Water temp sensor locations
 

I have an FC aluminum water pump housing on my 12a, and I normally use the stock temp sensor location for my gauge located on the back side of the water pump housing. I have also ran a sensor in the radiator in the past as well. I have been thinking about changing the location to the sensor located in the rear iron right below the oil pressure sending unit.

Is there any advantage or disadvantage to one location vs. the other? I would think that the sensor in the block would be the most beneficial temperature to moniter. thoughts?

I recently upgraded to an aluminum radiator from rotaryworks. My temp gaguge is installed behind the water pump and a second gauge through the heater hose below the oil filter. There is about 30-40 degrees difference during hot LA stop and go traffic. I guess install it whereever it is convenient for you. Otherwise, get a hose adapter, old school tstat cover with a bung or switch to 12-a water pump housing

30-40 degrees... thats huge!

Which location gives the higher temp?

(I also have an aluminum radiator. Not from rotary works though)

Of course the outlet or behind the water pump will be higher. Im also using a v6 fiero efan with manual switch.

I think i'll just go with the one in the rear iron. Since I care most about the temp of the motor rather than water in the radiator or hoses...

Which makes it much easier for me to finishing hiding and tucking the engine bay wires...

yeah, I hear you. I just got so used to having it behind the water pump, been doing it since the 80s per racing beat manual and conversation with several road racers. The only reason why I have two gauges was for second opinion as this is my first experience with aluminum radiator. In addition, I was worried since most of friends with aluminum radiator have lower temp with their thermocoupler mounted on the rear plate or heater outlet.

the thermostat measures the temp of the coolant leaving the engine, which should be the hottest part.

The hottest part should be in the rear plate somewhere, since the coolant flows down to the hottest parts of the engine first, then back up across the top/intake area actually heating those areas up.

I have the stock gauge/sender as well as a mechanical gauge threaded into where the throttle body water outlet on the rear housing of an EFI car is. My Megasquirt gets its temp information from the stock EFI temp sender. There's a bit of hysteresis between the three but they all generally read similar.

I wouldn't ever put a temp sender in the radiator or the heater hoses. The radiator doesn't see engine temp, and the heater hoses don't flow any coolant if the HVAC is turned cold. The temp control knob moves a coolant valve in addition to a blend door.

also have mine in back of the pump housing.

Mine is in the back of the water-pump housing, seems to be the most accessible spot.

I would think that the rear iron has the hottest location given it's so close to the the spark plug/combustion area of the motor...

This is where its going for now. If I notice something wrong I can always swap to the housing. It's a 5 minute job. I might just check back to back to see what differences i get and if there is any fluxuation between them.

Also, I do not run a thermostat in my motor. And I am running an electric water pump that moves the water at a constant speed vs. varying speeds while turned by the RPM of the motor. Just thought I would throw that in there...

Are you at least running a restrictor in the water outlet?

A restriction of some type is crucial. The water pump needs to be able to pressurize the cooling system.

I think he has a drag car?

Well, this is not for my drag car. Its for the 12a in my Rx2. I am not running a restictor or anything similar. The small passeges in the motor, thin passeges in the radiator, the water pump housing itself, ect. are all restrictive enough to keep everything doing its job.

I have ran every rotary i have ever owned like this for the past 10 years.

some blocks have a threaded bung low down on the front plate near the timing cover valley on the spark side
.. -at the very end of the coolant flow through the block before its fed back to the water pump/ thermostat assembly
NOTE - its a bigger fitting.. you can use adapter.. you can tap the original bung .. you can use the larger sender from same year piston engine

i have mine in there - FC block,, but the same plug is provided on many earlier engines
( on FC engines , adding a sensor to more the imited space at back of water pump is hard to get to )

if you delete the thermostat , you simply put a pipe bung in the bypass/ recirc port below the thermostat position
( as is done to MFR water pump housings )

Where can i get this reader? Mine is just plugged with a bolt. Thanks!

If you're careful, there's enough room to tap a 3/8" FNPT hole in the back of the FC aluminum water pump in addition to the hole for the OEM temp sensor. I use the 3/8" NPT hole to mount the temp switch for my electric fan and the OEM temp sensor to control the electric choke hold.

If you're not running a thermostat, are you running an electric water pump controller that varies flow based on engine temp?

What brand / flow rate electric water pump are you running?

Here is what I did on my FC (1986-1988) aluminum water pump housing on my 12A. It holds the factory sensor for the choke and an after market temp sensor. I also have the sold school neck and another sensor in it. This way I can measure both sides of the t-stat.

https://cimg4.ibsrv.net/gimg/www.rx7...596116cd06.jpg

https://cimg2.ibsrv.net/gimg/www.rx7...d40ff26ff4.jpg