One problem related to manifold/header/muffler/tail pipe has been reported for the 2006 Toyota Highlander. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 Toyota Highlander based on all problems reported for the 2006 Highlander.
When I was driving on the interstate about 75mph the temperature gauge rose above the read line (hot). Before I was able to get to a parking area it continuously rose and fell, however, it never dropped as low as the middle line on the gauge. After checking the fluids I had to add water. I took my Highlander to a mechanic and they told me that the intake manifold was cracked and was leaking coolant($700 to repair this). I had this fixed and had not taken it out of town until Apr 27, 2013 and the same thing happened again. Took it to Toyota and they told me that the threads were stripped and the bolts were coming out "the head is pulling away from the block and coolant is leaking. I take very good care of my vehicle and have every receipt for oil changes and maintenance. I was told that I may need a new engine ($6000 to fix this) and am concerned that this is happening to a lot of people with this type of car. Coolant is dangerous to humans, animals, and the environment so this can be a safety concern. Toyota needs to take responsibility for this error I am very frustrated and Toyota is not going to do anything about it. I know I am not the only one with this issue with this Toyota and they have lost a loyal customer over this. This issue is obviously happening more and more everyday and it is frustrating. Any advise is welcome!!!.