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Temp sensor mounting question.

CherryK5

CherryK5

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Right now I have my fan switch mounted in my thermostat housing. But vie noticed that my temp will hit ~200 before my fans kick on. Would it be better to mount it in my water pump or would that be worse? I think the main problem is that when the thermostat is opening up the water is just trickling through and not hitting the temp sensor. I dunno. All you electric fan guys must know whats up.
 
Best place for the sensor would be in the intake manifold water crossover BEFORE the thermostat. This might mean having to drill and tap a hole.
 
4X4HIGH said:
Best place for the sensor would be in the intake manifold water crossover BEFORE the thermostat. This might mean having to drill and tap a hole.
Click to expand...

Sounds dangerous. i'll check it out and see if i can find a good spot
 
my electric fan controller calls for it to be placed in the radiator, downstream of the fan. Granted, this is just a probe however, not a direct-to-water sensor. But I would think what 4x4high says is right, you don't want the T-stat affecting the sensor.

and 200* isn't bad, it's supposed to get to 195* anyway. Is it adjustable or straight forward xxx*- xxx* controller?
 
K85 Octane said:
my electric fan controller calls for it to be placed in the radiator, downstream of the fan. Granted, this is just a probe however, not a direct-to-water sensor. But I would think what 4x4high says is right, you don't want the T-stat affecting the sensor.

and 200* isn't bad, it's supposed to get to 195* anyway. Is it adjustable or straight forward xxx*- xxx* controller?
Click to expand...


Tstat and switch are both 180.
 
I actually tested several different types of thermostats cause I was having some issues with one.

Used a pot of water and a candy thermometer.

I found that even if I got 3 of the same thermostats (stant brand) that the opening temp varied as much as 15*.

That could be your issue, its possible the thermostat isn't opening till later than you think.
 
You are comparing the temp of the water in the block to the radiator which are going to be different until the engine is fully warmed up, and even then the block will be hotter because that is the source of the heat! :)

The reading at the thermostat housing will be different that the reading on the head - which is where I am assuming your "temp" is being read from when you say 200 degrees - if the thermostat housing has the fan temp sensor on the top of the inlet pipe. If the thermostat is closed the water is only circulating in the block and no water is flowing to the radiator anyway, so there is no point in having the fans kick on.

The temp that the thermostat opens at is not the temp your engine is going to run at either. It only OPENS at 180, but the coolant will always be hotter. Any thermostat is also going to have some hysteresis - that is to say that it will start opening at about 175 degrees (or so) and be fully open at 185 degrees (or so) so in the meanwhile it won't be fully flowing coolant.

Bottom line, it sounds like the design you have right now is exactly the way it should be. If you are overheating, that would be a problem, but you would probably see temps around 260 degrees or more to have that problem.
 
I just picked up my switch, a cole hersee, can't remember the p/n, but it has a 10 degree of variants either way, meaning that it's a 200 degree switch, but it can open at 190 or up to 210. Food for thought! Couple that with the late opening t-stat, that right there could be your problem. The best way that I can come up with a perfect way to turn the fan on is an adjustable control, that way you can 'dial in' the perfect temp to turn it on at!
 
What year is this truck? If it's TBI you should go to a 195 thermostat anyway. You will get more power and better MPG.
 
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