When I installed my new 383, I forgot to remove my temperature sensor from the old engine before getting rid of it. On top of that, the car wiring harness (not the ECM one, the one that controls lights & gauges) was hacked up by previous owners.

I purchased the following sensor, which I have installed in the driver's side cylinder head:

Temperature Sensor

I found a broken wire that was the right color, so I hooked up my sensor to that. However, the gauge is acting oddly and I'm not sure why.

The gauge starts off at the bottom, but when you crank it, it immediately shoots up over the maximum. Once started, it drops back down to where you think it should...but then it climbs much, much too quickly. Within a couple of minutes, it goes up to 220, then all the way to the maximum shortly after. Meanwhile, I have a scanner hooked up and it's reading the temperature in the intake at 150 or so. Eventually, the temperature gets up to 180 (on the scanner), the cooling fan kicks on and the temp drops back down but the gauge just stays maxed out.

I'm quite confused by this because I would think if I had it hooked to the wrong wire, it wouldn't work at all. Since it works, just not correctly, I'm wondering if the sensor I bought isn't correct? Not sure if different temperature sensors send different signals or something?

 

Possibly the sender unit is faulty?

 

It seems, from the NAPA webpage, that this is not the right sensor. Their application chart shows only the 1970's Camaros.
So this might be a sensor that has a different scale from what you need.

O'Reilly lists a coolant temperature sender part # WT359 for $16.

 

Ah. Good catch. I had a hard time looking up a sensor because the motor I put in isn't stock and I don't know what it's out of - and the heads are aftermarket ones (Edelbrock Performer RPM). I couldn't find a sensor that fit, the threads in the head are much larger than most of the temperature sensors I found.

 

You can always use a thread adapter, these are usually NPT and you can find adapters at Home Depot or Lowes. Do not use plastic, though, you need a good ground in the threads so use a metal adapter. And no sealant tape either.

Hope this helps.
Lou

 

The sensor I have installed right now, I know I used a thread sealant - could that be my problem now?

Also, the first sensor I tried didn't fit and I actually purchased a brass adapter but I thought that was a bad idea - I figured you would want the sensor part (the part that contacts the coolant) to be in the flow of coolant to get an accurate temperature. Using an adapter moved the sensor out of the flow, I thought it might not be as accurate.

Is brass okay to use for this?

 

If the thread sealant was preventing contact, you would get no temperature reading at all (gauge pegged low - cold).

An adapter does move the sensor slightly out of the flow but not far enough to make it read differently so you do not need to worry about that.

Yup, brass is perfectly ok. Actually preferred (it does not corrode).

 

Thanks! Seems like another thing I should be able to know out in short order (I hope).

I appreciate the responses.

 

Engine sensors required are always related to the car ( gauges ) the engine is being installed in ;not anything to do with the engine type or vintage

 

Yeah, that makes a lot of sense...I'd keep myself out of trouble if I just thought about these things a little more.

New sensor is ordered and will be installed today. Thanks for all the replies.

 

I have another question relating to my gauge...

Now that the car is running, I can watch the temperature gauge. Seems to be working correctly, too. Goes up & is steady, drops when the fan kicks on, goes back up when it shuts off, etc.

My question is based on the temperature reading. When I have a scanner hooked up to the car, I can see that the fan kicks on at 180 and kicks back off at 170; the temperature never gets much higher than 180 while idling. However, the gauge is usually reading around 210 - 220. I know the gauge sending unit is in the head while the computer sending unit is in the intake, don't know if this explains the large temperature difference?

 

The gauges in our clusters are not precise to begin with. But a 30 or 40-degree difference sounds like a lot. It could be that your sensor in the head is getting old, it could be a little extra resistance either on its connector or its threads in the head.

The question is what an infrared temperature gun would read. That would tell you whether the forward ECM sensor is lying or the dash gauge sensor in the head.

Was your ECM chip reprogrammed for the different fan switching temperatures? Just wondering because 180 and 170 is not stock.

 

The sensor is brand new, literally just put it in. Heads are new, too.

I have a whole new set of gauges that I plan on installing over the winter - maybe I'll wait until I get those installed and worry about it then.

Yes, the ECM has been reprogrammed.