One problem related to coolant leaking has been reported for the 2006 Nissan Altima. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 Nissan Altima based on all problems reported for the 2006 Altima.
I had coolant service and after that I started experiencing low levels of coolant which led to overheating of car. I kept getting the car check to find out if there were leaks. I checked recall notices and then was told I needed sensors. I called Nissan in September and was told out of the 653k cars mine was not affected! I find that hard to believe. I then had sensors replaced (crankshaft and speed) . Now I'm being told head gasket blown and engine needs replacement. The recall from Nissan says there we engine cooling problems.