My car recently is having overheating problems.

Car was driven on freeway when the temp needle started climbing. Before this the temp showed normal or sometimes very low.

I noticed during the overheating that the hot air is not coming out of the vents. But at times when the hot air does come out, the temp needle returns to normal. I can also hear a wirling/grinding sound from the dash in front of the driver when the hot air is turned on.

It seems like it's a clogged water hose? or some other device that's not working properly? Is it the mono-valve? Any insight is appreciated!

Car is a 1985 300d california edition. Thermostat changed a few months ago.