My temp gauage keeps fluctuating when I drive on highway. on 2004 Ford Freestar

When I drive around town its ok but on highway it goes up and down quite regularly. Also when I reverse I hear a grinding sound coming from rear passenger side wheel. Please help

Asked by for the 2004 Ford Freestar
2 answers 1 comment
thermostat might be sticking and sound like you need a brake job make sure you check the calipers
ck for coolant leak and coolant level to start with
I have checked both and they areboth fine. When I set the interior temp to medium to low the temp stays low and doesnt fluctuate. What could the issue be