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66 Inline 6 (AC/PS/Auto)
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Discussion Starter · #1 ·
I have not done any test to see what my actual temp is.
This is where my gauge sits while driving after full warm up. Coolant is at proper level. Is this normal?
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The gauge is actually adjustable, but it should be noted that modern sending units on the engine are highly regarded as junk. But, sure, if the engine is running well in hot temps and not dumping coolant from the overflow, enjoy.
 
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I cannot answer your question, but after owning 2 66 Mustangs, I have never seen my engines at normal operating temperature, be that low on the needle gauge. On my 2nd 66 Mustang, it started out as an I6 and the needle would sit a little left of center, but not that far left. I installed a 289 with a new sending unit and it sat right in the center of the gauge. As a test, I took the sending unit off my 200 I6 and installed it on my rebuilt 289, and it sits like it did with the I6 in the car, just a little left of center. Since this was normal for me, I left the old sending unit from my I6 in my rebuilt 289. In addition, I did get a 25 dollar actual gauge, temporally installed it, drove around with the gauge taped to my wiper, to know how the car reacted in different driving conditions, so I would know what my needle indications would be. For me 180 degrees maybe up to 190, is just a little bit left of center and my normal operating temp running down the road. I suggest getting an actual gauge to know what you really have and m maybe a new sending unit. What temp thermostat do you have?
 

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Mine is the same. When I had the V8 in it the gauge would be a little over half-way to "H" but the 6 consistently runs where yours is. The sender I used is the one that came with the engine, maybe not a 73 but certainly not new.
 

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Mine usually sits a little higher than that once it's warmed up but not too far. If it gets to 1/2 way I start to worry.

This is the normal spot for my 200 once it's fully warmed up:
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OP, that's about where mine sits.
It goes a little higher before the thermostat opens, but then it settles down.
 

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Another data point for the OP - my '66 200, original engine, sender, and gauge, usually runs with the needle between the "T" and the "E" on the gauge. Not that I expected it to, but that didn't change with a new radiator and water pump.
 

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Mine usually sits a little higher than that once it's warmed up but not too far. If it gets to 1/2 way I start to worry.

This is the normal spot for my 200 once it's fully warmed up:
View attachment 813427
^^^ That's around where mine sits too most of the time once the engine has warmed up and in normal driving. The most I have seen the needle move is in the middle (between C and H) which doesn't concern me. I did purchase a mechanical temp gauge to install temporarily so I can correlate the needle position to specific temperatures. This way you know what the actual temp is to needle position on the factory gauge. I haven't installed the mechanical gauge yet but will this weekend and I'll post my results in a new thread.

Oh, I have a 195 degree thermostat installed in my 289.
 

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That’s where mine sits with a 195 degree thermostat and three row radiator.
 

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Discussion Starter · #10 ·
I cannot answer your question, but after owning 2 66 Mustangs, I have never seen my engines at normal operating temperature, be that low on the needle gauge. On my 2nd 66 Mustang, it started out as an I6 and the needle would sit a little left of center, but not that far left. I installed a 289 with a new sending unit and it sat right in the center of the gauge. As a test, I took the sending unit off my 200 I6 and installed it on my rebuilt 289, and it sits like it did with the I6 in the car, just a little left of center. Since this was normal for me, I left the old sending unit from my I6 in my rebuilt 289. In addition, I did get a 25 dollar actual gauge, temporally installed it, drove around with the gauge taped to my wiper, to know how the car reacted in different driving conditions, so I would know what my needle indications would be. For me 180 degrees maybe up to 190, is just a little bit left of center and my normal operating temp running down the road. I suggest getting an actual gauge to know what you really have and m maybe a new sending unit. What temp thermostat do you have?
Unknown. Had the car 13 months. Had to replace the oil pan, battery cables, fuel pump, trans pan gasket and rebuild the carb before I could even enjoy it, along with getting rid of the points..
 

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The stock guages can be all over the place. But based on what I've seen on this site, most people's needle stay around the T and the E. That's where mine goes as well.

That said you really should verify what your actual warm operating temp is. Easiest way to do it is get a meat thermometer and put in the radiator cold. Start the engine and let it get up to operating temp.
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It's a multi-step process. First, determine the actual coolant temperature. If you warm it up with the radiator cap off and a bulb thermometer stuck in it (if you use SWMBO's candy thermometer make sure you don't tell her and wash it thoroughly) and it should be at around 200* when the thermostat opens. If not, replace the thermostat.

Next step is to check the sender resistance at that 200* temp... I'm not home so I don't have access to my chart, but something in the back of my brain says 26 ohms. That should put the gauge needle at dead center. If the sender is not close to that value then consider replacing.

Step 3 is calibrating the gauge which will require applying resistance to the gauge via the sender lead and setting the low and high limits through holes in the back of the gauge (there are small toothed wheels). Set the needle to the low line of the scale at 50 ohms and the high line to 16 ohms.
 

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Listen to @Woodchuck - It doesn't matter what anyone else's car's needle does, you aren't driving theirs. You need to match up your coolant temp to your ohms, the see where your needle swings at that resistance.

If you change out your IVR, sending unit, gauge, or even your wiring, you may get a different reading at the needle. The only way to trust your gauge is to match it to actual temp.

It's not worth anything to you, but with my current combination of parts, my needle points to P when at 205. This means a lot to me, and only me.

Good luck to you. Take the time to untangle your condition and you'll be rewarded with newfound trust in your gauge.
 

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Discussion Starter · #14 ·
Thanks for the info. I have my work cut out for me, after I drain fluid from the trans.
 

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While we're on the subject, I just made an interesting observation about my temperature gauge today.

I've had the cluster apart cleaning it up, adding new lights, etc. Apparently I must've hit the temp gauge too hard with the air hose, or the Q-tip or something because now that I've got it all back together it looks like it's jumped a tooth and is now running a bit to the left of where it's always run. It still moves about the same distance, but now instead of being a quarter of the way across the normal range, it's in between the two lines at the cold end of normal.

Here's the before and after starting positions:
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It's amazing how much difference the same gauge can have with the same temperature ranges just because it was bumped or set differently.

Just figured I'd share since we had this thread going and it just happened to me today now that I've got everything back together.
 

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I'm not sure @Magnus , but maybe your cleaning efforts knocked loose some debris that was keeping the needle from coming to full rest?
 

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Could be. I haven't had the dash apart in forever so I got used to where it was sitting whether that was where it was supposed to be or not.

It still works the same, I've just got to get used to the new position now.
 

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Checking the application info online for a replacement temp sender, I found that the inline 6's and V-8's use the same sender. I assume that the readings at the gauge would be the same between the two. With that said, my '66 V-8 car reads like this....
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I have never seen it climb to the A,B or C marks!
 

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Discussion Starter · #19 ·
Tested it last night at the cap, only got to 165. Guess what Im doing this weekend:ROFLMAO:
 

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Discussion Starter · #20 ·
While we're on the subject, I just made an interesting observation about my temperature gauge today.

I've had the cluster apart cleaning it up, adding new lights, etc. Apparently I must've hit the temp gauge too hard with the air hose, or the Q-tip or something because now that I've got it all back together it looks like it's jumped a tooth and is now running a bit to the left of where it's always run. It still moves about the same distance, but now instead of being a quarter of the way across the normal range, it's in between the two lines at the cold end of normal.

Here's the before and after starting positions:
View attachment 813647

It's amazing how much difference the same gauge can have with the same temperature ranges just because it was bumped or set differently.

Just figured I'd share since we had this thread going and it just happened to me today now that I've got everything back together.
What lights did you go with?
 
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