last week my cooling system pressure tank sprung a leak so I quickly ordered a new stainless tank from Hall. I did not come with a place to screw in the sending unit. I installed it anyway, thinking that the sending unit on the radiator is regulating the dash gauge. It does not appear to do so. By fussing with the system, maybe I created another issue and that's the real culprit.  I'm to be in a parade tomorrow but fear the worst, driving slowly without a temperature gauge may be a bad idea.

Is the gauge on the radiator working in unison with the pressure tank gauge? Is there a quick fix or do I give up on the parade?

Original Post

Actually, the sender is best installed in the front of the block.

I have two gauges (a capillary gauge, and the stock electric).  My capillary gauge is installed in the block, but this is the location where the "guru's" tend to recommend the sender should be fitted.  There may be a pipe plug in yours now.

See the brass adapters between the heater outlet ports?



07-09-2014 [6) (Medium)a






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your motor looks amazingly clean, but it doesnt look like you are fully plumbed. Is that sending unit taking the place of the one on the expansion tank? I assume I can use the same sending unit that was on the tank. That may be my fix, but not by tomorrow. Where did you get the brass adaptor? 

Thank you.




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The sender from the tank should screw right into the block location once you remove the plug. As I recall from many years ago the existing wire is long enough to reach the new location. Should take less than an hour all in.


The picture was just for illustration.

All the hoses should be hooked up when you are done.



- plug the new tank (I guess by the way that you are missing the groud connection hence your device not working..)
- replace electrical sending device, fits in the opening as per picture from Rocky

- my obsevation due to the new position the temp change is more "dynamic". 


 The temperature senders installed in the radiator control the relays which in turn control the cooling fans. The temperature senders in the radiator have absolutely nothing to do with the water temperature gauge in the console. 

 The factory-installed temperature sender in the expansion tank is responsible for the console temperature gauge reading. 

Mounting the sender in the expansion tank was not correct and that is why most owners have relocated that sender to the engine block as outlined by Rocky.

 It was not correct because a hose failure or other coolant system leak would eventually cause the expansion tank’s sender to not be sensing the water temperature but instead the air in the now empty/low level expansion tank. 

 If your car has had no previous overheating issues then there is no reason why you should expect any just because you cannot read a current temperature. But it really is quite easy to correctly install the sender where it belongs.


Last edited by lf-tp2511

Rocky suggested to mount the sensor on the motor near the water pump where a pipe plug exists. This plug has been sealed since the car was new and does not want to budge. I've tried everything, but no movement. About two inches away is a similar plug, but located on the waterpump. The water pump is relatively new and this plug will turn. Is that a potential location for the sensor?

Larry, I thank you for your explanation. My car does run very cool since the big Fluidine aluminum radiator and sucker fans were installed, but I never drove in a parade for an hour or so at slower than walking speed. This made me nervous about going out there 'unprotected' without a working temperature gauge. All was not lost, I drove a friend's big block 65 Vette with side pipes. It's fairly loud too. 


Thank you for everybodies help.



 Mounting the sender in the water pump is an acceptable alternative. 👍👍

If you have an impact wrench of some sort they often prove successful in removing frozen fasteners where other tools fail. 

You drove a ....🤢🤢🥴🥴😱😱...... Corvette instead ❓❓

 Hope you took a shower afterwards. 😉


Now that was rude, coming from a nice, good advice giving Pantera owner. Well we all have our weak moment. To be honest, I also owned a new 69 Vette for 13 years, it was an outstanding tough car but the Pantera won out in the end. There were too many Vettes. I only wished that DeTomaso could have developed a rag top version. 


 Sorry my attempt at Ford versus Chevy humor didn’t come across well. 

 Maybe the often heard phrase  -

“ I’d rather push a Ford than drive a Chevy”

 would have been less objectionable ?



 I just flew in from Fresno, and boy are my arms tired. 

Badda bing, badda boom‼️

 I’ll be here all week.


Last edited by lf-tp2511

Hi Larry,

Actually I found your 'chevy' comment very funny, and absolutely no offense was taken.

Staying on the topic of the temperature gauge, my problem may have shifted. 

I installed a new sending unit at the water pump and ran the same wire to it, but I don't appear to be getting a signal to the gauge.

Yesterday I tested the gauge by sending current through the wire conecting it to the sending unit. It worked. So I hooked it all up in the same manner as it was before and ran the motor till hot. No movement of the gauge needle. Possibly it was not hot enough, but the expansion tank was too hot to touch, so I assume that the same heat existed at the sending unit. The sending unit came with teflon tape on the threads, but I can't imagine that there is no ground because of that. Even the water would be causing a connection. 


Any ideas what to try next?


Thank you,


 Did you stress that you wanted a sender  for a gauge and not for an idiot light? Even if you did, that doesn’t mean you got the right one.

 If you have removed, or can remove, the old sender from the tank I would suggest installing it into the water pump.  I assume the gauge was working with that sender, previously.

 That would either confirm you have an incorrect new sender or you have unearthed some other problem.




The old sending unit was working....however.... after I removed it from the old tank I ran a test. I wired it as it might have been if properly connected, and held it into the very hot water of the new tank with the ignition on, and got movement of the needle. I am stupefied, but will exchange the new for the old unit. 


Thanks again.



The senders are just temperature sensitive variable resistors. 

You can check "gross functionality" with just an Ohm meter. 

Here's some data from JFB, showing the relationship of resistance vs. temperature for a "typical" sender.  So if you have one at room Temp,, it ought to read AROUND 120 Ohms, and if you heat it up, you should see the resistance drop.

Anyway - a fun project if you have your sender, and are wondering if your sender is good or not...

You should also be able to plug a 25 Ohm resistor to the sender lead and ground, and your gauge should go to about ABOUT 200 Degrees.  Easy way to check the wiring and gauge.

(Plot credit Stephen of S&N Clocks)





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Last edited by rocky

My last statement should have said that I got 'no' movement of the needle. In the meantime I installed everything as it should be and hope to take test drive this weekend. That should tell me if indeed I have a problem that needs further investigation. Thanks again for your input.



Some sorry history on Pantera instrumentation: some 2 million Ford cars & light trucks used 351C engines with the water temp sender in the block. No one understands why Ford/DeTomaso added a temp sensor port in the expansion tank, except to purposely lower the gauge reading.

There are also two Ford/DeTomaso TSBs denoting two different low-wattage resistors to be spliced into the Pantera sensor wire- again, to deliberately lower the gauge reading. On my '72 L, the 'factory' resistor wasn't even soldered- only twisted into the cut sensor wire. So, sloppy connections came loose and the gauge stopped working. All this is because -A- the Italian Veglia gauge was supposed to somehow work with a mismatched U.S-made Ford temp sender.

And -B- the temp range displayed (0-220F) was too low in any case for the Pantera's normal working engine temp of about 200F. This nearly pegged the 0-220F gauge and panicked non-motorhead owners. This finally got fixed sometime in 1973 with a 0-260F gauge- which still may not read accurately but at least didn't peg the new gauge.

Bottom line: the typical 0-220F water temp gauge never did read true engine water temperature. If the car is not spitting coolant overboard, the engine is NOT overheating no matter what the dash gauge says. If you''d like, you can calibrate either gauge for good accuracy with a variable resistor tuned in that wire.

B- The Pantera sender is a 1-wire type. It is designed to ground thru the engine block. More than maybe 2 full turns of teflon plumbers tape seals coolant while electrically insulating some senders and you'll get no current to the gauge no mater what you do. ONE full wrap of teflon tape seals the low coolant pressure nicely & lets the sender ground normally. Some owners found the ungrounded sender but never made the connection about too much teflon tape. They fixed their cars by soldering a new ground wire to the sender body. Try grounding the inop' sender with a jumper; if it works, there's too much tape.

C- By NOT using TWO hex-nuts on the sender to retain the gauge wire, you run the risk of pulling the threaded stud (that makes electrical contact inside the sender), away from the internal sender element. What was supposed to happen was, a first nut is hand-threaded on the sender stud. Then the sender wire's ring-connector goes on and a second nut is installed. To tighten, the two nuts are torqued against each other, NOT against the plastic sender body. If your sender stud can be wiggled and seems loose, this is what happened.Needless to say, there will be no accuracy from a loose-stud sender no matter if the gauge needle moves. I've also found Panteras with inop' gauges; inspection showed the sender stud missing- pulled completely out of the sender body.

Your last problem is getting the 1/8-pipe plug out of the engine block. Ford practice at the time was to slam that little plug into a smoking-hot block. When things cooled off, the plug was really in there! Often, the square drive end twists off if you try removing it when stone cold. Try heating just the plug end with a torch, then shock-cool it with a candle held against the plug until the wax no longer melts. The plug now may nearly come out with your fingers. Putting the sender in the water pump has caused accuracy problems at higher engine speeds due to cavitation inside the pump- right about where the temp sensor sits.

Good luck and be patient- the thing is Italian!


I really appreciate the extended explanation above. With that in mind I will work through needed efforts, one at a time, to isolate the problem that I may still have. It's part of the fun of owning a Pantera. I may have been my own worst enemy by wire brushing the sending unit in an attempt to make it look nice and snew. The stem does appear a little loose, but it looks great. Stupid me. 

Yea, the Italians were masters of great architecture, art and automotive design, but function was not as high a priority. 

Thank you again.


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