The 2008 4Runner is a solid body-on-frame SUV, but the 4.0L V6 has a well-documented secondary air injection system problem and some experienced head gasket failures. The 4.7L V8 is generally more bulletproof but less common. Transmission external cooler lines are a known weak point across both engines.
Secondary Air Injection (AIR) System Failure (4.0L V6)
Common · medium severityTypical onset: 80,000-150,000 mi
Symptoms: Check engine light with P0410, P0441, or P0446 codes, Rough cold start or extended cranking in cold weather, Failed emissions testing, Rattling noise from engine bay on cold starts
Fix: Air injection pump, control valves, or vacuum switching valve (VSV) typically fail. Most shops replace the pump assembly and associated check valves. 3-4 hours labor for pump replacement, add another 1-2 hours if lines are corroded.
Estimated cost: $800-1,500
Head Gasket Failure (4.0L V6 - 1GR-FE Engine)
Occasional · high severityTypical onset: 100,000-180,000 mi
Symptoms: White smoke from exhaust on startup, Coolant loss with no visible leaks, Overheating or fluctuating temperature gauge, Milky oil or oil in coolant reservoir, Misfires on cylinders 1, 3, or 5 (driver side bank)
Fix: This is a known weak point on early 1GR-FE engines, particularly driver-side bank. Requires cylinder head removal, machining, new gaskets, timing components, and often new head bolts. 18-24 hours labor for both banks if you're in there. Some engines have piston ring issues that show up during teardown.
Estimated cost: $3,500-5,500
Transmission External Oil Cooler Line Corrosion
Common · high severityTypical onset: 90,000-140,000 mi
Symptoms: Transmission fluid leaking near radiator or frame rails, Pink/red fluid dripping after parking, Transmission slipping or delayed engagement if fluid level drops significantly, Visible corrosion on steel cooler lines
Fix: Steel lines corrode where they run along frame, especially in salt states. Line rupture can dump all ATF quickly. Replace both feed and return lines as a set. 2-3 hours labor, more if you're also replacing the in-radiator cooler due to cross-contamination concerns.
Estimated cost: $400-900
Lower Ball Joint Wear
Common · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Clunking over bumps from front suspension, Uneven or accelerated tire wear on inside edge, Wandering or loose steering feel, Failed safety inspection due to play in ball joint
Fix: Toyota lower ball joints are pressed into the control arm; many techs replace the entire lower control arm assembly instead of pressing new joints. 2.5-3 hours per side for arm replacement, alignment required after. Do both sides if one is bad.
Estimated cost: $600-1,200
Exhaust Manifold Crack/Leak (4.0L V6)
Occasional · low severityTypical onset: 120,000-180,000 mi
Symptoms: Ticking or tapping noise from engine that increases with RPM, Exhaust smell in cabin on cold starts, Visible soot stains on manifold, P0420 catalyst efficiency code (if leak affects O2 sensor readings)
Fix: Cast manifolds crack near cylinder ports or where they mate. Driver side is more common. Manifold replacement requires significant disassembly. 6-8 hours labor for one side, sometimes you replace both while you're in there.
Estimated cost: $1,200-2,200
Front Differential Service Neglect Leading to Bearing Failure (4WD)
Occasional · medium severityTypical onset: 100,000-150,000 mi
Symptoms: Grinding or whining noise from front end that changes with speed, Vibration during acceleration in 4WD, Metal shavings in differential fluid, Increased noise when turning
Fix: Front diff service is often skipped, and the factory fill interval is vague. Bearing failure requires complete front differential rebuild or replacement. 8-10 hours labor for removal, rebuild, and reinstallation. Preventive fluid changes every 30k can avoid this.
Estimated cost: $1,800-3,000
Dashboard Cracking
Common · low severitySymptoms: Horizontal cracks across top of dashboard near windshield, Cracks starting around defroster vents, Cosmetic only, no mechanical impact
Fix: This is a widespread cosmetic issue with 2007-2009 4Runners due to substandard dash material. No mechanical fix; replacement dash or cover is the only option. Some owners filed for the class-action settlement. 4-6 hours labor for dash replacement.
Estimated cost: $1,200-2,000
The 2008 4Runner is a buy if you get a well-maintained example with service records, especially a 4.7L V8, but budget $1,500-2,000 for deferred maintenance on a typical 120k-mile V6 model.
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.