I recently replaced the radiator and hoses on my 1997 Honda Civic and I started the bleeding process today. I let the car idle with the heater on full blast for about 40 minutes and I waited for the fan to kick on but it never did. 30 minutes in, the radiator started steaming a lot and coolant started to bubble out the radiator, but the temp gauge never read the car as overheating so im confused on what the issue is. Any help? Sorry if this is a newbie question

 

the fan sensor could be bad and needs replacing. Did you even replaced the thermostat?? It may be stuck closed.

 

Coolant boils at a temperature that is LOWER than water only... this would be a temperature below 212'F and thus, would not make the gauge needle move at all before the bubbling starts. This is why using a bleeder bucket is necessary because you have the room for lots of bubbles without making a huge mess while also allowing air to bleed out. The thermostat may be a problem, but you need more time to diagnose this.

 

Those are awfully big bubbles. I would be concerned about a blown head gasket. Did it bubble like that while the car was warming up?
As far as the fan turning on, it wont turn on until the car gets HOT. Depending on the weather, that could be 15 minutes or up to an hour.. Look up the proper procedure to bleed the radiator/heater core and try again..
Also, you had the heater on full blast. The D series engine actually runs very cool, the fan blowing over the heater core would be enough to cool the engine if it is not under load. Put the heater on max, but do not turn on the fan
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