Drilling into thermostat

[RangerThings93]

Here I am watching this video on how to apply RTV silicone to the thermostat housing and towards the end of the video of the guy says he drills into the thermostat for a variety of reasons. Is this actually a thing?



I'm replacing mine on my 93 Ranger today. Just something I haven't heard of yet.

 

[scotts90ranger]

Yes, it is a thing. Some thermostats will have a little brass wiggler thing that will bypass air but should restrict fluid. At work we build engines and in some we drill the thermostats with an ~1/8" drill bit which helps the filling/bleeding process and doesn't change how the thermostat works enough to worry about. The reason for this is as you are filling the cooling system the air wants to go up, if the flow path is dead ended at the thermostat and any bypass (like heater plumbing) is lower than the thermostat there is going to be an air pocket behind the thermostat and the wax pellet thing can't sense the temperature of the coolant so will not open, having an internal air bleed lets the thermostat get to the coolant.

 

[Curious Hound]

 

[Sharky]

scotts90ranger nailed it ​

 

[RangerThings93]

Thank you

Yes, it is a thing. Some thermostats will have a little brass wiggler thing that will bypass air but should restrict fluid. At work we build engines and in some we drill the thermostats with an ~1/8" drill bit which helps the filling/bleeding process and doesn't change how the thermostat works enough to worry about. The reason for this is as you are filling the cooling system the air wants to go up, if the flow path is dead ended at the thermostat and any bypass (like heater plumbing) is lower than the thermostat there is going to be an air pocket behind the thermostat and the wax pellet thing can't sense the temperature of the coolant so will not open, having an internal air bleed lets the thermostat get to the coolant.

Oh nice, thank you for explaining that. Do I need to apply RTV silicone on the housing before I put my new thermostat in?

 

[Jazzer]

Not if both surfaces are flat and you have a gasket or o-ring.