Only because something didn't seem right, I just downloaded the manual for your Tundra.
If your grill thermometer is reading air jacket temperature correctly, and it's reaching something near 200°
before the blower kicks on, something ain't right. It should come on at 140°, shut off at 120°... and there is, or should be, a 160° limit switch that shuts down the air intake.
This is from page 60...
9.3 Fan control
The fan is activated when the air jacket temperature of the furnace reaches 140 °F and
stops when it drops below 120 °F. If the air jacket temperature exceeds 160 °F, the air inlet
damper closes and the fan will continues to blow until temperature returns below 120 °F at
which point the air inlet control will open again.
Although I did find a discrepancy... the wiring diagram on page 58 shows a 110° fan control and a 200° limit switch. Meaning the blower should start up when air jacket temps reach 110°, and the air intake should close at 200° (200° actually makes more sense than 160°... to me anyway). Either way, the blower should come on well before 180°-200°.