Smoking/ steaming & bubbling out of reservoir?

I have a 1998 honda civic dx 1.6 4 cyl. After I drive longer than 15 minutes you can smell coolant/antifreeze and car starts to smoke, My temp gauge inside the car does not work so i don't know if it's overheating. I open the hood and a bunch of steam/smoke is coming out of the reservoir, so I open the reservoir cap and most the smoke is coming out of the hose connected to the reservoir cap. And it also seams to be leaking from reservoir or something near it, cause I'll put 50/50 in the reservoir and after 15 minutes it's empty. Help please i don't know what to do or buy to fix it.

The line would be underneath the reservoir am I right? And I've looked under there before and I can't tell where it's coming from because it's dripping.

Check your oil for coolant, then do a compression test but my best guess is that you blew your head gasket. If so, a 98 Civic probably is not worth the expensive HG repair, sorry.

Look for leaks in the line and check the thermostat.

What Jason said plus check heater core.

'Hi so the coolant system has a leak which is why it boils over as most cars working temperature is 122 degrees c due to being a pressurised system.
so that is why you are advised never to do what you did remove the radiator cap from the reservoir. As the steam would cause severe scalding.
so one important component which losses it's usefulness is the radiator cap. Over time it's spring becomes weak and this stops the engine reaching it's working temperature the least expensive item causes the most problems.