30th Oct 2008, 22:34

I have a 2003 Mitsubishi Diamante, and I could smel anti-freeze at about 70000 miles. My wife drives about 500 miles a month. It now has 169,000 miles and has been sitting for about 7 months, because the transmission will not act right. My car has all the same problems as you guys. I guess it was not a bad idea when I buy my 2005 Maxima 7 months ago. Will fix myself. Wish me luck.

9th Nov 2008, 12:15

I have a 2003 Diamante with 69000k. When I uncapped the radiator to check the coolant level it was down slightly so I topped it off with water. Since then, we've noticed water on the inside of the windshield around the middle. Any thoughts?

13th Nov 2008, 02:00

I'm about to purchase an '02 Diamante LS with 122k miles, but these repeated tales of heater core problems are scaring the heck out of me. How best to tell if the car I'm interested in will have this problem, or perhaps has had the problem? Do ALL Diamantes have this problem? Does anyone know what percent of Diamantes have experienced the heater core malfunction?

13th Nov 2008, 18:02

Regarding how to tell if vehicle has the heater core problem:

1. Take it for an extended test drive with the heater turned up high on front windshield defrost setting. Check for a "burnt maple syrup smell" coming out of the ducts, and for fogging of the windshield.

2. Check the carpet around the passenger side foot area near firewall. The heater core is located directly above that area. Touch for wetness and smell for presence of anti freeze leaking.

3. Finally, have a mechanic go through this check and the rest of vehicle thoroughly for other possible surprises!

Don't know how to predict if this vehicle will ever experience the problem, but most likely if it was going to happen, it already has. Most of the heater core issues occur before 100k miles. Ask the seller for full disclosure of past repairs and maintenance performed. If they can't or won't, walk away. Also, definitely get a carfax on the vehicle to check for owner history, odometer reading anomolies, accidents, salvage, or rebuilt title.

I own a 02 Diamante VR-X with 94,000 miles, and had the heater core issue showed up at 85,000. I replaced the leaking heater core pipe gaskets ($2.50 total cost) myself and saved $1,000. Most people I suspect have to pay a shop to do it.

Good Luck!

16th Dec 2008, 18:30

I've attempted to replace the O-rings myself with the instructions linked earlier (going through the glovebox and behind the console) but have come to a stopping point.

Do I have to empty the freon (or whatever they use now) or anything before messing with the evaporator? I don't know much about A/C units so I'm hesitant to mess with it. Anything is better than the cost of this repair though. I have the o-rings ready to go. Thanks, if someone sees this.

17th Dec 2008, 16:19


I have a 2003 VR-X with 106K miles on it. Replaced the heating coil and seems to be working fine. However, yesterday when I went to drive it the TCL Off light came on with the Service Engine Soon light. Can anyone tell me why this is happening? I will not buy another Mits... to expensive to fix and I have already dumped in over 2500.00 for this car in about 2 months... goodness knows what the TCL is going to set me back.

I bought the car brand new and it is five years old now, but no wonder why they do not make this model any more...

Need some guidance.

Thank you.

18th Dec 2008, 20:55

Regarding freon (actually R134) removal from A/C system to replace the heater core o-rings: Yes, you need remove the R134 from the system, in order to disconnect the two A/C evaporator lines that connect to the fire wall from the engine compartment side (see on line instructions). This will allow you to remove the evaporator from inside the car behind the glove box. You need to remove the evaporator in order to get access to the heater core pipes (inlet and outlet) for replacing the gasket on each pipe. I took my VR-X to a local shop and they removed the R134 (and replaced it later) for about $35. You're almost there, keep going! You're be glad you saved $1,000 by doing it yourself. The online instructions are actually very good. The space is pretty tight to work around the heater core pipes, but its doable.

18th Dec 2008, 21:09

To the 03 VR-X owner with TCL and check Engine Light:

Unfortunately this is one of the other problematic issues with this generation of Diamante besides the poorly designed Heater core piping. The best thing is to find out why this fault was set by going to a local shop and have them run a diagnostic scan for the codes. On my 02 Vr-X I had the TCL and ABS light come on and off intermittently along with the ABS controller acting funny when the brake was depressed. I did the diagnostics myself on the ABS system and found that the right rear ABS wheel sensor was bad. Dealer wanted $400 for the sensor (not including labor), I said forget it. Found a late model Diamante in junkyard, took off sensor, installed it on mine and problem went away. All for $150.

If you get the codes from the scan and report back here, I'll tell you what they mean and the action to take to remedy. I have access to the 1999-2004 Diamante shop manual.

Good luck!

25th Dec 2008, 14:39

Does anybody know if the antifreeze will leak to the passenger side onto the carpet, or is it coming from underneath? I had the heater core problem a year ago and Mitsubishi repaired it for $1100 (they said they only had to replace the O-rings) the rest of the charge was labor.

The other day I was cleaning inside of the car and the passenger side carpet was soaked. However I keep plastic mats on top of the carpet and did not have anything on them. I used paper towels to try and soak it up. The water looked like a diluted green but had no smell.

I do not get any smell in my car, but I do get water buildup on the windshield whenever it is humid out.


28th Dec 2008, 11:27

Where does the antifreeze actually come from? My floor mats are soaked with it but it doesn't drip from above. If I could get away with just replacing the O-Rings as mentioned by a few, I would really like to try. Can you access the heater core through the glove box?

31st Dec 2008, 13:59

If your carpet is soaked on the passenger side up by the firewall, has a greenish color residue, and smells like burnt syrup, it is most certainly from the leaking heater core pipe gaskets, which are right next to the firewall above the carpet liner. It's usually a slow leak, so you don't notice the wet carpet until you start smelling the antifreeze and/or see your windows fog up periodically.

It's the gaskets that cause the leak on either or both the inlet and outlet heater core pipes that connect the to the coolant lines at the fire wall. The replacements gaskets (improved design) can be obtained at the Mit. dealer for about $3. It's possible to replace them yourself if your handy, have basic shop tools, and patience. There's a procedure that was posted a few years back that explains step by step how to do it (see below). I used it myself this past year and it is spot on. It took me about 6 hours, mostly because I was very careful and took my time. It does NOT require complete removal of the instrument panel, as the Mit. shop manual says. That's why the dealers / shops charge you $1000+ due to the extreme labor. You can get to the heater core pipes by removing the glove box, trim pieces, evaporator, some brackets and wiring. It's a tight fit, but certainly doable.

Here's link to the procedure:


Good luck! Marco in Indy.