Having a cooling issure that has me stumped and looking for the right fix.

First off....
'89 trans Am, 305, Auto, TPI, no mods, all stock, 195 thermostat.

The car sat up for approx a year and I started it up today. Drove it easy for a 10 or 15 minutes to get all the fluids moving again. Temp went to 210'ish on the guage (normal for my car). When I got back, popped the hood and saw coolant spraying out of the upper hose connections.

The upper hose was hot and hard as a rock.

Let it cool off (the pressure went away). Figured the thermostat was stuck so I took it out, sealed everything back up and started it up. With the radiator cap off, I could clearly see good flow in the radiator so I know my water pump is fine. Went for another drive with the thermostat out, another 15 minutes or so. Temp stayed at 180'ish while moving so I know I have decent flow and the radiator is cooling.

Turned the heater on to get flow through the heater core, and got the old steamy coolant blowing out my vents (Turned the heater off).

Got home, opened the hood and had the same condition...Hose hard and coolant spraying out of the upper connections.

I doubt I have a head gasket problem because the oil and coolant is clean and the pressure builds along with the heat in the engine.

What could my problem be?

Radiator cap? Bad thermostat?

Any suggestione greatly appreciated.

Bad cap

Replaced the thermostat just for grins.

Tried the cap....same issue. Beginning to think its just the upper radiator hose.

I would've replaced the hose in the first place, rubber tends to not work properly after sitting for a period of time out of use.

I'll do that Dakota...

Correct me if I'm wrong....
OEM calls for a 15# cap, Oriellies looked it up and it came back as a 16#...went ahead and bought that one. It's leaking at the top rad connection...the hose that goes from the rad to the thermostat housing.
If I have more than 16# of pressure, my cap should vent right?

The Oreilly caps is HORRIBLE, ask me how I know, go get one from Napa.

Yes

Not enough difference between a 15 and 16 psi cap to worry about.

Thats what I figured.Im gonne replace the rad hose...only a few bucks. And check the line to the overflow tank....We have millions of dirt daubers around here...never know. lol

Leak confirmed. Finally got some free time to fiddle with my cooling again.
Replaced the upper hose...still leaks at 210-220ish.

Figured I start it up and let it idle up in the driveway to see what is actually happening.
Had a handheld thermometer...and, of course, new thermostat and upper hose already replaced.

Let it idle to heat up completely....

-At 195'ish, the thermostat began more flow (195 thermostat working fine)
-At 220'ish, fan kicks on and the temp quickly drops to 195 then turns back off (ECM/Fan parameters and Fan relay working as expected)

Somewhere around 200-210, I see coolant bubbling out about 1 inch below the upper hose connection. Doesn't appear to be leaking in the plastic. The leak seems to be coming from the soldered areas. Actually surprised, I would expect the 23 year old plastic to fail before the solder.

The 16# radiator cap still hasn't vented to the overflow yet...at least not that I can tell. The leak is sufficiant enough that the pressure never reaches 16#...go figure!

I did note that, while idling, the temp stayed exactly between 195 and 220. When Im driving, the temps will rise to well above 220, even into the 240's, causing the leak to be more dramatic. Air dam perhaps? The cowling onder the engine bay is missing a few of the plastic connectors and droops, the air dam is in place and in good shape, it's just not positioned where it was long long ago.

Getting a new radiator tomorrow...thinking I may need to slide under the car and see if I can reposition the cowling/air dam to get things back where their supposed to be.

Any updates on this? Were you able to correct the cowling/air dam with no trouble?