So it started squealing again, even worse than before. It was the fan clutch. Makes sense with the symptoms, though: chirped on startup but got loud as ambient temp increased. Fan spun freely no matter how hot it got (clutch is supposed to lock when hot at idle to fully engage fan). Squeal was constant and did not match engine RPM.

Notes on replacing the clutch:
- Remove shroud and fan assy together.
- Remove 4 bolts holding assy to pulley with flat, ratchet head 1/2" box end wrench (space is tight so once you get the wrench on the nut you can just ratchet the nuts off).
- Worked best for me to remove nut facing right looking down, then rotate pulley 1/4 turn to access the next one.

I bought a Torqueflo unit at Autozone and it is about 1/4" thicker (closer to the radiator), so its a challenge to slide it in place without folding over radiator fins.

Hope this helps someone...

Paul