Wow. I wonder if it overheated sometime in its past.

I'm not even close to an expert on the 4.7, but I currently have two trucks with it.

My 4Runner has 134.5k and Tundra has 226.4k. Two weeks ago I towed a 17' enclosed snowmobile trailer (loaded) 4 hours each way with the Tundra.

Only thing I've done other than regular maintenance is exhaust manifolds. I've never even had to deal with the air pump failure.

Only cooling system issue I remember on any of my Toyotas (Lexus) I can think of was on my old 2000 LX470...the thermostat housing would leak no matter what I tried.

Forgive me...I don't know California/Nevada at all..is it cold at night where you are? I get milky stuff under the oil caps on our vehicles when we drive them a lot for short distances in the winter. Did you see any sign of it on the dipstick?