I am building a 24 hrs of Lemons car out of a 83 RX7 and it came to me somewhat disassembled. The Lemons team i am on already has a 82 RX7 that we have been racing and when we got it it already was built and came with "parts". One of the parts is a radiator which the 83 did not have so have installed and i am getting ready to run the engine this weekend after the new gauges arrive (other item that are missing) and the threaded hole is a mystery to me.
So does anyone know what is for otherwise I will just plug it.
Oh it is on the top of the radiator.

 

coolant level sensor is supposed to go there

 

The coolant level sensor is available still. You can pick one up for under $20. Be sure to also get the rubber gasket. Some do not come with the gasket.

 

Thank you everyone, I will be ordering today

 

You mention new gauges, will the Lemons car retain the original dash warning lights?

If not, you wont have an indication from the sensor, and will need to wire something up yourself to get an indication.

Probably helpful to have in Lemons. Will show you a cooling system leak/problem sooner than it running hot or overheating I think.