Is it a new thermostat?
What is the make and part number?
It may start to open at 160 degrees and is fully open at 180 degrees.
If you have in sitting at idle on a hot day - does it hold steady at 180 degrees?
If you drive it long distances on a hot day - does it hold steady at 180 degrees?
An original-specification thermostat was rated to start opening at 140 degrees and would be fully open at 170 degrees.
1937 specifications
