Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2006 Mercury Mountaineer owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2006 Mercury Mountaineer. The contact stated that her husband informed her that the vehicle had experienced an unknown radiator failure. The vehicle was taken to an independent mechanic, where the radiator was replaced; however, the failure reoccurred. The vehicle was repaired for a second time by an independent mechanic; however, the failure persisted. The local dealer was made aware of the failure. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 143,869.
My 2006 Mercury Mountaineer was leaking coolant due to a crack in the radiator. After searching online forums, I have learned that has been a long standing issue with many of this vehicles owners. Unfortunately for owners, Ford issued a tbs in 2009 just in time for most of the affected vehicles' warranties to expire. Some owners are on their 3rd or more radiator replacement, I am only on my first. I petition that Ford recalls this issue before myself and others have to repeatedly pay for this clear design problem with their hard owned money. This problem also poses safety risk to the passengers operating these vehicles and to any animals attracted to the sweet smell of the coolant from affected vehicles whose owners who May not yet know this issue or cannot afford to fix it.
I purchased this vehicle recently with only 40,000 miles. The car keeps stalling or dying as you May say as I drive. It will be okay for a short period of time and then just die right on the highway! Once it dies once, the car will continue to do so over and over again until the engine has cooled down. I have the engine codes of p2104, p2111 and p2135 with a refere to p2101. I have brought it to several mechanics and paid well over $1,000 to fix this problem and it just continues. I am afraid my family May all die! Were on 93 recently heading toward boston and my car died right at the intersection of 495. I had all my children in the car and it would not restart. I have fixed the fuel system (error code last time), had a complete tune up, and throttle sensor etc.
Truck cooling system died which caused the truck to catch fire while driving down the highway, smoke poring out, state troopers had to assist us. My daughter was scared to death and now refuses to get back in the truck even though we got a new engine. To make matters worse we spent 3000 on and engine...500 on cooling system and had the transmission reprogrammed. The truck is still have major problems and now for says it needs the transmission rebuilt or replaced. All of this is out of pocket. We cant even trade it in bc they will only give us 1/2 of what we paid for it 2 yrs ago. Nightmare and makes me sick that Ford doesn't care.
Tl* the contact owns a 2006 Mercury Mountaineer. The contact stated that while driving at approximately 25 MPH, an unknown warning light illuminated. The vehicle was towed to an independent mechanic where the radiator was replaced, but the failure recurred. The vehicle was then taken to an independent mechanic where it was diagnosed that the three way heater hose needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 106,000.
Tl* the contact owns a 2006 Mercury Mountaineer. While driving at approximately 55 MPH, the vehicle intermittently stalled without warning. The vehicle was taken to an independent mechanic, who diagnosed that eight spark plugs needed to be replaced. The vehicle was repaired, but the failure recurred multiple times and a coil pack was placed to prevent the spark plugs from blowing out. The manufacturer was not notified of the failure. The approximate failure mileage was 105,000.
2006 Mercury Mountaineer driving on the highway, suddenly the coolant temperature went up crazily and the engine sounded horrible and lost power. Fortunately stopped by the roadside and found the radiator was leaking and coolant is almost empty. Searched around the web and found that for 4.0 engine from Ford and Mercury, this is pretty normal problem due to a design defect. People are changing radiator every year. Never heard such ridiculous thing that nowadays the radiator last so short time. It should last life time of the car. Ford apparently knew it, however, they only announced a TSB in 2009 when most of the warranties were gonna expire. They should issue a recall. This is a design problem and it poses life threatening risks. I guess they just don't care about customers. The customers need to repair out of they own pockets, which support Ford's chain dealers service departments. …
Had to replace two radiators within 30,000 miles of replacement. Exactly how many complaints, or should I say deaths (?) are needed to trigger an investigation of a company gladly receiving assistance while outputting inferior vehicles. No vehicle manufactured in 2006 should need three new radiators within 3 year and 70K miles. Stop letting Ford off the hook and get serious about getting to the bottom of their issues. Just do a search on 2006 Mercury Mountaineer and you will clearly see there are issues with the cooling as well as the automatic transmission. In fact, our model has the same issue that others have reported with the automatic transmission and it will sometimes no moves gears, slip a gear, and tug like it is pulling out of mud at a stop light. …
Tl* the contact owns a 2006 Mercury Mountaineer. While driving approximately 40 MPH, the contact noticed the temperature gauge displayed a "high temperature" reading. The vehicle was pulled over to the side of the road and the engine was turned off. The engine overheated with excessive leakage of coolant. The contact dispensed coolant into the radiator reservoir. The vehicle was able to continue for approximately ten miles before the identical failures recurred in which the radiator required additional coolant. The failures occurred whenever the vehicle was in operation. The authorized dealer was notified of the malfunctions and they informed that there was a technical service bulletin regarding the engine and engine cooling: cooling system: radiator assembly. The bulletin number was 0638. The vehicle was not being driven at the time of the complaint due to the potential safety hazard. …
Tl contact owns a 2006 Mercury Mountaineer. The contact started the vehicle and it immediately stalled. The vehicle was towed to a local dealer and they stated that the entire computer system failed and was replaced. Two months later, the engine light illuminated. She took the vehicle to the dealer and they stated that there was emission failure. The contact also began experiencing failures with the front passenger window and the frame was replaced. The engine light still continued to illuminate and the dealer stated that it was due to the catalytic converter, in addition to the transmission. The dealer did not know how to repair the failures. The current mileage was 1,500 and failure mileage was 411.
Engine complaints in other Mountaineer years
Frequently asked questions
How common are engine problems on the 2006 Mercury Mountaineer?
NHTSA has 56 complaints about the engine & cooling of the 2006 Mercury Mountaineer, 48% of the model year's 117 complaints. The component named most often is cooling system (19 mentions).
Is there a recall for 2006 Mercury Mountaineer engine problems?
No. NHTSA lists no engine & cooling recall for the 2006 Mercury Mountaineer, though it has 1 recall for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2006 Mercury Mountaineer engine problems start?
Half of the complaints with a recorded mileage happened before about 59,000 miles, and 4% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 1 injury to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.