Ok, thought I had this figured out, but seems I was mistaken.....

In the picture are the two different sensors, the one on the top is the early style and the one on the bottom is the late. These sensors thread into the engine block behind the other water temp sensor that actually sticks into the water flow.

I am not sure what these sensors report to, maybe the DME or the idiot light - I don't know. What I do know is that the late harness in my car needs to see two terminals of some sort and the early sensor only provides one. The late sensor will NOT screw into the place of the early one - pretty obvious if you look at the picture.

I need to know what to do with the wiring harness - if I need to splice something in, fine - if I need to make a little intermediate harness to interface the early sensor, that's fine too - just at a loss as to what to do here.......

 

Just a guess, but maybe the early car uses the engine block as a ground in place of the "second wire" in the late car. Perhaps a comparison of the electrical diagrams would reveal the answer.

 

Thanks guys, finally figured it out last night - sensor in question sends a signal to the instrument panel and the early/late sensor operate in a completely different manner. Solution is to drill/tap the correct hole for the late sensor, not a problem - I am a machinist and the engine is on a stand......thanks again everyone for the info!

 

That's not what I wanted to hear. What early year is this motor?

I will be getting my parts back from the machine shop later in the week. It's an 86 motor going into an 87. No belt auto-tensioner, but will the temp sensor be different? Unlike you, I am not a machinist

 

You may be lucky and have one with the correct hole already, Legoland951 had a situation like this. My early engine is from an 84 car, so it's certainly an EARLY engine.

Another option is to drill/tap the coolant bleeder hole for the sensor and mounting it there. Nothing can go irreversably wrong here, at worst you have to find someone parting a car and buy a new water fitting.

 

MAn I can't believe this.

I had to swap mine and it was as easy as pulling form the 86 parts car and installing on the 83. When I get to the shop tonight I'm going to take a closer look and see if there is another tapped hole ...perplexed

 

86 engine is late, explains alot!

 

I am going through this as well. If you measure resistance on both, one of the terminals on the late unit is close to the early, so I am planning to try it by just hooking up the one wire to the late sensor. If needed I will mentally recalibrate the gauge reading. I looked at resistances both cool and hot. I'm assuming the second terminal on the late is for better grounding, but I don't recall what the wiring diagram said.

Smaller sensor would be a pain to get into the water stream, a semi-clever adapter would need to be made. Not impossible, but I figured my plan was worth a shot before cranking up the lathe.