I have an '07 Executive with 10K miles on it, and I find that I cannot tell if the coolant is low by using the port behind the front wheel. The port is about 1 1/2 inches high, and the tube that should show the coolant level is occluded. The bottom half is kind of white, and the top half is dark. The coolant level can't be seen even with a powerful flashlight. I filled the tank and over filled it. No change in the coloration of the port. So, my question is does anyone know if the lack of being able to see the coolant level is a general deterioration of the plastic tube in the port. Or might I have another problem. There is no overheating or change in the general temp gauge. I appreciate any insights. Hawk