Mechanical temp gauge going bad??

[napa68]

After getting my 67 Nova running again, I am having trouble with the SW mechanical temp gauge jumping ALL over the place...............like from 160 to 200 in a matter is a few seconds and then settling back down. Only to jump around a little more (perhaps not quite as drastic). I have checked block and cylinder head temp with a temp gun and the temp seems to be stabilized as well as consistent. Additionally, I have checked the coolant for hydrocarbons and that is clear (bad head gasket). The system has been burped so that is fine.

I am not sure if I pinched the capillary tubing while working on the car? Any similar experiences or advice? This is an NOS gauge that has been in the car for around 7 years and the engine has never exhibited this type of behavior.

Thanks,

Tim

[TDW]

Thermostat is most likely sticking.

[Plowman]

I put a 1/8" in all my thermostats but the "HOT SET UP" is a EPM/Stewart High-Flow Thermostat and they also have three 3/16 machined bypass holes to allow some coolant through even when closed-perfect for high--rpm engines too.

[Salvatore]

I would try another gauge Napa. See where that takes you.

[69VN]

Check to see if you have enough coolant in your radiator if you have already done all of the above!