Fluctuating thermostat

[brianmfournier]

I'm stumped here. Around town my thermostat reads normal, the car warms up and it sits halfway with normal driving. When I get up to highway speeds, the thermostat drops to the "C" and sits there until I get off of the highway again. Any ideas?

[Tugboatguy]

I'm stumped here. Around town my thermostat reads normal, the car warms up and it sits halfway with normal driving. When I get up to highway speeds, the thermostat drops to the "C" and sits there until I get off of the highway again. Any ideas?

Sounds like it's stuck in open position, your thermostat constantly adjusts the amount of coolant that passes through it to maintain operating temp. At highway speeds there's so much airflow thru the rad the coolant temp drops and the thermostat closes enough to maintain its temp setting, if it's suck open the engine will run cold at highway speed, not something you want to do a lot of it's bad for the engine.Suggest you get your thermostat checked/replaced.