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really awful
Crashes / Fires:
0 / 0
Injuries / Deaths:
1 / 0
Average Mileage:
52,434 miles

About These NHTSA Complaints:

This data is from the NHTSA — the US gov't agency tasked with vehicle safety. Complaints are spread across multiple & redundant categories, & are not organized by problem.

So how do you find out what problems are occurring? For this NHTSA complaint data, the only way is to read through the comments below. Any duplicates or errors? It's not us.

2002 Mitsubishi Diamante cooling system problems

cooling system problem

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2002 Mitsubishi Diamante Owner Comments

problem #16

Apr 302010


  • miles


Mitsubishi Diamante 2002 has faulty O-rings and is widely publicized to cause major heater core problems and anti-freeze leakage.

- Medford, MA, USA

problem #15

Jul 012005


  • 37,000 miles
Our 2002 Mitsubishi Diamante vr-X has been misting from the heater core for a few years. The problem is bad gaskets (O-rings) that join the heater core with the lines for the heater hoses. The heater core is installed right over the PCM unit. If it leaks badly enough, the PCM and transmission relay will be destroyed. It (heater core) failed shortly after the warranty expired and when we went to Mitsubishi dealer, they refused to fix it. They quoted us $1400 for repairs. On the internet, there are hundreds of complaints for the same problem, but no one has gotten any satisfaction from Mitsubishi. I put some radiator stop-leak in and this seemed to help somewhat, but it is starting to mist again with anti-freeze in the passenger compartment. This is a toxin and is dangerous to inhale and will jeopardize my family's health.

- Natrona Heights, PA, USA

problem #14

Aug 012001


  • 78,000 miles
My 2002 Mitsubishi Diamante has O ring failure in the heater coil. I have read many complaints that this is common on this model and would like a recall on these vehicles due to the extreme nature of the issue. With the failure of the O rings come potential anti freeze vapors entering passenger compartment and causing physical damage to all passengers. It may also cause the car to overheat in the middle of heavy stop and go traffic and cause accidents and/or death. It may also cause the heating element to no longer work and passengers in the extreme winter climates may be susceptible to physical harm or death. Lastly, this is a rampant known issue with these vehicles and should be corrected at dealer cost. My car cost originally $30,000. And I would expect the american government to make these companies back up the vehicles they are selling to the american public and make them safe and worth the money that is spent on them.

- Semmes, AL, USA

problem #13

Apr 112006


  • 71,000 miles


Heater core leaks into car steams up windows and leaks on the computer and changes the transmission shifting.

- Oconomwoc, WI, USA

problem #12

Feb 252009


  • 103,000 miles
It happened out of no where. No signs or warnings to help prevent this problem. The heater core leaks uncontrollably. It's a long labor job and happens pretty early in the cars life spans. The parts are cheap to replace but the consequences are drastic.

- Orlando , FL, USA

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problem #11

Aug 302008


  • 60,000 miles
At approx 60K (I am the original owner) the car began to emit mist from the vents. The first incident was a near overheating event which caused me to check the coolant. After topping off the level the car operated normally for a few months and then repeated the behavior. The tcl went off, the check engine light came on, the mist got heavier, and the car is a danger to both myself as an operator and others on the highway because the fog from the antifreeze damages visibility. The floor mat on the passenger side has also gathered moisture from the apparent leak. This scenario is well documented by others and demands a recall.

- Stockbridge, GA, USA

problem #10

Nov 152007


  • miles


Heater core failure caused failure of power control module. Total repair bill > $2,500. Mitsubishi is fully aware of the problem and neglects to even inform customers that there are steps that can be taken to remedy the problem before a costly breakdown. Defective PCM causes severe drivable problems.

- Clifton, VA, USA

problem #9

Jan 012007


  • 70,000 miles
At about 70,000 miles I started to see a very fine mist-like smoke coming from the dash while driving. There were no warning lamps illuminated on the dash. So after the temp gauge started to go up and I could also smell anti-freeze. I checked the radiator area and could find no leak but when I checked the coolant it was low. I topped off the coolant and a couple of months later it did the same thing. I then added stop-leak and the coolant level seems to be staying but I can still smell the anti-freeze and the windows fog up. I understand there is an issue with gaskets on the heater core. I am worried the coolant leaked into my vehicle in the area of the ECM. To me, this is a serious safety issue and Mitsubishi should be correcting this problem because it is very common from what I have read on-line.

- Hugo, MN, USA

problem #8

Sep 232008


  • 75,000 miles
I bought a 2002 Mitsubishi Diamante ls 10/3/07. He had 53,000 miles on it. It now has about 75,000 miles. My problem is the same as hundreds of owner of this car. Heater core issues. I recently had the heater core gaskets replaced as I was told that the heater core was ok, still had to pay for labor. It is now leaking again. This is a very common problem and seems that mitsubushi is unwilling to do anything about this. The heater core is right above the computer that runs the car. When the heater core goes bad, its leaks on the computer. What kind of sense does that make? my engine light is constantly on and I have seen the tcl light come on as well. I have searched the internet and all 3 of these problems are very common. I want to know if there is anything that can be done about this or if mitsubushi has addressed the problem and I am not aware of. I cannot afford to fix the car or get a new. Please help!

- Turtle Creek, PA, USA

problem #7

Jan 302008

Diamante 6-cyl

  • Automatic transmission
  • 80,000 miles
I found postings of the same heater core issue. Windshield fog and the awful syrup smell of anitfreeze. There needs to be a recall as you can clearly see the history of complaints dating back to 1995 or earlier. Please look into this urgent matter.

- Melbourne, FL, USA

problem #6

Mar 282006

Diamante 6-cyl

  • Automatic transmission
  • miles


Heater core defective and leaked coolant underdash on to transmission ECM and neutral safety switch. Because of this very common manufacture defect I had to have my heater core, transmission ECM, neutral safety switch replace. And my transmission rebuild, none of which were warranted by the manufacture and were not cheap.

- Mineral Wells, TX, USA

problem #5

Dec 052007

Diamante 6-cyl

  • Automatic transmission
  • miles
Heater core leaking into passenger side of car, releasing coolant vapor into car cabin.

- Austin, TX, USA

problem #4

Apr 042006

Diamante 6-cyl

  • Automatic transmission
  • 55,000 miles
Recently the windows keep fogging up in my 2002 Mitsubishi Diamante. I have found through complaints with you and other internet sites that this is a common complaint and very expensive to remedy. Is there nothing being done by nhsta to make the manufacture fix this dangerous problem? every day it gets worse. So far I have not noticed a coolant leak, but from what I have read, it is forthcoming is a very dangerous problem that needs to be solved!!

- Pueblo, CO, USA

problem #3

Feb 192007

Diamante 6-cyl

  • Automatic transmission
  • 53,941 miles
Leakage of antifreeze ( engine coolant) into the passenger compartment of vehicle. The coolant smell was apparent within the car.

- Phoenix, AZ, USA

problem #2

Jan 232007

Diamante 6-cyl

  • Automatic transmission
  • 77,000 miles
Heater leakage from faulty seals, complained of headache for 3 weeks as soon as leak was discovered and fixed headaches have been gone.

- Old Forge, PA, USA

problem #1

Jun 262006

Diamante 6-cyl

  • Automatic transmission
  • 79,000 miles
This is the second time I am complaining about the same problem. The end of June 2006 I drove to work and reached down to pick some stuff up off the passenger side floor mat. It ended up being soaked. At first I thought some water had come in because the past few days our area had torrential rains. When I got home the next day I took up the floor mat to dry it out and notice all the liquid under it was greenish yellow. In my mind I went crazy because the same thing had happened to me a year and 2 weeks earlier. Once again the heater core became faulty and poured the engine coolant into the passenger spaces. Wonderful, since my wife was 8 months pregnant, great for her to be breathing those chemicals. I have to say I was fortunate that it didn't leak on any of the computer components, like has happened to others, especially while I was driving. Would have definitely caused a safety issue. It just blows my mind that I have had to pay for the same service twice in about a year, on a car that has less than 80,000 miles on it. I really hope the NHTSA looks into making this a recall issue, because it is just happening to too many consumers. Just imagine all those people who don't even know they can file a complaint. Yes, I know there were no deaths or injuries in my case, but when the coolant leaks on the computer brain of the car, it could become a real issue if driving on the highway or navigating crowded streets in town. The power stearing or antilock brakes would shut down if the computer crashed from getting wet.

- Annapolis, MD, USA

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