It's located at the top of the head above the plugs.
4 screws and it's off.
Be VERY carefull when removing.They've been there for a very long time and are probably stuck.
I tap them and spray PB.Blaster and tap and spray.
Then try to remove.
If you can touch the side of the head and not burn yourself the thermo is probablt working.
Now where is the tell tale hooked up?
It's probably hooked to the top of the head.
The hottest part of the motor.
It has water circulating from the top of the pistons and through the tell tale.
So it's gonna be hot.
To tell if it's too hot,make sure the overheat alarm is working.
On the head is a thermo switch.
Key on and ground out the switch.
A piece of wire bare on both ends.
Touch the post on the switch and any bare spot/screwhead on the motor.
It should make the buzzer sound off.