2001 Mitsubishi Diamante Problems
- Complaints
- 78filed with NHTSA
- Median mileage
- 59,750miles, 57 complaints with mileage
- Recalls
- 2campaigns on record
- Trend
- StableComplaints filed in the last 3 full calendar years are within 25% of the 3 years before.
- NHTSA crash rating
- —overall rating starts with 2011 models
- EPA fuel economy
- 18 mpgcombined, 3.5L 6-cyl FWD · 16 city / 23 hwy
Sources: NHTSA records for the 2001 Mitsubishi Diamante (complaints, recalls, investigations), EPA fuel economy. Report an error
What owners report
Owners of this model year most often describe a coolant smell inside the cabin, windows that fog and will not clear, and a heater core that has to be replaced — usually in the 30,000 to 80,000 mile range and worse in cold weather when the defroster is used. A smaller group of complaints covers engine cooling components and the automatic transmission, and a few describe front-end or rear-suspension looseness.
- Visibility (wipers, defrost, mirrors)
Heater core leak (coolant smell, fogged windows)
- 56 complaints (72%)
- median 58,925 mi at 4.4 yrs old (44 state mileage)
- 3 mention a crash, fire or injury
- owner-quoted repair $826 (median of 18 quotes)
- filed 2004–2011
Complaints describe a sweet, syrup-like coolant odor coming from the vents, especially with the heat or defroster on, along with windows that fog over and do not clear even at full defrost. Many owners report wet carpet on the passenger side or coolant puddling on the floor, and several say a dealer traced it to the heater core or its O-rings and quoted a replacement. A few mention coolant reaching a control module or wiring under the dash. Repair estimates in the complaints commonly run in the several-hundred to roughly one-thousand dollar range, and some owners had the core or its seals replaced more than once. Reported mainly from roughly 25,000 to 85,000 miles, frequently in winter or cold-weather use when the heater and defroster are in constant use.
What to check: Before buying, run the heater and defroster and smell for coolant, and lift the passenger-side floor mat to check for damp carpet or staining. Ask whether the heater core or its O-rings have been replaced and keep an eye on coolant level.
2 excerpts from owner complaints in NHTSA records
“This is a Mitsubishi Diamante 2001 ls. I'm experiencing pungent smell of anti-freeze inside the car as soon as I turn on heating. The dealer I got the preowned car from won't fix the problem unless I can show them the leak in heater core. Anti-freeze contains ethylene glycon and the fumes are highly toxic. Fixing the the heater core will cost $1000. …”
NHTSA complaint #10114715, filed 2005-03, 40,000 miles“Heater core, producing toxin fumes, inside the car. This is my only means of transportation, I have a two year old child who I drive around every day.this is going to cost me $400.00 dollars in labor, which I do not have, I have no idea what the heater core cost. But it must be fix before my family or I come down with some serious illness.”
NHTSA complaint #10108324, filed 2005-01, 60,000 miles - Engine cooling
Engine cooling — overheating and coolant loss
Mentioned in 8 of 60 sampled complaints
Some complaints describe the temperature gauge climbing or the car running hot alongside the coolant smell, and in some cases a dealer first replaced the thermostat or checked for external leaks before the heater core was identified. Others describe having to top up coolant repeatedly, and one report describes a serpentine belt shearing off and stalling the car. These complaints read as the same coolant-loss story seen from the cooling-system side. Mostly reported between roughly 40,000 and 110,000 miles, often noticed after repeated coolant top-ups.
What to check: Check the coolant reservoir level and look for dried coolant residue around the radiator and hoses. Ask whether the thermostat, water pump, or drive belts have been serviced.
2 excerpts from owner complaints in NHTSA records
“Dt: consumer owns a Mitsubishi 2001 vehicle with less than 26,000 miles the heater core is not working. We noticed some type of a fog in the window. We started getting smoke in the car, and the front glass fogs up and doesn't clear up. Also, it has a strong smell of antifreeze. We have to keep putting antifreeze in the car.”
NHTSA complaint #10123921, filed 2005-06, 26,000 miles“My car is making me sick. I purchased my car in aug. 2001 and began to notice a smell in the car and fume closely resembling that of radiator coolant. The car was assesed by a Mitsubishi district manager and service personnel from my dealer and deemed to be sound. In the mean time I have suffered with runny eyes and intermittent paralysis in the right side of my face dependent on the amount of time spent in the car. I have contacted Mitsubishi numerous times about this and received no assistance. …”
NHTSA complaint #10112583, filed 2005-03, 5,000 miles - Suspension
Rear knuckle bushings worn
Mentioned in 4 of 60 sampled complaints
A small group of complaints describes the rear of the car feeling loose or unstable, with one owner saying both rear knuckle bushings were worn and the body seemed to move on the frame. Others describe front-end vibration, poor alignment, and tires cupping or making noise during turns, with parts replaced but the symptoms persisting. Reported from about 60,000 to 105,000 miles, often noticed as vibration or looseness during turns.
What to check: On a test drive, listen for clunks over bumps and feel for vagueness in turns. Ask for a suspension inspection of the rear knuckle bushings and front-end alignment before purchase.
2 excerpts from owner complaints in NHTSA records
“I am feeling a constant vibration on the front end of car, and I just replaced the front tires. I checked to see if the weights are still on the rim and they are. All of a sudden I started to hear a very loud noise and when I pushed the gas pedal the vibration would get worse.”
NHTSA complaint #10197467, filed 2007-07, 101,890 miles“2001 Mitsubishi Diamante. We have had it about six months. I have had it in to a very reputable service station and have come up empty on the following problem. The car has new tires, this occurred before and after they were installed. During more aggressive turning the car gets very unstable, bad enough to lose control. The service shop checked out all the obvious front end stuff along with the three bushings on each front wheel assembly. For the most part the car tracks straight down the road and is smooth and true. …”
NHTSA complaint #10221262, filed 2008-03, 63,000 miles
Buying note. The heater core leak is the single thing to check on this model year: smell for coolant with the heat on and look for a wet passenger-side floor mat, and get a quote if it has not been replaced. Otherwise, have the cooling system, suspension bushings, and transmission checked, and confirm the two label/manual recalls were 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.
NHTSA recorded 78 consumer complaints for the 2001 Mitsubishi Diamante. 57 of the complaints include a mileage, and 37% of those were filed for vehicles with under 50,000 miles; the median is 59,750 miles. Of all complaints, 6 an injury, according to the filers. NHTSA lists 2 recall campaigns and 26 technical service bulletins for this model year.
Not compared (before 2008). Model years 2008–2023 of the same vehicle that have at least 25 complaints are compared, and a model needs at least 3 of them.
Which parts are reported most
Complaints can name more than one part, so the counts add up to more than the total. Select a part to see its complaints, recalls and bulletins.
- Engine cooling14 18%
- Brakes4 5.1%
- Suspension3 3.9%
- Tires3 3.9%
- Equipment1 1.3%
- Other or unknown1 1.3%
- Seat belts1 1.3%
- Body and structure1 1.3%
Also reported: Vehicle speed control (1), Wheels (1).
Example complaints
Visibility (wipers, defrost, mirrors): “For no particular reason my car fills up with the smell of anti-freeze coolant when I turn on the heater. I have read that this is caused by leaking 0-rings and that this will damage the computers which are underneath the leak. The car is a 2001 Mitsubishi Diamante l.s. The dealer says it is not a common issue. Google says otherwise.”
NHTSA complaint #10188952, filed 2007-04, 58,100 milesEngine cooling: “Anti freeze odor is overwhelming in the car, especially when the heater is run. I have had the car since it was new, and had the same problem after only a couple of months. The dealership fixed the issue by installing a new gasket, but the fix has lasted only a couple of years. My wife and I have been having a variety of respiratory illnesses recently, and I believe these fumes are a contributing factor.”
NHTSA complaint #10180810, filed 2007-01, 75,000 milesBrakes: “The manufacturer and the dealer state that it is normal wear and tear to have to replace and or turn rotors every 18000 to 20000 on thier cars even though the brakes have not failed.”
NHTSA complaint #756007, filed 2001-12Transmission and drivetrain: “I have a 2001 Mitsubishi Diamante, and am having problems that seem to run rampant among this model/make. My heater core went out at about 100k miles; my ABS light stays on (due to a speed sensor fail), which renders the whole anti-lock system useless; and now my antenna mast is broken. All of these problems are pricey to fix, and most Diamante users I have found experience at least a few of these conflicts. Another problem I have seen many comments about is transmission failure at 113k miles. My car has exactly that. …”
NHTSA complaint #10378164, filed 2011-01, 100,000 milesMileage when problems were reported
37% of the 57 complaints with a mileage were filed for vehicles with under 50,000 miles; the middle half falls between 45,000 and 75,000 miles.
Complaints by year filed
Trend: stable. Complaints filed in the last 3 full calendar years are within 25% of the 3 years before.
Fuel economy and running cost
EPA ratings for each 2001 Mitsubishi Diamante version. Annual fuel cost is the EPA's estimate at its current fuel prices for 15,000 miles a year (55% city driving).
| Version | Engine | Transmission | City | Hwy | Comb. | Fuel / yr |
|---|---|---|---|---|---|---|
| Diamante FWD | 3.5L 6-cyl | 4-speed automatic | 16 | 23 | 18 | $4,550 |
Source: U.S. EPA and Department of Energy, fueleconomy.gov. Ratings are for comparing vehicles; real-world mileage varies with driving and conditions.
Recalls and investigations
- 04V428000Sep 1, 2004Equipment › Other › LabelsCovers: Mitsubishi Diamante 1998–2004, Eclipse 1998–2005, Montero 1998–2004 +9 more
Certain passenger vehicles fail to conform to the requirements of federal motor vehicle safety standard no. 208, 'occupant crash protection.' the bilingual english/spanish removable air bag warning labels affixed to the dash and to the sunvisor do not meet…
- 04V067000Feb 11, 2004Equipment › Other › Owners/service/other manualCovers: Mitsubishi Diamante 2000–2003, Montero 2001, Outlander 2003
Certain sport utility and passenger vehicles fail to comply with federal motor vehicle safety standard no. 225, "child restraint anchorage systems." the owner's manual does not contain a step-by-step description for headrest adjustment when installing a…
Recall details for the 2001 Mitsubishi Diamante → · Check a VIN at nhtsa.gov/recalls
Technical service bulletins
TSBs are manufacturer notes to dealers about known repair procedures. They are not recalls and do not by themselves mean a vehicle has a fault. 26 on record; the latest 10 are shown.
- 10240443Jul 21, 2023Equipment. This is a Dealer Letter sent to dealers informing that Mitsubishi Technical Training has launched the 3rd quarterly technician quiz for 2023.
- 10235609Apr 24, 2023Body and structure. This Technical Service Bulletin provides instructions and material safety data sheets for removal of rap-film adhesive residue.
- 10235608Apr 24, 2023Equipment. This Technical Service Bulletin reviews the regulations that require a label showing the reduction in load carrying capacity be affixed to vehicles when the total net weight of accessories is more…
- 10235606Apr 21, 2023Equipment. This is a Dealer Letter sent to dealers informing that Mitsubishi Technical Training has launched the 2nd quarterly technician quiz for 2023.
- 10211530Apr 7, 2022Other or unknown, Exterior lighting. This Technical Service Bulletin was sent to dealers to explain the difference between normal dew condensation, which is a natural phenomenon, and water penetration caused by improper sealing or a…
- 10169006Nov 26, 2019Equipment. This is a service newsletter (Tech Talk) that was sent out to dealers.
- 10163703Jul 30, 2019Equipment. This is a Technical Service Bulletin sent to dealers. This bulletin supersedes TSB-18-00-003, issued April, 2018, to add updated information for Carrying Capacity Reduced Label.
- 10130468Feb 27, 2018Equipment. This is a message sent to dealers, to inform them that an update for MEDIC will be available.
- 10130469Feb 26, 2018Equipment. This is a service newsletter (Tech Talk) that was sent out to dealers.
- 10170074Aug 28, 2015Visibility (wipers, defrost, mirrors), Engine cooling…. This is a service newsletter (Tech Talk) that was sent out to dealers.
Other model years of the Mitsubishi Diamante
| Year | Complaints | Median mi | Recalls | Crash ★ | MPG | Score (50 = typical) | Trend |
|---|---|---|---|---|---|---|---|
| 2003 | 56 | 57,500 | 2 | — | 18 | Not compared (before 2008) | Stable |
| 2002 | 123 | 60,000 | 3 | — | 18 | Not compared (before 2008) | Stable |
| 2001 | 78 | 59,750 | 2 | — | 18 | Not compared (before 2008) | Stable |
| 2000 | 51 | 57,171 | 3 | — | 18 | Not compared (before 2008) | Stable |
| 1999 | 23 | 86,450 | 2 | — | 18 | — | Stable |
| 1998 | 27 | 71,750 | 1 | — | 18 | Not compared (before 2008) | Stable |
| 1997 | 34 | 111,566 | 0 | — | 19 | Not compared (before 2008) | Stable |
| 1995 | 12 | 137,500 | 0 | — | 19 | — | Not enough data |
| 1994 | 27 | 50,015 | 2 | — | 19 | Not compared (before 2008) | Stable |
| 1993 | 29 | 108 | 3 | — | 18 | Not compared (before 2008) | Stable |
| 1992 | 42 | 120,000 | 2 | — | 19 | Not compared (before 2008) | Stable |
All Mitsubishi Diamante model years · Best and worst years by complaints
Frequently asked questions
What are the most common problems with the 2001 Mitsubishi Diamante?
Owners of this model year most often describe a coolant smell inside the cabin, windows that fog and will not clear, and a heater core that has to be replaced — usually in the 30,000 to 80,000 mile range and worse in cold weather when the defroster is used. The issues reported most often: Heater core leak (coolant smell, fogged windows); Engine cooling — overheating and coolant loss; Rear knuckle bushings worn.
How many NHTSA complaints does the 2001 Mitsubishi Diamante have?
NHTSA recorded 78 consumer complaints for the 2001 Mitsubishi Diamante as of Oct 30, 2026. Complaints are unverified consumer reports and may be duplicated or inaccurate.
What part of the 2001 Mitsubishi Diamante is reported most often?
Visibility is named most often, in 56 complaints (72% of the total), followed by engine cooling with 14.
Has the 2001 Mitsubishi Diamante been recalled?
NHTSA lists 2 recall campaigns for this model year. To check a specific vehicle, enter its VIN at nhtsa.gov/recalls.
What gas mileage does the 2001 Mitsubishi Diamante get?
The EPA rates the 2001 Mitsubishi Diamante (Diamante, 3.5L 6-cyl) at 18 mpg combined, 16 city and 23 highway, with an estimated annual fuel cost of $4,550 at 15,000 miles a year. Other engine and drive versions are rated differently.
At what mileage are problems with the 2001 Mitsubishi Diamante reported?
Among the 57 complaints that include a mileage, the median is 59,750 miles and the middle half falls between 45,000 and 75,000 miles; 37% were filed for vehicles with under 50,000 miles.
About this data. Data from NHTSA (ODI) complaints, recalls, TSBs and investigations, updated Oct 30, 2026. Complaints are unverified consumer reports and may be duplicated or inaccurate. Fuel economy is from the EPA and DOE (fueleconomy.gov).
Complaint counts come from NHTSA’s public complaint database; we count each complaint once. The source records for this vehicle are on nhtsa.gov. Scores and trends are our own summaries of that data, described in the methodology. This page is not legal, safety or repair advice: for a specific vehicle, check its VIN at nhtsa.gov/recalls and ask a qualified mechanic. See an error? Tell us.