213 is getting fairly warm if reading from the ECU as that sensor is positioned in the block close to where the coolant first flows after being cooled by the radiator.
I have been seeing the same thing. I have my stand alone innovate temp guage in the upper water neck. I tapped my original pipe and installed the sensor while the pipe was out of the truck to ensure the tip of the sensor is dead smack in the middle of the coolant flow. Once up to operating temp, my ultraguage shows about 12-15 degrees cooler than my stand-alone in the upper pipe. Driving around today in 94 degree temps, ECU was seeing 190, upper water pipe was showing 203.
I found the coolant flow diagrams, and to me it looks like the coolant first flows through the block around the cylinder walls (where the 3 temp sensors) are and then works up into the head, heater lines and throttle body before finally flowing back out the upper pipe to the radiator. I would expect to see some temp differences between these two locations based on the flow paths.
My thinking is that toyota designed the upper temp limits (AC cut-off at 226) based on temps in the block, not temps in the head. So as long as the ECU temps from the block are behaving nicely then +15 at the upper pipe should be fine.
I spent a considerable amount of time trying to find others that have compared temps in these two locations and I could only find
@Photoman and
@turbocruiser discussing in a thread back in 2003. The difference in temps seen back then were only a few degrees, much less than what we are seeing (up to 15 degree swing). I am thinking that running forced induction is contributing to those higher temp differences. I am going down the A2W intercooler path to drop IAT's and also building an external oil cooler. Time will tell, but I am thinking these two paths will help drop overall temps a bit more.
