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full bulletin at NHTSA ↗2006 Toyota Highlander engine problems
severe 33 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
33
Recalls
0
Avg fix
$3,100
2fires
2injuries
When does it fail?
Of the 33 engine complaints filed for the 2006 Toyota Highlander, here's the actual mileage breakdown — failures cluster heaviest at 25,000-50,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Owners have filed 33 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Among the 17 model years of Toyota Highlander in our records for engine problems, this one ranks #2 by owner-complaint volume.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
TSB: OBSOLETE NOTICE August 11, 2020: This bulletin is no longer applicable and is now obsolete.
full bulletin at NHTSA ↗TSB: OBSOLETE NOTICE August 11, 2020: This bulletin is no longer applicable and is now obsolete.
full bulletin at NHTSA ↗TSB: OBSOLETE NOTICE August 11, 2020: This bulletin is no longer applicable and is now obsolete.
full bulletin at NHTSA ↗TSB: OBSOLETE NOTICE August 11, 2020: This bulletin is no longer applicable and is now obsolete.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2006 Highlander shows a pattern of engine defects that surface early in the vehicle's life. The most common failure is stripped cylinder head bolts that allow coolant to leak and the engine to overheat between 56,000 and 80,000 miles—typically just as or after the 60,000-mile warranty ends. Owners describe the bolts pulling out, the head separating from the block, and large amounts of coolant leaking onto the ground. Dealers and independent shops confirm faulty threads in the block itself. Repair costs balloon quickly: $2,300 to $2,700 for thread repair, or $5,000 to $9,000 for engine replacement or rebuild. Toyota issued a service bulletin acknowledging how to fix the problem but refuses warranty assistance for non-original owners.
Hybrid models carry a second critical defect: the power inverter fails abruptly, causing total loss of engine power, power steering, and braking at highway speeds (55–75 mph). Multiple failures have been reported on the same day at the same dealership. Owners experienced complete stalling without warning, creating dangerous situations on interstates. Toyota issued a recall for inverter replacement, but not all affected vehicles appear on the recall list.
A few owners also report water pump leaks, engine fires while parked, unintended acceleration from a standing start, and unexplained stalling, though these are less frequent. One owner reported excessive oil consumption (one quart per 500 miles) starting at 103,000 miles.
Same Toyota Highlander engine reports on nearby years: 2005 · 2008 · 2009
Failure modes owners describe
Head Gasket and Cylinder Head Bolt Failure
Engine head bolts strip or pull out, allowing coolant to leak from the head gasket area. Owners report threads in the cylinder block become faulty (some specify aluminum instead of proper metal), causing the head to separate from the block. This results in coolant loss and overheating.
When: Between 56,210 and 80,000 miles; many failures occur around or just after the 60,000-mile warranty threshold
Symptoms owners cite: Temperature gauge rises rapidly into the red zone; Coolant leaks from engine (sometimes in large amounts onto the floor); Engine overheats while driving at normal highway speeds; Check engine light illumination
Repairs/costs cited: Replacement engine costs $5,000–$9,000 installed with used engine; rebuild or thread repair $2,300–$2,700; some shops charge $600–$1,842 for diagnosis alone without reassembly
Recalls/TSBs owners mention: Toyota has issued a technical service bulletin (TSB) on how to repair the problem, yet denies warranty coverage for non-original owners and refuses to cover repairs even when failure occurs just after the 60,000-mile warranty expires
Inverter Failure (Hybrid Models)
The power inverter in 2006 Highlander Hybrid models fails without warning, causing complete loss of engine power, power steering, and power braking while driving. Multiple owners report the same problem occurring on the same day at the same dealership, suggesting a systemic defect.
When: Varies from 29,500 miles to 128,648 miles; some failures within warranty, others after
Symptoms owners cite: Complete loss of engine power while driving at speed (55–75 mph reported); Loss of power steering; Loss of power braking; Loss of accelerator response; All dashboard warning lights illuminate; Vehicle stalls without prior warning
Repairs/costs cited: Inverter replacement covered under warranty when within coverage; owners report having to pay labor costs even when part was covered; at least one owner paid $9,000 for inverter replacement when not recalled
Recalls/TSBs owners mention: Toyota issued recall for inverter replacement in some instances; Toyota stated inverter failure was a 'known problem'; some owners received recall notice after the failure occurred; however, not all 2006 Highlander Hybrid VINs appear to be on recall lists, leaving some owners without coverage
Water Pump Leakage
Water pump develops leaks allowing coolant to escape. Dealership service inspections sometimes note fluid leakage under the hood but do not alert owners to the problem or recommend repair.
When: At various mileages; one noted at time of oil change inspection
Symptoms owners cite: Fluid visible on upper part of hood; Coolant leaks from water pump area
Catalytic Converter Clogging
Catalytic converter becomes clogged, causing the vehicle to fail emissions inspection. Dealer attributes the failure to converter malfunction rather than investigating upstream causes.
When: Around 53,000 miles
Symptoms owners cite: Vehicle fails emissions inspection; Clogged catalytic converter detected during inspection
Repairs/costs cited: Catalytic converter replacement required; dealer stated repair not covered by warranty
Engine Fire (Parked Vehicle)
Engine compartment caught fire while vehicle was parked. Vehicle was routinely maintained and destroyed by fire.
When: At approximately 37,000 miles
Symptoms owners cite: Engine compartment fire while parked
Repairs/costs cited: Vehicle destroyed
Recalls/TSBs owners mention: Manufacturer was notified and complaint was filed
Unintended Acceleration from Parked Position
Vehicle rapidly accelerated forward from a parked position after engine start, without driver input. Owner could not stop the car, resulting in serious injuries and vehicle landing in a water canal.
When: No mileage reported
Symptoms owners cite: Sudden rapid acceleration from parked position; Inability to stop vehicle despite brake application; Engine rev up at high RPM
Excessive Oil Consumption
Engine consumes oil at an unusually high rate after 103,000 miles, requiring one quart every 500 miles at highway speeds.
When: At 103,000 miles
Symptoms owners cite: Excessive oil consumption (1 quart per 500 miles)
A/C Vent Odor (New Vehicle)
Bad odor emanates from the air conditioning vents when the A/C is turned off. Persisted after 1,500 miles and dealer recommended only a deodorizer application rather than addressing root cause.
When: From new (delivered with new 2006 Highlander)
Symptoms owners cite: Foul odor from air conditioning vents; Odor present when A/C is turned off
Repairs/costs cited: Dealer recommended deodorizer application
Loss of Power / Stalling (Non-Hybrid, Undiagnosed)
Vehicles lose motive power and stall while driving at various speeds. Some lose all engine power; others experience gear inoperability. Root cause not determined by dealers or independent mechanics.
When: At various mileages from 55,000 to 150,000 miles
Symptoms owners cite: Complete loss of engine power while driving; Vehicle stalls without warning; Forward gears become inoperable (reverse functional); Multiple warning lights illuminate; Vehicle can be restarted after stalling
Repairs/costs cited: No repairs completed in reported cases; one involved engine replacement several months prior
Synthesized from 33 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 3 most recent
Driving down the road at normal speed, I noticed the car overheating. This had never happened. Pulling into a 70 year old service center in cranston, rhode island, I left the car with reliable service people and they checked it out. It seems that the bolts had come loose from the engine and fluid was going into the pistons,they reported to me that the threads in the engine were faulty, I think…
Tl* the contact owns a 2006 Toyota highlander hybrid. The contact stated while driving approximately 55 MPH when the began vehicle loosing power. The hybrid warning light was illuminated and the vehicle then stalled. The vehicle was towed to the dealer where it was diagnosed as a failure in the battery cell. The dealer advised the contact that the inverter would need to be replaced. The contact…
My son was driving our 2006 Toyota highlander. He drove approx 2 miles from our house at an average speed of 35 MPH when the temperature gauge suddenly went past the red line. He drove our car approx 2 miles back to our house. We then had it towed to savannah Toyota where they checked the engine and found the head warped and the bolts stripped . I went to savannah Toyota and told them that I had…
Had engine trouble with your 2006 Toyota Highlander?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2006 Toyota Highlander?
It's a meaningful issue. 33 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $3,100.
At what mileage does the engine typically fail?
Across the 30 complaints that reported odometer mileage, most engine failures cluster between 59,871 and 104,000 miles, with the median around 75,000. A quarter of owners report trouble before 59,871; a quarter make it past 104,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2006/Toyota/Highlander.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.