Someone school me on expansion tanks

[X3FBrian]

I'm kind of confused here about the expansion tank on my car. I just drove it an hour home (50 degrees out, interstate ride home) and I got home, checked all my fluids like I do from time to time. I opened the expansion tank cap, and the coolant in the tank is COLD.

Does the fluid not circulate through the cooling system to and from that expansion tank? I have aeroforce gauges and it never got above 180* temps, it hovered between 172-180*. I have the on 3 t-stat relocation to the top of the radiator, a 3 core fluidyne radiator, and the car is running great. Not down on power or anything.

The radiator and t-stat housing are hot to the touch. I squeezed the lower radiator hose, and the upper radiator hoses, and the coolant moves around in the expansion tank.

I'm not understanding this.

 

[DSG2003Mach1]

It’s just extra capacity, coolant does not travel through the tank as part of the flow path. If the system gets warm enough then as the coolant expands it may push some up into the tank

 

[X3FBrian]

It’s just extra capacity, coolant does not travel through the tank as part of the flow path. If the system gets warm enough then as the coolant expands it may push some up into the tank

Ok so as the car gets warm, like on a hot day, the air expands into the tank forcing the coolant down in its place into the cooling system. So that coolant being COLD is normal?

Thank you so much, peace of mind.

 

[DSG2003Mach1]

A properly burped system shouldn’t have any air in it (outside of the airspace at the top of the tank). At those temps, depending on what thermostat you’re running, it may have never even fully opened

It just gives the coolant somewhere to go when the fluid expands due to temp increasing as well you’ve got some extra should you have a leak.

The intercooler tank is part of the flow path so it’ll be warm

 

[X3FBrian]

A properly burped system shouldn’t have any air in it (outside of the airspace at the top of the tank). At those temps, depending on what thermostat you’re running, it may have never even fully opened

It just gives the coolant somewhere to go when the fluid expands due to temp increasing as well you’ve got some extra should you have a leak.

The intercooler tank is part of the flow path so it’ll be warm

My intercooler fluid is cold too, to the blower, but I have a big tank, high flow pump, and some fans that are on full blast all the time. My IAT's were 60* on the way home, 70 mph in 50* outside temps help hold that temp.

I recently did all these cooling changes a few months back so sometimes I'll check all the fluids and noticed the expansion tank coolant is just cold lately. A month ago, that fluid would be hot but I would see 190-200 temps.

Thanks for the reassurance however. Cold coolant in the expansion tank on a cold night must be normal.