I too have replaced the heater core on my 2003 Diamnate VRX at 65,000 miles. Also, timing belt. Now the transmission has gome out at 87,000 miles. I wonder if there is something to the tip that perhaps the radiator fluid leaked on to the Transmission Control Unit? I like the car but I should not have to replace a transmission on a car with less than 100,000 miles. Mtsubishi? Never again.
I too have had to replace the heater core and replaced two transmissions. The car is a very beautiful looking car, but there are numerous problems that should not occur less than 100,000 miles. I am just hitting 68,000 miles and these problems are happening. I would NEVER purchase another Mitsubishi again!