I finally got the temperature gauge working on the Mustang and it seems to run a bit hot according to the gauge.

The Mustang is a 66 with a I6 and it has a brand new 195 degree thermostat, I put this in because I was told it is the original replacement temperature.

The gauge quickly goes up to the P of the TEMP and then when the thermostat opens the temperature goes back down to between the E and M and then rises back up to the P and stays there.

Is this normal for this Mustang to be running that high on the gauge?

I am a little concerned since when I tested it today it was 4 degrees Celsius outside, 39 degrees Fahrenheit for you guys down south. I am worried that once the warmer temperatures arrive the car will run hotter.

What do you guys think, will it be okay?

Thanks

 

You can't depend on the stock gauge for any sort of accuracy. If you're concerned about it running too hot, you need to get a non-contact (infrared) thermometer on it, or install a mechanical gauge.

 

I intend to use the stock gauge, but will also do a simple calibration rather than just rely on the band on the gauge. Just remove the sender from the block and attach a wire to ground the sender and drop it into a pan of boiling water. Turn the key on and note where the gauge rises to. That would be 212 degrees. Now with a thermometer in the pan of water you can watch the gauge and note some temperatures for a few gauge readings. Like T=XXX deg, E=YYY deg, M=ZZZ deg and P=AAA deg. I did this same thing on my previous mustang and used the side burner on the BBQ grill to boil the water. Re-install the sender and now you will have a good idea what temp your engine is really at. BTW, if you use a non-contact thermometer, I would suggest pointing it at the thermostat housing for readings.

 

The stock guage in my car works just fine. Don't know why everyone seems to think they don't work. Just a couple thoughts though. Does the 66 have the restricter in the intake for the heater? If it does but, is missing, that could cause the guage to fluxuate. Could there be air in the system? The guage should go up til it gets to temp and stay...it should not go up and down. Maybe a plugged bypass? Or maybe even a plugged heater?

It just seems there is a flow issue. Like the coolant is flowing and stopping, instead of a steady flow. Maybe try a 180 therm.?

 

The stock gauges work, but they're not accurate, and often the resistance in the wiring increases. You can't say "my car is overheating" by looking at the stock gauge, unless you've benchmarked it like 109jb.

 

ya. when you have the same engine in 5 different car very one will show different temperature. as Tad says corroded connectors at firewall and elsewhere
i guess what you specify as "works fine" is that most of the time you drive the gauge points somehwhere in the middle ;-)

 

Thanks guys,

I will try and get some accurate temperature readings and correspond that to the gauge so I know the temperature is okay.

Just curious though, what is the normal range for these cars, since I have a 195 thermostat in there I know it should be somewhere around that temp but how hot is too hot? When should I be worried?

Thanks again

 

Maximum temperature that the coolant can stand is affected by a couple things. First is the mix. A 50/50 antifreeze/water mix boils at about 230 degrees at sea level as opposed to plain water at 212 degrees. The boiling point is raised further by putting the system under pressure like a pressure cooker. If you have a 15 psi cap it raises the boiling point about another 40-45 degrees. So the boiling point is now about 275 degrees. However, to provide a margin of safety I personally don't like to see over about 230. Right around the temp rating of the thermostat is ideal.

 

Actually, 200-210F is ideal for the engine. That's where the engine is designed to operate, and where you're getting good combustion in the chambers without causing damage to the engine. In a perfect world, you'd run the engine as hot as possible to avoid quenching the mix in the chambers, but the world isn't perfect and temps over 230F or so are likely to start causing damage to the motor.

 

Yeh, same gauge, same motor, same thermostat will read differently with different sending units. I have tried it. They are very much for a relative comparison. Find where normal operating temp is and make a mental note. If it goes higher than that, you are overheating. As mentioned above, you need a REAL gauge to really know what the temp is. I installed a set of AutoMeter water temp and oil pressure gauges, so I did not have to rely on the stock stuff.

I found that my car runs about 190 on the highway with a 180 thermostat. In traffic is will creep to 200 or so. When I was having overheating issues, it would regularly get 220. I agree that 220-230 is too hot and NOT normal.