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.

 

[scotts90ranger]

Yeah, what Jazzer said, a smear doesn't hurt but "shouldn't" be necessary...

 

[PetroleumJunkie412]

"shouldn't" be necessary

*laughs in jeep 4.0*

 

[scotts90ranger]

the gasket on my 2.3L is leaking too, more of a seep, not fast enough to worry about, I'll get to it, I'm just happy the thermostat is working right so I don't really want to touch it...

 

[lil_Blue_Ford]

I put a smear of RTV on the thermostat housing. It’s not supposed to need it, but after having not done it and having a leak, yeah, I’ll give it a little help

 

[sgtsandman]

One thing that wasn't mentioned about the air bleed hole. If the thermostat sits at an angle (not all of them do), put the bleed hole on the up hill side so air has the best chance of escaping from under the thermostat.

As far as the RTV, I've never had to use it, but it won't hurt using it either as long as you don't go crazy. A little oozing out around the seam ensures a good seal. A lot oozing out the seam means that same amount is also probably oozing inside. Which could break off and clog something in the system, like a valve, heater core, or radiator, or even the thermostat itself.

 

[RangerThings93]

One thing that wasn't mentioned about the air bleed hole. If the thermostat sits at an angle (not all of them do), put the bleed hole on the up hill side so air has the best chance of escaping from under the thermostat.

As far as the RTV, I've never had to use it, but it won't hurt using it either as long as you don't go crazy. A little oozing out around the seam ensures a good seal. A lot oozing out the seam means that same amount is also probably oozing inside. Which could break off and clog something in the system, like a valve, heater core, or radiator, or even the thermostat itself.

Great tip, thank you