Most common 1998 Mitsubishi Diamante problems
Share of the 27 complaints; one complaint can involve more than one system. "~" is the median mileage when the problem started.
Mitsubishi Diamante complaints by model year
Best Diamante years: 1995, 1999, 1998. Years to avoid: 2002, 2001, 2003, 2000. Compare all years →
1998 Mitsubishi Diamante recalls (1)
Equipment › Other › Labels
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 the size requirements of the standard.
Remedy: Mitsubishi caribbean will mail a customer notification letter containing a written description and a graphic of the bi-lingual dashboard air bag warning label.
What 1998 Mitsubishi Diamante owners say
A/C & heater
This is a Mitsubishi Diamante 1998 es. 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. I am filing this complaint to ascertain that this is a very very common problem in Mitsubishi Diamante and Mitsubishi motors should be aware of three main risk associated with this: (1) the defect exposes customers to unusual level of toxic ethylene glycol which should not exceed 10-25 ppm levels (consult msds for ethylene glycol) (2) the leak can affect the car's microprocessor and poses a severe hazard for drivers. (3) faulty heater core makes the visibility difficult due to fogging of wind shield thus putting the driver at greater risk. …
I own a preowned 1998 mistubishi Diamante ls. When the climate control, particularly the heater is engaged, the smell of anti-freeze becomes quite apparent. Dealer claimed 2 years ago when I bought it that it was the smell of the chemicals used to clean the car during "make-ready." ethylen glycol fumes are toxic and this is a reoccuring defect in this model car from posts I have seen on various websites. I was later told that to fix this problem will cost close to $1000 since the car is out of warranty. Mitsubish issued a TSB addressing this problem, obviously they are aware of it. In addition, the windshield is covered with a film that cannot be washed off from this leak. A recall should be issued for this problem, I am not the first person to file this complaint on your website. Thank you.
Windows, wipers & sunroof
The heater core has failed (once again) I am not sure of any company that has realeased their cars with such a major failure without taking some kind of responsibility to recall this item in the car. Nearly all of the heater cores from Mitsubishi diamantes that I have seen are all bad. Leaks onto the ECU and causes a whole heck load of problems. Please dot have Mitsubishi recall this. As to this causes immense damages and people like me driving around with this faulty piece are breathing in the fumes and driving with nearly full fogged windshields causing really poor visibility which is an extreme hazard to our roads and fellow pedestrians please I urge you to take this complaint serious and use your dot powers to make this manufacturer do what is right! Thanks for your time
I own a preowned 1998 mistubishi Diamante ls. When the climate control, particularly the heater is engaged, the smell of anti-freeze becomes quite apparent. Dealer claimed 2 years ago when I bought it that it was the smell of the chemicals used to clean the car during "make-ready." ethylen glycol fumes are toxic and this is a reoccuring defect in this model car from posts I have seen on various websites. I was later told that to fix this problem will cost close to $1000 since the car is out of warranty. Mitsubish issued a TSB addressing this problem, obviously they are aware of it. In addition, the windshield is covered with a film that cannot be washed off from this leak. A recall should be issued for this problem, I am not the first person to file this complaint on your website. Thank you.
Speed control & acceleration
We just cleared canadian customs at blaine wa, pacific crossing, and were accelerating to speed limit on I 5 freeway when the car accelerated to near 100 miles an hour. The tach at some point was 7500 and increasing. The accelerator was stuck and eventually we were able to get to the emergency lane area and turned of the ignition key. Full pressure on the brakes would not slow it down much. We were towed 21 miles to davis automotive in bellingham, wa, where a replacement throttle cable and associated structure was severely bent and the cable had cut thru it and stuck. The consumer had the vehicle towed where a replacement throttle cable was installed. Updated 10/10/08.
This is the second time since December 2003 that the accelerator stuck while in reverse and the brakes failed, causing property damage and injuries. This is very dangerous and I thank god that no little kids were killed!!! The first time it happened I called Mitsubishi and reported the problem and never got a response.
1998 Mitsubishi Diamante engines & fuel economy
| Engine | Transmission | Drive | MPG city / hwy / combined |
|---|---|---|---|
| 3.5L 6-cyl | 4-speed automatic | FWD | 16 / 23 / 18 |
EPA ratings. Class: Midsize car.
Frequently asked questions
Is the 1998 Mitsubishi Diamante a good car?
Based on 27 owner complaints filed with NHTSA, the 1998 Diamante rates better than average: 53% fewer complaints than a typical year of the Diamante at the same age. It is one of the best Diamante years by this measure. Complaint counts don't account for sales volume or individual maintenance, so have any used car inspected before buying.
What is the most common problem with the 1998 Mitsubishi Diamante?
The a/c & heater — 14 complaints, 52% of all complaints for this model year, most often about defroster/defogger/hvac system › heater core. Next are the windows, wipers & sunroof (3) and speed control & acceleration (3).
How many recalls does the 1998 Mitsubishi Diamante have?
There is 1 recall for the 1998 Mitsubishi Diamante, the most recent from September 1, 2004 (labels). Recall repairs are free at any authorized dealer — check whether yours has been done with the VIN recall check.
What are the best and worst years of the Mitsubishi Diamante?
The best years by complaints, compared at the same age, are 1995, 1999 and 1998. Years to avoid or approach with caution: 2002, 2001, 2003 and 2000. See the full Mitsubishi Diamante years comparison.
At what mileage do 1998 Mitsubishi Diamante problems happen?
The median mileage reported in complaints is about 74,000 miles; 8% of problems with a recorded mileage started before 50,000 miles.
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.