I have a bit of an odd question. . does anyone know if there's any GM-spec water-temperature sensors that will thread into the stock hole on the engine block.. without me tapping it?

I'm having trouble getting megasquirt to read the Mazda unit, I think my temp sensor might be screwed up anyway, so instead replacing the unit with a stock mazda sensor, and still modifying the MS unit, I figured it might be easier to just drop a GM sensor in.


Year/Make/Model of vehicle if known

Thanks!

~Wonko

 

Dont know what GM sensor fits but anything that is 1/8" NPT will fit in the stock sensor location.

 

Righto.. I guess that's what I needed Thanks!

 

There are two coolant temp sensors on the FC engine, one for the dash gauge (located under the oil filter in the rear iron), and the other for the ECU (backside of the water pump, under the alternator). Make sure you are wiring the ECU sensor to the MS, as the two sensors have different characteristic curves. These are very robust units, with a corresponding low failure rate, so check the rest of your system and hardware carefully first.

Also, the gauge sensor might be 1/8NPT, but the ecu sensor is a straight thread, not 1/8NPT.

 

Yea I was referring to the water temp sensor (on the block) and not the waterthermosensor on the back of the wp. I am positive the water temp sensor is 1/8" NPT because I have an aftermarket sensor that is 1/8" NPT and it fits there fine.

 

I just went to autozone, they had the correct one.

 

The "Mazda" water temp sensor is actually very common among imports. I recently installed a Megasquirt onto a Toyota Celica Supra, and it used the same sensor.

 

Is this true between s4 and s5 water temp sensors as well? I know the s4 and s5 gauges read differently but wasnt sure if it was the gauge itself or the sensor.

 

We're talking about two different sensors. The gauge sender is different between S4 and S5, and while I'm sure other cars use a similar sender, I've never seen one on any other car but the RX-7.

The ECU sender is located on the the back of the water pump housing, and it is common between a lot of cars.

 

I made the mistake of installing the MS to the one below the oil filter, since I didn't realize the other one was the one that was "normal"... I coudn't find a difference documented anywhere. And I already had a mechanical water guage to tap into the other one's location...

Good to know for the next 7 I install a MS on

Speed_Monkey - What car did you say it was for? I only have advanced around here and I can't go and ask for a 1/8 NPT water temp sensor, as they're useless without their computers.... which only list by year/make/model.

 

just for the record, the thread for the one on the block is NOT 1/8" NPT. I've included a pic for reference. the shiney one with the spade connector is a new GM spec 1/8" NPT threaded one, and the other is the on that was pulled out. I'm not sure exactly the size of the stock one, but the thread pitch is 0.75 (metric).

 

Very, very strange. I got a blitz temp gauge and blitz pressure gauge. The sensors are both threaded the same. The oil pressure gauge taps into my FC3S.org oil pedestal which is tapped for 1/8" NPT so the only logical assumption is that the thread for the water temp sensor on the block is 1/8" NPT as well. I cant explain it and sorry for any confusion I have caused. Is the s4 and s5 water temp sensor exactly the same thread/pitch? That's the only thing I can think of.

 

It could be a difference of S4/S5.. I dunno. I just got back from Advanced, and was looking through their book of sensors. The Mazda ones that my car has is a M8X.75.. There's only one sensor that uses that thread pitch (Mazda).. So I just kept ahold of this one, and I'll just tap a hole on my water pump housing, next to my mechanical gauge hole.. then I'll have three ways of monitor water temps: Laptop (through MegaSquirt), Mechanical Gauge, and Dash gauge. best of all worlds, I guess.

 

Mazda used several different senders. They used to use standard NPT thread roughly earlier then S5, and then switched to a metric straight thread. The issue is that you will sometimes come accross older ironds (S4) that use the metric thread as well. So it's fairly random. I may be reversing metric vs. NPT, but you get the idea.

 

That was nice of them... I like randomness in a car company.. keeps me on my toes

 

It's *not* 1/8"NPT-27.
It's actually 1/8"BSP-28.
The threads are actually very similar, and almost interchangable...almost!
If you don't match them up right, you will screw up the threads permanently.


-Ted

 

Good thing I'm just tapping my own hole.. I don't want to deal with potentially messing up ANY threads going into the block

 

Well, block is iron and the sensor is brass.
Guess which one is going to lose?


-Ted

 

Thanks for the correction Ted. For what it's worth I have a s5 t2 REMAN with new housings if that makes a difference. I used some teflon tape and had a somewhat difficult time getting the sensor correctly threaded but have removed it twice now and the threads are fine.

 

OK, BSP. I actually knew that, because I think it's on my website somewhere in "Ramdom Technical Facts".