Coolant flow question

[zukatude]

As part of my HG replacement, I am also installing a thermocouple to measure coolant temperature more accurately than the worthless stock gauge. I read that some are tapping into the coolant tube off the drivers side of the cylinder head (that routes into the top of the radiator).

How certain is the collective that this coolant tube is the hot side of the head, i.e. coolant is flowing out this tube and into the top of the radiator? I'm not so sure because the t-stat is on the other side and I always thought the t-stat was on the hot side.

Can anybody verify which direction the coolant flows in the engine?

TIA,
Paul in Windsor, CO

 

[RavenTai]

Why don’t you just do the mod to the stock gauge? it is cleaner install than using an aftermarket gauge IMO,

https://forum.ih8mud.com/showthread.php?t=64252

Yes that is the outlet, modern Toyota engines have a different thermostat setup than you may be used to with other vehicles,

in most vehicles the thermostat closes completely stopping the flow of coolant until it gets hot, in this Toyota setup the water pump instead re-circulates coolant through the block and head until it reaches the opening temperature, then it will start mixing in cool coolant from the radiator into this recirculation, the thermostat adjusts the ratio of fresh and re-circulated coolant based on the coolant temperature,

If you look on the passenger side of the head there is a large pipe coming out and down to the water pump/thermostat housing area, that is the recirc outlet and this is where the thermostat is sensing temperature, on the drivers side of the head is the outer circuit outlet that includes the radiator.