The 2018 4Runner with the 4.0L V6 (1GR-FE) is generally bulletproof, but this generation suffers from a notorious secondary air injection system failure and transmission fluid cooler leaks. The extensive engine rebuild documentation in the database is unusual and bears watching.
Secondary Air Injection Pump Failure
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Check engine light with P0410/P0418/P0419 codes, Rattling noise on cold start for 30-60 seconds, Failed emissions testing in some states
Fix: Replace air injection pump and often the one-way valves in both cylinder heads. 3-4 hours labor if just the pump, 6-8 hours if valves are also seized (common). Many techs delete the system entirely where emissions allow.
Estimated cost: $800-2,200
Transmission Oil Cooler Line Leaks
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: Pink or red fluid dripping near radiator, Transmission running hot, Low transmission fluid level, Potential for coolant contamination into transmission
Fix: Replace transmission cooler lines and often the entire cooler assembly inside the radiator. If coolant mixed with ATF, full transmission flush required. 2-3 hours for lines only, 4-5 hours if radiator replacement needed.
Estimated cost: $600-1,800
Exhaust Manifold Cracking and Leaks
Occasional · medium severityTypical onset: 90,000-150,000 mi
Symptoms: Ticking or hissing from engine bay on cold start, Exhaust smell in cabin, Failed emissions test, Visual cracks on manifold near cylinder head
Fix: Replace affected exhaust manifold(s) and all studs/gaskets. Both sides often need doing eventually. 5-7 hours per side due to tight clearances. OEM manifolds are better than aftermarket.
Estimated cost: $1,200-2,000
Front Lower Ball Joint Wear
Common · high severityTypical onset: 70,000-110,000 mi
Symptoms: Clunking over bumps, Wandering or loose steering feel, Excessive play during suspension inspection, Uneven tire wear on inside edge
Fix: Replace lower control arms (ball joints are not serviceable separately on this generation). Both sides typically done together. 3-4 hours labor, requires alignment afterward.
Estimated cost: $800-1,400
Running Board Motor and Bracket Failure
Occasional · low severitySymptoms: Running boards won't deploy or retract, Grinding noise when operating, Boards stuck in one position, Corrosion on mounting brackets in salt states
Fix: Replace motor assembly or entire running board mechanism if brackets are corroded. 2-3 hours per side. Many owners just disconnect them and leave in down position.
Estimated cost: $600-1,200
Rear Differential Pinion Seal Leak
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Gear oil dripping from center of rear diff, Low differential fluid level, Whining noise from rear end if run too low
Fix: Replace pinion seal and crush sleeve, requires diff disassembly and preload setup. 3-4 hours labor. Use OEM seal only.
Estimated cost: $500-900
Unusual Engine Rebuild Pattern (Database Anomaly)
Rare · high severityTypical onset: varies widely
Symptoms: Catastrophic engine failure, Rod knock, Severe oil consumption, Metal shavings in oil
Fix: The frequency of piston, bearing, and full engine rebuild jobs in your database is highly unusual for the 1GR-FE, which is typically a 300k+ mile engine. Suggests either severe neglect, persistent overheating, or aftermarket modifications. Full rebuild or reman engine 20-30 hours labor.
Estimated cost: $8,000-15,000
Strong buy if maintained, but verify transmission service history, check for air pump codes, and inspect ball joints carefully — the engine rebuild pattern in your data is a red flag worth investigating regionally.
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.