The 2000 4Runner is built on Toyota's bulletproof reputation, but the 3.4L V6 models suffer from a catastrophic lower ball joint failure issue and the infamous head gasket leak. These are otherwise durable trucks that rust out before they mechanically fail in most cases.
Lower Ball Joint Failure (3.4L V6 IFS models)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Clunking over bumps, Wandering steering, Uneven tire wear, Complete wheel separation in extreme cases
Fix: Replace both lower ball joints preventively. Non-greaseable design wears internally with no warning. 2-3 hours labor per side. Many techs replace entire lower control arms for easier installation.
Estimated cost: $600-1,200
3.4L V6 Head Gasket Leak (External)
Common · medium severityTypical onset: 150,000-200,000 mi
Symptoms: Coolant seepage at head/block interface, Slow coolant loss, White crusty buildup on block, Rarely causes overheating or mixing
Fix: External weep between head and block, usually rear driver side. Requires pulling heads, resurfacing, new gaskets, timing belt while in there. 12-16 hours labor. Not the catastrophic internal failure—more of a nuisance leak.
Estimated cost: $2,500-3,800
Frame Rust Perforation (all regions, worse in salt belt)
Common · high severitySymptoms: Visible surface rust on frame, Scaling and flaking near rear leaf spring mounts, Perforation near spare tire carrier, Frame cracking in severe cases
Fix: Toyota issued a frame inspection campaign but no recall for this year. Severe cases are unrepairable. Surface rust can be treated with wire brushing, converter, and POR-15/fluid film. Structural rust = scrap the truck. Inspection takes 1 hour.
Estimated cost: $0 (DIY prevention) to unfixable
Timing Belt and Water Pump Service
Common · high severityTypical onset: 90,000 mi intervals
Symptoms: None until failure, Interference engine will bend valves if belt snaps
Fix: 3.4L V6 is interference—belt failure destroys engine. Replace belt, water pump, tensioner, and idler pulleys as a package every 90k. 4-6 hours labor. Non-negotiable maintenance.
Estimated cost: $800-1,200
Transmission Oil Cooler Line Corrosion
Occasional · medium severityTypical onset: 120,000-180,000 mi
Symptoms: ATF leak at radiator connections, Pink fluid under truck, Low transmission fluid level, Harsh shifts if fluid gets too low
Fix: Steel lines rust at threaded fittings where they enter radiator. Replace lines, not just the O-rings. 2-3 hours labor, flush and refill ATF.
Estimated cost: $400-700
Rear Differential Pinion Seal Leak
Occasional · low severityTypical onset: 100,000-150,000 mi
Symptoms: Gear oil dripping from front of rear diff, Oil on inside of rear driveshaft
Fix: Pinion seal fails from age and mileage. Drop driveshaft, replace seal, reset pinion preload. 2 hours labor. Check and refill diff fluid.
Estimated cost: $250-450
Starter Motor Failure
Occasional · medium severityTypical onset: 150,000-200,000 mi
Symptoms: Click but no crank, Intermittent no-start, Works after cooling down
Fix: Denso starters are reliable but eventually fail. Located under intake manifold on 3.4L V6—major pain. 3-4 hours labor due to access. Replace, don't rebuild.
Estimated cost: $500-800
EVAP System Charcoal Canister Failure
Occasional · low severityTypical onset: 120,000+ mi
Symptoms: P0446 or P0441 codes, Fuel smell, Difficulty filling gas tank (nozzle clicks off repeatedly)
Fix: Charcoal canister saturates or purge valve sticks. Located under truck near spare tire. 1-2 hours labor to replace canister and check valves.
Estimated cost: $300-600
Buy one if the frame is solid and ball joints are fresh—these trucks run forever if rust and deferred maintenance don't kill them first. Avoid if frame shows perforation or unknown timing belt history.
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.