You know that fitting on top of an aftermarket water pump that is used for the heater on older cars? Well would I be able to put an elbow in it and screw in a fan turn on switch? Is there a big difference between the temp of the water in the pump and the temp of the water in the stock fan switch location in the head? Wouldn't the switch see the hot water comming right out of the heads there or would it see the cooler water comming out of the radiator? I was thinking of just putting a plug into the head and rerouting the stock wire to that spot. Would it work and what is the thread pattern 3/8, 1/2 ..?
Thanks!!

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1989 Iroc-Z L98 Original engine-58K miles!!

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Putting it there would also eliminate heat soak from the headers too. Right?? My main concern is that it would see the coolant comming from the heads so as to get an accurate turn on temp.

 

That fitting unfortunately is on the cold (suction) side of the water pump, not the hot side, unless you have a reverse-flow system. So it wouldn't work very well for that purpose.

However, there may be extra holes up on the intake or water outlet somewhere, that you could use that way.

The fan swith is 3/8" pipe (a kind of bastard size) where most of the fittings on the motor are 1/2" pipe.

Personally I'm not sure which temperature is the one most indicative of cooling needs, water temp or casting temp. Obviously the one in the heads is affected by the casting temp as much as or more than the coolant temp. I would think that casting temp is the actual important thing that would actually be what you'd want to base your cooling system control on, not coolant temp; but in practice it's probably splitting hairs. Still, it might be worth some experimenting.

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"So many Mustangs, so little time..."

 

Since my fuelie heads have no provisions for temp sensors, I moved the temperature sensor that my gauge uses to the water pump. It was super easy because any hardware store will have a brass adapter that screws right into the hole and is the correct thread for the sensor. Problem is, my needle never goes above 110*.

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RB, you are right. The casting is what really matters, because it will warp beyond a certain temp range. That is why (I believe) GM moved the sensor from the old position (intake?) to the cast iron cylinder heads. Sure the coolant temp is important, but think, why do we have coolant in the engine. It is to cool the cylinder heads and block from the heat generated from the combustion chamber and process. We don't want to damage the rings and planar mating surfaces of the block and heads because of heat. So if you place the temp sensor on the water pump, you will see lower temps, but you will not see the actual temp at the cylinder heads (guess why they have cylinder temp gauges. ), which can be damaging. Keep it where it's at, there is a reason for it being there and it works.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

 

As RB83L69 says, the water pump is on the cool or radiator side, and is not indicative of the temp out of the engine. You didn't really say why you want to do this. But, if you want to relocate it, the best bet would be to get a thermostat housing with a port in it - I know these are available for carb-type intakes, but I can't say I've seen them for TPI intakes.

FWIW, my LG4 has a switch tee'd into the location you're indicating, but that is in the heater return line. The switch runs a fan that blows air onto the carb when the engine is off and heat soak could cause vapor lock when the engine is started again. For this use, though, there is no flow (at least not being pumped) past the switch.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, exhaust, paint, etc.).
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