Coolant temp sensor locations

sen2two · 07-06-2012, 08:14 PM

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?

rxspeed7 · 07-06-2012, 10:31 PM

Your going to get more flow past it by the thermostat and give you more accurate readings there. In the rear iron your likely to get stagnant flow.

sen2two · 07-07-2012, 09:05 AM

Thats true. but I am leaning towards the rear iron location since I care more about the temperature of the motor more than water flowing through a system.

Pete_89T2 · 07-07-2012, 10:17 AM

I think the choice depends on what you are using the temp sensor for. Are you using it just to drive a gauge to monitor temps, or is it being used as a coolant temp input to a stand alone ECU?

FWIW, Mazda engineers chose the real iron location for the dash temp gauge, and the water pump housing for ECU control purposes. For the latter ECU case, you'll want to sense coolant temps as it exits the engine in a place that sees steady & uniform coolant flow and isn't as heat soaked by the thermal mass of the structure it bolts into, so the sensor can quickly respond to small changes in coolant temp due to engine load. The WP housing fits the bill nicely here.

For a guage, where you just need it to warn you of trends toward impending doom, the rear iron location works nicely because it's physically closer to the spark plugs where combustion happens (localized hot spot), so it will respond to a boilover trend before the WP housing location would. Also, the physical location in the rear housing would probably heat soak a bit more than the WP housing site, so your gauge would have less pronounced fluctuations vs. load. Ideally, once the engine is warmed up to operating temp, you won't want to see too much of rate of change in the temp gauge reading, but you would want it to rapidly respond to a boilover condition.

sen2two · 07-07-2012, 12:58 PM

Its just for a gauge... This motor is has webers, so no ECU.

I'm going with the Rear iron location.

sen2two · 07-07-2012, 01:00 PM

Its just for a gauge... This motor is has webers, so no ECU.

I'm going with the Rear iron location for now. It's only a 5 minute swap to another location.

07-06-2012, 08:14 PM	#1
sen2two KTEC Join Date: Jan 2009 iTrader: (2) Posts: 642 Rep Power: 0	Coolant 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? __________________ what I have: 1985 Gs:12a All motor Drag car - 1973 Rx2: Play car What I had: 93 Touring: TRADED - 91 Coupe: TRADED - 90 GTU: RHD - 88 10AE: SOLD - 87 Base: SOLD - 86 Base: SOLD - 1985 GSLSE - 85 Gsl: SOLD - 80 Gs: TRADED - 1972 Rx2

07-07-2012, 09:05 AM	#3
sen2two KTEC Join Date: Jan 2009 iTrader: (2) Posts: 642 Rep Power: 0	Thats true. but I am leaning towards the rear iron location since I care more about the temperature of the motor more than water flowing through a system. __________________ what I have: 1985 Gs:12a All motor Drag car - 1973 Rx2: Play car What I had: 93 Touring: TRADED - 91 Coupe: TRADED - 90 GTU: RHD - 88 10AE: SOLD - 87 Base: SOLD - 86 Base: SOLD - 1985 GSLSE - 85 Gsl: SOLD - 80 Gs: TRADED - 1972 Rx2

07-07-2012, 12:58 PM	#5
sen2two KTEC Join Date: Jan 2009 iTrader: (2) Posts: 642 Rep Power: 0	Its just for a gauge... This motor is has webers, so no ECU. I'm going with the Rear iron location. __________________ what I have: 1985 Gs:12a All motor Drag car - 1973 Rx2: Play car What I had: 93 Touring: TRADED - 91 Coupe: TRADED - 90 GTU: RHD - 88 10AE: SOLD - 87 Base: SOLD - 86 Base: SOLD - 1985 GSLSE - 85 Gsl: SOLD - 80 Gs: TRADED - 1972 Rx2

07-07-2012, 01:00 PM	#6
sen2two KTEC Join Date: Jan 2009 iTrader: (2) Posts: 642 Rep Power: 0	Its just for a gauge... This motor is has webers, so no ECU. I'm going with the Rear iron location for now. It's only a 5 minute swap to another location. __________________ what I have: 1985 Gs:12a All motor Drag car - 1973 Rx2: Play car What I had: 93 Touring: TRADED - 91 Coupe: TRADED - 90 GTU: RHD - 88 10AE: SOLD - 87 Base: SOLD - 86 Base: SOLD - 1985 GSLSE - 85 Gsl: SOLD - 80 Gs: TRADED - 1972 Rx2

07-07-2012, 10:17 AM	#4
Pete_89T2 Lifetime Rotorhead Join Date: Apr 2010 Location: Elkton, MD iTrader: (1) Posts: 874 Rep Power: 15	I think the choice depends on what you are using the temp sensor for. Are you using it just to drive a gauge to monitor temps, or is it being used as a coolant temp input to a stand alone ECU? FWIW, Mazda engineers chose the real iron location for the dash temp gauge, and the water pump housing for ECU control purposes. For the latter ECU case, you'll want to sense coolant temps as it exits the engine in a place that sees steady & uniform coolant flow and isn't as heat soaked by the thermal mass of the structure it bolts into, so the sensor can quickly respond to small changes in coolant temp due to engine load. The WP housing fits the bill nicely here. For a guage, where you just need it to warn you of trends toward impending doom, the rear iron location works nicely because it's physically closer to the spark plugs where combustion happens (localized hot spot), so it will respond to a boilover trend before the WP housing location would. Also, the physical location in the rear housing would probably heat soak a bit more than the WP housing site, so your gauge would have less pronounced fluctuations vs. load. Ideally, once the engine is warmed up to operating temp, you won't want to see too much of rate of change in the temp gauge reading, but you would want it to rapidly respond to a boilover condition.