkshake appearance in coolant reservoir, Transmission slipping or erratic shifting, Coolant in transmission fluid, Overheating transmission, Engine overheating simultaneously
Fix: Internal cooler in radiator fails, mixing coolant and ATF which destroys the transmission. Requires radiator replacement, external transmission cooler installation, complete transmission fluid system flush or full transmission rebuild if contamination has occurred. If caught early (just cooler): 4-6 hours. If transmission damaged: add 12-18 hours for rebuild.
Estimated cost: $800-1,200 (cooler only) or $2,500-4,000 (with transmission rebuild)
A4LD Automatic Transmission Failure
Common · high severityTypical onset: 100,000-160,000 mi
Symptoms: Harsh 1-2 shift or no 2nd gear, Slipping between gears under load, Delayed engagement when shifting to drive, Whining noise in gear, Loss of overdrive function
Fix: The A4LD four-speed automatic is notoriously weak, especially behind the 4.0L. Clutch packs, bands, and valve body wear out. Most need full rebuild or replacement. Budget 10-14 hours for R&R and rebuild. Many shops recommend swapping to a junkyard unit rather than rebuilding due to cost.
Estimated cost: $1,800-3,500
Front Axle Vacuum Disconnect Failure (4WD Models)
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: 4WD won't engage, Grinding noise when attempting 4WD engagement, 4WD dash light flashing or not illuminating, One front wheel spinning freely in 4WD
Fix: Vacuum-actuated front axle disconnect mechanism fails due to diaphragm rupture or vacuum line leaks. Requires replacement of axle disconnect housing or converting to manual locking hubs. Factory repair: 3-4 hours. Manual hub conversion (better long-term): 4-6 hours.
Estimated cost: $400-800
Rear Main Seal and Oil Pan Gasket Leaks
Common · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Oil dripping from bell housing area, Oil pooling under vehicle after sitting, Oil spots on driveway, Low oil level between changes, Oil-soaked starter or transmission housing
Fix: Rear main seal requires transmission removal. Oil pan gasket is easier but still labor-intensive due to crossmember interference. Often done together if transmission is already out for other work. Rear main: 6-8 hours. Oil pan: 3-4 hours.
Estimated cost: $600-1,200
Timing Chain and Guide Wear
Occasional · medium severityTypical onset: 120,000-180,000 mi
Symptoms: Rattling noise on cold start that quiets after warmup, Engine timing retarded (reduced power), Check engine light with cam/crank correlation codes, Metal shavings in oil during changes
Fix: The 4.0L OHV uses a timing chain that stretches over time, wearing guides and tensioners. Requires front cover removal, new chain, guides, tensioners, gears, and front seal. Often done during head gasket job. 8-10 hours standalone.
Estimated cost: $800-1,400
Fuel Pump Failure
Occasional · high severityTypical onset: 100,000-150,000 mi
Symptoms: No start condition with cranking, Stalling after warmup, Loss of power under acceleration, Engine sputtering at highway speed, Whining noise from fuel tank
Fix: In-tank electric fuel pump fails, often with little warning. Requires fuel tank drop and pump module replacement. 2-3 hours labor. Always replace fuel filter simultaneously (external inline type).
Estimated cost: $400-700
Only buy if under $2,000 with documented recent head gaskets and transmission work, or you're handy enough to do major repairs yourself—these are parts-bin Ford Explorers with all the same expensive failures.
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.