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'66 Temp Gauge

12K views 63 replies 9 participants last post by  patrickstapler 
#1 · (Edited)
Recently replaced intake manifold, rebuilt carb, rebuilt distributor, replaced radiator with Spectre Premium CU-130, replaced water pump with Flowkooler, replaced thermostat with 195F Stant, removed block plugs and thoroughly flushed block, replaced all fluids new, installed new temp sending unit.

Issue: temp guage stays all the way on hot after warming up. Water temp at radiator stays right at 200F. Don't think guage is bad because temp stayed roughly in the middle of the gauge prior to all work being done.

Possible solutions???

 
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#5 ·
replaced thermostat with 195F Stant,

installed new temp sending unit.

Issue: temp guage stays all the way on hot after warming up. Water temp at radiator stays right at 200F. Don't think guage is bad because temp stayed roughly in the middle of the gauge prior to all work being done.
What temperature thermostat was in there before?

Why did you replace the sender?

Paul
 
#6 ·
Previous stat was also 195F. The sender that was in the original cast iron intake manifold had a larger hex on it and would not install next to the distributor in the Cobra intake. Luckily, the TU25 which shows to be the replacement has a much smaller hex.
 
#8 ·
It's likely just a badly calibrated sender. I've gone through three temp senders trying to find one that reads right on the gauge and actually just gave up. My current temp sender points at the "M" at 180*F, at the "P" at 195*F, and just past the "P" at 200*F. It's closer to "right" than the other senders were so that's the one that I kept.

The old temp sender PO put in my car was dead on perfect. The unfortunate part was that the thread was metric, so it leaked. Kind of liked the leak better than the bad gauge reading... :shrug:
 
#11 ·
…installed new temp sending unit.
All temp sending units on the market today are crap, and the indication on the gauge is what they do when the engine is normal.

What you need to do is find out the actual temperature. A temp gun will do the job, if you don't have one tape a digital cooking thermometer to the upper radiator hose. Don't let your wife catch you.

If the sender is the problem, and I'm betting it is, find a used original. They rarely go bad, and any old Ford engine will have one that is electrically correct, just make sure it's the right size.
 
#15 ·
All temp sending units on the market today are crap, and the indication on the gauge is what they do when the engine is normal.

If the sender is the problem, and I'm betting it is, find a used original. They rarely go bad, and any old Ford engine will have one that is electrically correct, just make sure it's the right size.
+1

All the following OEM sensor part numbers have been combined into a GENERIC unit sold aftermarket to fit the '65 Mustang:
3AF10884A, C3AF10884B, C3AF10884C, C3AZ10884A, C3AZ10884B, C3TF10884A, C3TF10884E, C3TF10884F, C3TZ10884A, C5DF10884A, C5DF10884B, C5DZ10884A, C5DZ10884B, D0TF10884B, D0TZ10884A, D1FZ10884B, D2TF10884AA
And, the following for 66 Mustang replacement:
C6DF10884A, C6DZ10884A, C6DZ10884B, C6MF10884A, C6MF10884B, C6TF10884A, C6TF10884B, C9WF10884A, C9WF10884B, D0HZ10884A, D0OF10884A, D0OF10884B, D0WF10884A, D0WF10884B, D0ZF10884A, D0ZF10884B, D2HF10884AA, D2WF10884AA, D2ZF10884AA, D5RY10884A, D9TZ10884A
 
#13 ·

As you face the back of the gauge, there are two calibration points. Lower left is adjusted with the ignition off to find true "zero"-"E" on a fuel gauge or "L" on a coolant temperature or oil pressure gauge. Upper right is adjusted with the ignition on with five volts of power to the gauge. This is where you adjust the needle for actual conditions. For example, "F" for a full tank or normal range with engine operating temperature at approximately 180-200 degrees F. Same is true for oil pressure.


Credit to Jim Smart for his MM article.:yoho:
 
#18 ·
I will say I am contemplating trying a BWD sensor to see if it reads any closer Thant the Standard Motor Products sensor which is installed. It's a $10 test versus removing the Rally-Pack, removing the instrument cluster and adjusting the gauge. However, I may have to do that as well because the oil pressure gauge also reads 0.
 
#20 ·
I am not going to sugar coat things, you can try both Napa premium and regular, BWD, SMP, Airtex, etc. All the aftermarket replacements are generic units made to be used across multiple applications and will not read accurately like the Ford OEM p/n calibrated for your gauge. Additionally the Ohm reading range will be different on a generic.

:cheers:
 
#21 ·
Wellllll...I went from one extreme to the other with the temperature sending unit. Swapped out the SMP which sat on the P at 200F water for a BWD which now sits on the T for 200F water. Guess I will reinstall the SMP and adjust the guage setting.

On a positive note, I took it to the exhaust shop today to install the 2 1/4" exhaust with Magnaflow X-Pipe and XL-3 mufflers. Very pleased with the sound at idle and WOT.

Also, seem to have fixed the vacuum leak at the carb base and manifold. Was able to adjust the idle air bleeds to roughly 17" Hg at roughly 800RPM. Guess I should be happy with that for a 50 year engine that have never been rebuilt.

Anyway, drove it to Costco for it's first fill up tonight. First real drive since refreshing the engine compartment, distributor and carb rebuilds and so on. I have to say, I'm pretty damn impressed with how it pulls, accelerates, and runs up to and above 5000RPM...again for a 50 year old engine.

I'm a firm believer in that whole distributor recurve thing...wow.
 
#22 ·
The way to go with the temp sensor is a used original Autolite™. Even a S/R Motorcraft™ would be fine. Easy to do, typically what goes wrong with temp sensors is physical damage or corrosion.
 
#23 ·
If I could find one of those that has the 1/8"PT and small hex is would use that. If you look back at the pic I posted, the original style with large PT and larger hex will not fit next to my distributor. I have two of the original style and they probably work as you say. They simply won't fit.
 
#27 ·
What do you mean by large body distributor? I didn't know there were two different sizes in '65/'66. It has a C50F prefix in the part number.

The two other larger hex sending units I have (which I have assumed to be Ford parts) would not require the bushing or adapter which I currently have as they have the correct PT for the intake manifold.
 
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