I had my local mechanic do my 90,000 mile service for me. They did the standard service plus a thermostat plus the heater tubes. They said everything looked great and probably didn't need to be replaced for a while except for the heater tubes! They had it all in a box for me to take home but I just wanted the heater tubes as a spare and the thermostat. I would have never known of the issue without this site. Thanks Mud!!