Fiero coolant leak & overheating

[noerrorsfound]

I was driving the Fiero and I gave it a good amount of gas while heading down the road, probably pushing it pretty hard but not more than I've done before.
I slow down and quite a few seconds go by. Suddenly, smoke is coming out of my vents, although the temp gauge reads normal. I find a safe place to stop.

I check the coolant overflow tank and it's a little low (at "add") but my heater core leaks into the passenger side so I have top it up occasionally. I had been noticing a loud noise coming from the vents when using my heater recently. Had been going on a while.

I hear liquid and look under the car and toward the front on the passenger side, coolant is pouring out.

So my brother leaves work and comes to check out the damage. The level of coolant hasn't dropped (I went ahead and topped it off) and the leak has stopped. We decide to bypass the heater core and we do so successfully with no leaks where we connected the two hoses. We let it idle a while, runs a little hotter than usual at almost 220. However, no leaks can be spotted under the car, either.

I drove the car cautiously and slowly (windows fogging due to vents and heater off) until I heard more coolant gush out. Turns out it just went into my passenger side. No leaks under the car.

We drive farther, a couple miles perhaps. I stop just as a precaution in a parking lot and we look under the car, although the temperature is still about 220. However, we see coolant pooled under the car. And drips. And pretty soon the radiator fan kicked on & the car was overheating.

So what's going on?! Help us figure this out. Three closeup pictures of the leaking area are attached to the post. Here's also a picture that shows the general area the leak is in under the car:

 

[Oreif]

First, there is a special way to fill the Fiero cooling system. If you get a leak and lose some coolant you cannot just top it off. You will end up with air pockets in the system which will cause a lot of issues.
The best thing to do is check the entire cooling system for leaks then properly fill the system.

Materials:

The Fiero cooling system requires nearly 4 gallons of coolant to fill, if the system is empty I highly recommend buying 4 gallons and keeping whatever is remaining to add as needed.

Important notes: There is apparently an error in Stant catalogs regarding the radiator cap. The correct Stant part #'s are 10230 or 11230. You want to ensure the cap is non-vented. You can identify a vented cap by the lack of a spring, the non-vented caps are spring loaded.

Process:

Filling:

Car was on level ground or nose down, engine completely cool overnight.
Remove both the rad cap and the thermostat housing cap. If you are just topping off the system, leave the radiator cap on.
Fill from the thermostat housing until coolant just reached the lip of the radiator filler, then capped the radiator. Approx 1 1/2 gallons of coolant.
Continue to fill the from the thermostat housing until coolant reached the heater line connection in the housing.
Fill the reservoir to the "Add" level.


Burping:
Close the thermostat housing, leaving the thermostat out.
Run the car for a short time, 15 seconds or so.
Wait a few seconds after stopping car, then open the thermostat housing again and fill back up to the heater line.
Repeat the process until opening the thermostat housing after running reveals the coolant has not dropped at all. For me, this was about five times. Reinstall the thermostat. Check the coolant reservoir and make sure it is full. Watch it closely, as any remaining air in the system should be purged from the system through the reservoir, make sure to keep the coolant above the "Add" level, so check it for the next few days and every so often after that.