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2003 Mitsubishi Diamante Recalls, Problems & Maintenance

The 2003 Mitsubishi Diamante has no open NHTSA recalls. Owners report 5 recurring issue clusters, led by “Heater core coolant leak, odor and window fogging.” Mitsubishi publishes short, conservative intervals: oil every 7,500 miles normal / 3,750 severe, and — unlike many rivals — an explicit CVT fluid replacement schedule rather than a 'lifetime fill' claim. Read the severe-service column honestly: stop-and-go city trips, short hops, and hot climates all qualify, and they describe how most Mirages actually live. The 10-year/100,000-mile powertrain warranty stays intact only with documented on-schedule service.

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No open recalls on file. NHTSA lists no unrepaired safety recalls for this year, make and model. A recall can be issued at any time, and a specific car can still have one open — check yours by VIN at nhtsa.gov/recalls.

Known issues & problems for this vehicle

What drivers and federal regulators have officially reported about the 2003 Mitsubishi Diamante.

Reported to NHTSA

Heater core coolant leak, odor and window fogging

VISIBILITY

32 NHTSA complaints · 2005-02 → 2011-06

“HEATER CORE LEAKING CAUSING FUMES IN THE PASSENGER COMPARTMENT AND FOGGING OF THE WINDSHIELD”
— Owner report, NHTSA ODI #10156684
“AN ANTIFREEZE ODOR WAS NOTICED INITIALLY AND BEGAN TO INTENSIFY WITH TIME. WHEN THE DEFROSTER IS RUNNING THE WINDSHIELD WILL FOG UP AND THE ANTI-FREEZE SMELL IS SO INTENSE THAT IT NAUSEATES MY WIFE AND KIDS”
— Owner report, NHTSA ODI #10183423
“I NOTICED THE SMELL OF MAPLE SYRUP ABOUT TWO WEEKS AGO. TODAY, THE INSIDE WINDSHIELD AND SIDE WINDOWS OF THE DIAMANTE FOGGED UP WITH A GREASE FILM THAT WOULD NOT CLEAR”
— Owner report, NHTSA ODI #10187209

Read all complaints on NHTSA →

Heater core leak with transmission control failure

ENGINE AND ENGINE COOLING, POWER TRAIN

11 NHTSA complaints · 2006-04 → 2013-03

“I WAS TOLD THAT THE CAR'S HEATER CORE LEAKED ONTO THE COMPUTER WHICH CAUSED THE TRANSMISSION RELAY TO SHORT OUT DO TO THE COMPUTER FAILING”
— Owner report, NHTSA ODI #10224750
“THE MECHANIC SAID MY HEATER CORE WAS LEAKING COOLANT ONTO THE TRANSMISSION CONTROL MODULE CAUSING IT TO MALFUNCTION”
— Owner report, NHTSA ODI #10246914
“THE CONTACT STATED THAT THE HEATER CORE FLUID LEAKED ONTO THE CENTRAL COMPUTER AND CAUSED THE TRANSMISSION TO FAIL”
— Owner report, NHTSA ODI #10502674

Read all complaints on NHTSA →

Vibration and shaking when brakes are applied

SERVICE BRAKES, HYDRAULIC

8 NHTSA complaints · 2004-05 → 2006-04

“BRAKES VIBRATE WHEN APPLIED. I HAVE RETURNED MY '03 DIAMONTE FOUR TIMES FOR REPAIRS AND EACH TIME THEY STATE THAT THE ROTORS WERE WARPED AND EITHER REPLACED OR MACHINED THEM”
— Owner report, NHTSA ODI #10098895
“WHEN I APPLY THE BRAKES, THE CAR SHAKES AND JERKS UNCONTROLLABLY”
— Owner report, NHTSA ODI #10134166
“CAR SHAKES WHEN BRAKES ARE APPLIED. HAD BRAKES & ROTORS REPLACED AT 50,000 MILES”
— Owner report, NHTSA ODI #10155554

Read all complaints on NHTSA →

Tire air loss and tire failure

TIRES

3 NHTSA complaints · 2004-06 → 2019-07

“EAGLE LS KEEPS LOSING TIRE PRESSURE (ABOUT 10PSI) EVERY 5-7 DAYS”
— Owner report, NHTSA ODI #10098795
“WHILE DRIVING 25 MPH, AIR FROM THE VEHICLE'S FRONT DRIVER SIDE TIRE BEGAN TO BE RELEASED”
— Owner report, NHTSA ODI #11233933

Read all complaints on NHTSA →

Intermittent door lock and headlight electrical faults

ELECTRICAL SYSTEM

2 NHTSA complaints · 2005-04 → 2007-02

“CAR DOORS ARE LOCKING BY THEMSELVES, THE ALARM FOR KEYS BEING LEFT IN THE IGNITION NO LONGER SOUNDS, THE AUTOMATIC UNLOCK WHEN KEYS LEFT IN THE IGNITION NO LONGER WORKS, AND THE HEADLIGHTS DO NOT TURN OFF WHEN THE CAR IS TURNED OFF AND DOOR OPENED”
— Owner report, NHTSA ODI #10117995
“VARIOUS INTERMITTENT FAILURES TO INCLUDE, CAR LOCKING ON ITS OWN, HEADLIGHTS NOT GOING OUT WHEN CAR IS TURNED OFF, CAR NOT DINGING WHEN KEYS LEFT IN IGNITION, AND WINDOW FUSE BEING BLOWN WHEN WINDOWS ARE NOT BEING RAISED OR LOWERED”
— Owner report, NHTSA ODI #10182516

Read all complaints on NHTSA →

Issues on other model years

Source: NHTSA Office of Defects Investigation (ODI). Complaint data refreshed Sep 20, 2026. Investigation data refreshed Sep 20, 2026.

We display NHTSA's record with attribution; we don't editorialize on what these complaints mean for any specific vehicle.

Raw data + downloads for this vehicle →

Essential maintenance

Critical for safety and preventing major damage

Engine Oil & Filter

Every 7,500 mi

Replace every 7,500 miles normal / 3,750 severe. Mirage's 1.2L three-cylinder holds barely over 3 quarts — small sumps punish stretched intervals. 0W-20 on most recent models.

Estimated cost — typical U.S. ranges

Dealer

~$120–$160

Shop

~$85–$115

DIY

~$25–$55

Full synthetic costs more than conventional. 5-quart 0W-20 + filter is the typical bill.

CVT Fluid

Every 60,000 mi

Mitsubishi schedules CVT fluid replacement — commonly every 60,000 miles normal / 30,000 severe (check your year's table). Use only the specified CVT fluid (J4/CVTF-J4 family); generic ATF destroys the belt-and-pulley unit.

Estimated cost — typical U.S. ranges

Dealer

~$360–$500

Shop

~$255–$355

DIY

~$80–$180

CVT fluid is manufacturer-specific and pricey — do NOT substitute conventional ATF.

Tire Rotation

Every 7,500 mi

Rotate with every oil change. Light Mirages are easy on tires but the economy-focused OEM rubber wears fast when neglected.

Estimated cost — typical U.S. ranges

Dealer

~$85

Shop

~$60

DIY

Free

Often free at the shop where you bought the tires — worth asking before paying.

Brake Inspection

Every 7,500 mi

Inspect pads, rotors/drums, and lines at each service — Mirage G4 retains rear drums, which need periodic adjustment checks.

Estimated cost — typical U.S. ranges

Dealer

~$85

Shop

~$60

DIY

Free

Most shops do this free as a courtesy with any service. Don't pay separately if you can avoid it.

Brake Fluid

Every 30,000 mi

Replace every 2-3 years per the schedule. Cheap job, big ABS-unit insurance.

Estimated cost — typical U.S. ranges

Dealer

~$180–$200

Shop

~$125–$140

DIY

~$10–$25

DOT 3 or 4 — match the cap. Vacuum bleeders make this a one-person DIY.

Important maintenance

Keeps your vehicle running smoothly and efficiently

Spark Plugs

Every 60,000 mi

Iridium plugs commonly every 60,000 miles on the Mirage's 3A92 and Lancer's 4B11 — verify your year's table, as some engines list up to 105,000.

Estimated cost — typical U.S. ranges

Dealer

~$285–$390

Shop

~$200–$275

DIY

~$25–$100

Iridium plugs cost more but last 100k+ miles. V6/V8 access varies wildly — some are tough.

Engine Air Filter

Every 15,000 mi

Mitsubishi's schedule replaces the engine air filter every 15,000 miles — shorter than most brands, and a 5-minute DIY on the Mirage.

Estimated cost — typical U.S. ranges

Dealer

~$60–$95

Shop

~$45–$70

DIY

~$15–$40

5-minute job on most cars; the airbox lid usually has clips, no tools needed.

Drive Belt

Every 60,000 mi

Inspect from 60,000 miles and replace on cracking. The Mirage's single serpentine belt also drives the A/C — a failure strands the car's accessories at once.

Estimated cost — typical U.S. ranges

Dealer

~$195–$235

Shop

~$135–$165

DIY

~$20–$50

DIY-friendly if you can reach the tensioner. Inspect for cracks rather than swap on a strict mileage interval.

Recommended maintenance

Extends the life of your vehicle and improves comfort

Cabin Air Filter

Every 15,000 mi

Replace every 15,000 miles, behind the glovebox. Often skipped at quick-lube visits — worth checking if airflow feels weak.

Estimated cost — typical U.S. ranges

Dealer

~$60–$95

Shop

~$45–$70

DIY

~$15–$40

Usually behind the glovebox. Shops charge labor for a 10-minute job — easy DIY win.

Coolant Replacement

Every 60,000 mi

First change around 60,000 miles, then roughly every 30,000-45,000 per the schedule. Mitsubishi long-life coolant or equivalent OAT for your year.

Estimated cost — typical U.S. ranges

Dealer

~$285–$330

Shop

~$200–$235

DIY

~$25–$60

Use the manufacturer-specified coolant — wrong color/chemistry can damage the cooling system.

Battery Test & Service

Every 25,000 mi

Test annually after year 3. Small-battery economy cars have little reserve — the first cold snap finds a weak one.

Estimated cost — typical U.S. ranges

Dealer

~$225–$390

Shop

~$160–$280

DIY

~$130–$250

Most auto-parts stores test and install batteries free with purchase. Skip the dealer markup.

Fatal crash history & reported problems

Occupant deaths in fatal crashes (FARS)

25 crashes 1990–2024

How the 25 occupant deaths break down

15

driver deaths

10

passenger deaths

25

occupant deaths

Crash years covered: 1990–2024 This model year first appears in 2003 crashes. Older models have had more years on the road to appear in these crashes, so a higher count here does not by itself mean a vehicle is less safe.

FARS counts every occupant death in a fatal crash, whatever the cause — it does not mean the vehicle was at fault or defective. Counts are not adjusted for how many of each vehicle are on the road. How to read this number

FARS 2024 data is an annual report file. NHTSA revises these records when the final file is published, so this count can change.

Why we show driver deaths too

Every vehicle has exactly one driver seat, so driver deaths line up fairly when you compare one model to another. Occupant deaths include passengers, so a three row SUV can show a higher number than a two seat car simply because it carries more people.

Both figures are plain counts, not rates. A rate would need to know how many of each vehicle are on the road, and that registration data is not public, so we do not publish rates or scores of any kind.

IIHS publishes driver death rates using this same driver only idea, paired with a registered vehicle years denominator we do not have. Their rates and these counts answer different questions, so do not read either number here as a safety rating.

Owner-reported problem signals

Separate from the federal fatality data above: complaints owners filed with NHTSA about this year and model. These are reports of problems, unverified, and are counted here only as signals.

3

complaints mentioning a crash

0

complaints mentioning a fire

Reviewed known issues for this vehicle

Typical U.S. ranges. Actual quotes vary by shop, parts choice, and vehicle condition.

How we estimate: Dealer = OEM parts × 1.4 + labor × $165/hr. Shop = parts + labor × $115/hr. DIY = parts only.

This maintenance schedule for the 2003 Mitsubishi Diamante reflects Mitsubishi's published service intervals. Your actual service needs may vary based on driving conditions, climate, and vehicle usage. Always consult your owner's manual for model-specific recommendations.

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