Hi... followed the entire debacle about the overheating, etc. with much interest, since my '04 FX35 with 110,000 is following a similar pattern. So far dealer has replaced a supposedly stuck thermostat, checked for exhaust gas contamination, flushed system, pressured checked, and declared everything good as new. 2K miles later overflow reservoir is almost full again, and gurgling sounds coming from behind the dash. Oh... and no overheating according to engine temp gauge. I have the feeling I'm heading down the same road you have recently travelled. Wondering, was the $3600 repair the Infiniti price, or from a private garage/mechanic? Thanks for sharing your painful experiences. Hope the new parts have made your FX better than new.
Regards,
Ron