Thermostat issue

[leelee27]

Please help on my way to work my gauge kept rising to mid range and then would go back down to low range. It did it the whole commute. Any ideas on what the problem is?

 

[FR-425]

This is normal.

In colder weather the engine will heat up until the thermostat opens.

When it does the cool water "coolant" in the radiator flows into the engine.
(the gauge drops)

Then the thermostat closes.
(the gauge begins to rise)

Reaches thermostat temp and the cycle repeats.

In hot weather the thermostat does the same thing but the temp variation is not as noticeable.