1966 427/390 Thermostat failure

[Jerry S.]

Just noticed my water temperature gauge is not working. On a few earlier drives I notice the needle jumping back and forth erratically and then it would settle at about 180'. On my drive yesterday it didn't move at all, just stayed as if the engine was turned off. The car drove great but it was a short drive as I don't want to risk any damage to the engine. I'm looking for suggestions or directions to other posts on how to diagnose the issue and if necessary, find the correct thermostat replacement.

[Gary C.]

Re: 1966 427/390 Thermostat failure

Jerry,

Highly recommend you order the proper degree Robert Shaw thermostat. Robert Shaw thermostats are "safe" thermostats and fail open instead of closed.

Gary
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[Duke W.]

Re: 1966 427/390 Thermostat failure

Maybe it's a problem with the temp sender or the electrical connector, which you should check and be sure it's clean and making good contact. It's grounded through the connection to the manifold, so no sealer of any kind should be used. Also check the connection at the gage.

Before you condemn the thermostat use an IR gun to check actual temperatures along the top hose and radiator nipple. Hold it close because these devises measure an average of a cone and the farther away the less accurate the reading because it could average in background temperatures.

Duke

[Mark E.]

Re: 1966 427/390 Thermostat failure

The symptoms you describe (gauge not working) have nothing to do with the thermostat. Probably the gauge, its sending unit or the circuit between.

[Jerry S.]

Re: 1966 427/390 Thermostat failure

Thanks to all for contributing to my discover. The simplest fix in the world. Used an IR to verify temps within acceptable range. Then saw the little black sensor that was supposed to be attached on top of the manifold was not connected properly. Attached it and all is well.

Tried to send a picture as an attachment but won't let me upload and attach.