2006 Toyota 4RUNNER Problems

What owners report

Owners of the 2006 4Runner report one dominant concern: severe rust on the underbody frame, often found during inspections, brake work or when a suspension mount lets go. Complaint mileage for this problem spans a wide range, from roughly 76,000 up past 200,000 miles, and many describe it building invisibly behind body panels that still look clean. A separate, smaller cluster of complaints describes the rear window shattering, typically right after the rear defroster was switched on.

1. 1
   Body and structure

   Frame and underbody rust

   • 194 complaints (51%)
   • median 130,500 mi at 13.0 yrs old (126 state mileage)
   • 5 mention a crash, fire or injury
   • owner-quoted repair $6,500 (median of 8 quotes)
   • filed 2009–2026

   Complaints describe heavy corrosion of the ladder frame, with holes rusted through the frame rails, thin flaking metal, and rusted sway bar, control arm and body mounts. In several cases the rust was discovered only when a shop did unrelated work, or when an annual safety inspection failed the vehicle. Owners report that dealers ranged from offering no assistance to advising the vehicle should not stay on the road, and some say the frame was declared beyond economical repair. Reported across a wide mileage range, from roughly 76,000 to over 220,000 miles, with many clustered around 100,000 to 160,000 miles and often in states that use road salt.

   What to check: Get the truck on a lift and inspect the frame rails, mount brackets and rear control arm mounts with a pick or small hammer, especially on vehicles from salt-belt states. Ask for any inspection records showing frame condition, and be wary of fresh undercoating over rough or flaking metal.

   2 excerpts from owner complaints in NHTSA records

   “Vehicle's skid plate rusted completely off. Original owners, all family members, have kept the vehicle cleaned well underneath since first day of ownership. When we lifted the 4RUNNER up on a lift, we saw multiple rust holes in the frame as well as extreme oxidation in the center at certain places. I need to have lots of frame repair done to feel safe driving it.”

   NHTSA complaint #11402526, filed 2021-03, 223,000 miles

   “The frame, heat shields, skid plate and rear axel are severely rusted. We've owned the vehicle since 2008 and it has been garaged and kept clean. The rust is reaching a point where we're concerned about the safety of the vehicle. We've noticed it coming on for about a year - now it's growing exponentially. Apparently the Toyota tacomas have been recalled, but not the 4runners. Why!?”

   NHTSA complaint #10971429, filed 2017-04, 126,000 miles
2. 2
   Visibility (wipers, defrost, mirrors)

   Rear window shatters after defroster use

   • 30 complaints (8%)
   • median 138,000 mi at 13.2 yrs old (20 state mileage)
   • 1 mention a crash, fire or injury
   • filed 2010–2025

   Owners describe the rear glass breaking with a loud pop, sometimes while driving at low speed, shortly after the rear defroster was turned on. Several mention a burning smell beforehand and say a glass technician found the defroster connectors burnt or damaged. Complaints also describe requests for help being turned down, with some owners noting an extended warranty period that had already expired. Mostly reported between roughly 66,000 and 225,000 miles, typically in cool or damp conditions and shortly after switching on the rear defrost.

   What to check: Look at the rear defroster grid and connector tabs for dark or melted spots, and test the defroster briefly while watching the glass. Ask whether the rear glass or defroster connector has ever been replaced.

   2 excerpts from owner complaints in NHTSA records

   “On my way to the grocery store, my back window blew out while driving. It was a very loud pop! Which scared the daylights out of me! I looked in the review-mirror and the back window completely shattered. There was nobody around and I was driving too slow for it to have been a rock or debris. I was driving in san antonio texas near utsa blvd. In the turning lane, was in motion at a slow speed as I was pulling up to a red light. …”

   NHTSA complaint #11386049, filed 2021-01, 183,000 miles

   “I turned on the rear defrost in my driveway. After about 1 minute, I started to smell a slight burning smell. As soon as I smelled it, the rear glass shattered while the vehicle was in motion. I was turning onto highway 70 from bridgeway drive in cookeville, tn. The window shattered completely on highway 70 in front of mike's market at about 7:20 am on my way to work. Toyota provided extended warranty coverage for this exact issue but only through april 2018. …”

   NHTSA complaint #11144537, filed 2018-10, 196,000 miles
3. 3
   Other or unknown

   Unexpected acceleration and cruise control behavior

   • 39 complaints (10%)
   • median 41,250 mi at 4.5 yrs old (35 state mileage)
   • 9 mention a crash, fire or injury
   • filed 2006–2020

   A few complaints describe the engine speed rising on its own, either right after starting or while pulling into a parking space, with braking needed to stop the vehicle. One owner describes the vehicle surging forward while trying to stop with cruise control recently disengaged. In these accounts the cause was not identified in the complaint text. Reported at widely varying mileage, from about 41,000 to around 168,000 miles, in everyday low-speed driving situations.

   Recall 11V113000

   What to check: Confirm the floor mat is the correct one for the vehicle and properly clipped down, since an unsecured mat is the subject of a related recall. Ask whether the pedal and mat clip recall work was completed, and note any surging during a test drive.

   2 excerpts from owner complaints in NHTSA records

   “I experienced unexpected acceleration twice. Once was a month ago after starting the 4 runner in the garage. The rpms increased and as I put it in reverse the car accelerated stopping only as a pushed hard on the brakes. Today, 12-6-20, while the car was in motion and as I pulled into a parking spot, the vehicle again accelerated stopping only when I forcefully applied the brakes.”

   NHTSA complaint #11378137, filed 2020-12, 167,700 miles

   “I was coming into dewitt arkansas on highway165 on 12/13/09 at about 12:30pm with my cruise control on at about 60 MPH. I tapped the brake to disengage the cruise control and slowed down to make a right hand turn into an exxon mini mart. My 2006 Toyota 4RUNNER suddenly accelerated as I attempted to stop near the front door. As I applied pressure to the brakes I heard the anti lock brakes clicking and suddenly the 4RUNNER lunged forward striking a large pole that was in front of me. …”

   NHTSA complaint #10299572, filed 2010-01, 41,250 miles
4. 4
   Brakes

   Brake line and brake component corrosion

   • 43 complaints (11%)
   • median 88,000 mi at 7.5 yrs old (39 state mileage)
   • 9 mention a crash, fire or injury
   • filed 2006–2023

   Owners report brake lines rusted through, in some cases losing brake fluid entirely while the vehicle sat parked. Others describe a seized front caliper, a brake pedal that went to the floor on an uneven surface, and heavy brake dust on one wheel. Complaints tie much of this to the same underbody corrosion affecting the frame. Reported from roughly 35,000 to over 200,000 miles, with most accounts in the 80,000 to 210,000 mile range.

   What to check: Have the steel brake lines along the frame inspected for pitting and wet spots, and check brake fluid level and pedal feel. Ask whether lines or calipers have been replaced.

   2 excerpts from owner complaints in NHTSA records

   “4RUNNER has been garage kept, and the exterior looks perfect, lost all brake fluid, mechanic put on lift and found left rear brake line rusted through and then pointed out that the frame is severly rusted and would not pass inspection. Trailer hitch, will fall off if I try and use it. Box frame is rusted out on the bottom from front of vehicle to the very back. My wifes 2000 lexus SUV has no rust on frame and drives the same commute each day as me.”

   NHTSA complaint #10960352, filed 2017-03, 190,000 miles

   “My 2006 Toyota 4RUNNER brakes have failed when hitting an uneven surface- ie- pole. When the brake pedal was depressed, the pedal went all the way to the floor and released. The wheel spun freely without control. The brake did not activate.”

   NHTSA complaint #10306188, filed 2010-02, 35,000 miles
5. 5
   Transmission and drivetrain

   Driveline clunk and lurch when stopping

   • 52 complaints (14%)
   • median 43,500 mi at 4.5 yrs old (44 state mileage)
   • 10 mention a crash, fire or injury
   • filed 2006–2026

   Owners describe a clunking noise and a forward lurch when releasing the brake at a complete stop, starting around 40,000 miles. One complaint says the dealer initially could not identify the cause and that another vehicle with the same symptom was repaired with a new driveline. Reported from roughly 40,000 miles upward, in stop-and-go driving.

   What to check: During a test drive, stop fully, release the brake slowly and listen for a clunk or forward jerk. Ask whether the driveline or driveshaft has been serviced or replaced.

   2 excerpts from owner complaints in NHTSA records

   “I own a 2006 Toyota 4-runner after about 40,000 miles we started experiencing a clunking sound and the vehicle would lurch forward while taking your foot off the brake while at a complete stop. I addressed this with my local Toyota dealer and at the time they didn?t know what it was. This problem persisted from a once and awhile issue to doing it every time. I spoke with another person who had a v8 and the same problem, Toyota fixed his vehicle by installing a new lexus driveline. …”

   NHTSA complaint #10280458, filed 2009-08, 40,000 miles

   “Extreme wheel shimmy at highway speeds. 3 dealerships can't find a problem thought they all feel the vibration and shake. Tires are wearing prematurely. Front end components are wearing prematurely.”

   NHTSA complaint #10471916, filed 2012-08, 20,000 miles

Buying note. Frame condition is the deciding factor on this model year: inspect the underbody carefully or have a shop do it before purchase, and treat heavy rust as a repair cost rather than cosmetic wear. Beyond that, check the rear defroster and brake lines for corrosion and confirm any open recall work was completed.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.