Hello everyone,

Just received a new AC Delco thermostat for my 08 H3 (5cyl).

Upon picking it up I noticed a metallic clinking sound coming from the unit. Occurs when lightly shaking the part, cant tell whats causing it.

Is this normal? This is my first experience with a thermostat swap.

Thanks,
4WDIY

 

Most likely that would be the Jiggle Pin or Bleeder Valve you hear. The thermostat jiggle pin is a pin that is located in the small hole in the plate valve of the thermostat and which should always be in 12 o’clock position during installation. It helps bleed the cooling system of trapped air by allowing air to pass into the radiator, after which it can be released from the system. The jiggle pin is a big help in bleeding air when filling an empty cooling system. The hole prevents the formation of an air lock when the valve is closed. Mind that these types of thermostats should therefore always be positioned so that the jiggle pin is located on the top side of the valve. After all, only this twelve o’clock position will allow trapped air to escape.

It should be noted that not all thermostats have a jiggle pin. Some thermostats have a bleeder valve instead, which is located either directly in the thermostat housing or in the coolant hose going to the heat exchanger or to the expansion tank

 

Thanks TAINTER for the quick reply!

Makes sense. I noticed the sound is coming from a hole in the top of the part. There is a pin or ball bouncing around in there.

 

Bleeder Valve