I'm looking at putting in a 'real' coolant temperature gauge to go with an E-fan conversion. I'm wondering how different the original ECT and an Autometer temp sender are in terms of signal output. I like the idea of the Autometer gauge reading block temperature instead of reading the temperature of the coolant going to the radiator so that it could potentially alert of a stuck thermostat.

And barring another easy-to-tap location on the front cover, I was thinking about the factory ECT bung. The ECT itself is relatively new, so if the Mazda ECT and the Autometer sender have a similar enough voltage value, I'd just splice into the wires at the ECU and forgo another sensor under the hood.

 

the specs for the factory unit are in the FSM (www.foxed.ca) good luck finding the autometer ones!

actually i do have a plan B for you though. there is a 90's protege (later 90's like 97-98) that used a 3 wire ECT, it has the normal 2 pins for the ECU, and then a 3rd for the stock gauge in the dash, which would free up the spot under the oil filter for the autometer sender

 

That...is brilliant! The only question is if the Protege and RX7 ECT have the same signal output.

 

Is there any reason why I cannot tap a new hole for the Auto Meter temp sender into the water pump housing? I'm adding a Taurus alternator and there should be a good 3/4"+ of room between the top surface of the pump housing and the bottom of the alternator. This would be at the driver's side of the pump housing. Originally I thought it could be done up where the ECT is, but then I remembered the alternator goes there...

 

Is the passage you'd be drilling into deep enough for the sensor?
I don't know, just asking.

 

I'll have to check tomorrow. Not thrilled about sourcing a new gasket for the pump tho. No chance I can just use RTV for it, right?

 

I have the housing off and there is plenty of internal clearance. I'm a little nervous about drilling into it though. Will the metallurgy support a 1/8 npt fitting there? The wall looks a little thin to mount something into, esp. for cast aluminum.

And would putting the sensor in there need [good] teflon tape, or would sealing compound be better?

I've circled in red the planned location of the water temp sensor for the new gauge. This is not my engine bay nor my photo.

 

Damn, cannot edit the above post. :/

Well, it turns out I don't need to drill a new bore. The engine in my car is not the original engine, and I have always wondered what the sensor was just under my ECT. Well when removing the housing I broke the connector to that sensor and I looked it up. "thermoswitch - (AT/Turbo)"



So now I know that this engine was out of a 'Vert. Anyway, I removed the old sensor and now just need an adapter into the bore. Does anyone know the threading on the thermoswitch?