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

by in Whitlash, MT on April 15, 2013
2 answers 1 comment
ANSWER by on April 15, 2013
thermostat might be sticking and sound like you need a brake job make sure you check the calipers
ANSWER by on April 16, 2013
ck for coolant leak and coolant level to start with
COMMENT by on April 16, 2013
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