Engine thermostat jiggle pin
What’s the purpose of a thermostat jiggle pin?
The thermostat jiggle pin is a bleeder valve of sorts. The jiggle pin sits in a small hole in the top plate of the thermostat. When the thermostat is installed in a horizontal position, the jiggle pin should be located up, in the 12:00 position. That allows any air trapped in the system to bleed past the thermostat when it’s closed. If the jiggle pin is located in any other position in a horizontal installation, the air around the thermostat’s wax element would cause an air lock, preventing it from heating up and opening the thermostat valve.
©, 2021 Rick Muscoplat
Posted on by Rick Muscoplat