Auxiliary water temp probe/sender on a 12H-T finally fitted. (1 Viewer)

[relaxedcruiser]

Hi guys and gals

For a while I was looking for a position to fit my auxiliary water temp sender/sensor unit on the 12h-t.
The stock one seems not to be very agile and always stays at the first marking. I was suspecting the engine would run rather cold but had a new thermostat two years ago and it didn't changed the position at all. But now I wanted a number I wanted to know how hot or cold the engine is really running. Bought a mechanical temp gauge mainly because I kind of liked the simplicity of that system - and the fact that the 24V electrical temp gauges were not ready available online that night.
But where the hell put that sender ?
Tried searching here and elsewhere but found only the same questions, not the answer I was hoping for.
First I had it in the oil cooler / heat exchanger housing at the position of the idle up vakuum switch. The readings there are really cool....the water seems to be right out of the radiator here (60°C) I felt a bit sorry for my motor to actually never get nice and warm...
Then I had the sensor in the top radiator hose but didn't like the fact that this position would read after the thermostat (70°C)
I wanted it in the same position as the stock sender but don't loose that stock sender/gauge to compare the instruments.
So today I had annother sharp look and found the position. I'm sure that that has been done before it's so obvious...so here are the pics ...
One deep breath and just do it I thought - knowing that I do not have a spare housing available.

I was lucky being able to drill the housing attached to the engine, and this made sure too that I would get the right angle for the probe to fit perfectly between the brackets. Ran a vakuum cleaner on the other side during drilling/tapping to pick up the shavings.
Drilled a 9mm hole

The socket in the housing acts as a dummy for the lower valve of the thermostat which closes the bypass circuit.

Tapped 1/8 NPT
It went all quite straight forward...

Job done !

Quite pleased with the result I went on a test drive - that revealed that my thermostat is actually opening to early - the water temp was sitting again at only 70°C like in the top radiator hose but I fitted annother thermostat so can´t really compare the readings. As all the readings were to low I am happy to order a new thermostat tomorrow. The temp options acording to the WSM and aftermarket supplier (Tridon) are 82 or 88 (89)°C.
The Gauge is reading true, before fitting I compared (and calibrated) it to the very acurate Auber 1813 which I use for the EGT together with boiling water - the definition of 100°C
I had this on my list for quite a while - and it took me just an hour in the end to get it done.
I hope that this will help some of you facing the same problem.

 

[coldtaco]

I’ve been wondering if one could use this guy for a aux water temp gauge, the yellow circled one. But I already was using the upper radiator hose for my aux gauge.

 

[relaxedcruiser]

You can use it - but the readings are way lower than at the thermostat housing. I used the vakuum switch port to the right as it is bigger and so I was able to fit the 1/8 NPT temp sender with an adapter. Bought a new thermostat today - interestingly the original Toyota one was way cheaper than the aftermarket ones available.

 

[David*BJ70]

I make it way more simple and less risky.

 

[relaxedcruiser]

David*BJ70,
I've seen your approach and I liked the hands on plumbery job when I was searching for a solution.
I wanted a more stock like result, location and appearance - wise, and I wanted it to function properly with the heater valve closed.
Of course you can mess up your thermostat housing. But If you feel capable to drill a straight hole where you want it to be - there is actually no risc involved.